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As wind‐borne migration of insects is strongly influenced by atmospheric circulation and weather systems, the relationships between insect population abundance and meteorological conditions are substantial. The brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the major wind‐borne insects hampering rice production in Asia, and its migration is significantly influenced by the Asian monsoon, a main component of the Asian climate system. However, the degree and mechanisms of the effects of monsoon on BPH migration have been little studied. In this paper, the effect of the Asian monsoon on the northward migration of BPH from the Indochina Peninsula to northern South China (NSC) was investigated based on the BPH light‐trap data and meteorological data for 39 years. The results show that the level of BPH migration in May could indicate the degree of annual pest outbreaks in NSC and that the southeast monsoon was more critical in this northward migration than the previously recognized southwest monsoon. The significance of the southeast monsoon stemmed from the strong effect of South China Sea subtropical high on BPH migration under a unique weather system distribution, the Polar low–Continental low–West Pacific subtropical high pattern. Furthermore, based on the key areas of migration obtained from the composite analysis, the multivariable linear regression prediction model could effectively predict the occurrence of BPH in NSC. These results indicate the importance of interactions between monsoons during BPH northward migration, which reflects the complex relationship between BPH migration and atmospheric motion. [ABSTRACT FROM AUTHOR]

Extreme summer precipitation often associated with flash floods has devastating impact on the local economies and livelihood of millions of people over East China. Tracking down the drivers of those extreme events will help to understand their formation mechanisms and to improve forecasts. Here the synoptic patterns associated with summer extreme precipitation events over East China during 1961-2018 have been identified systematically and quantitatively using a circulation clustering method. The results show that regional events over East China are dominated by the Eastern Asian summer monsoon associated Meiyu front, landfalling tropical cyclones and low-pressure vortices. Most sub-regions have seen increasing trends of extreme rainfall events during the past 6 decades with comparable contributions from the two main drivers. There was a decreasing trend over the North China Plain driven by the lowlevel southeasterly winds. Plain Language Summary Closely linked to flash floods, extreme precipitation is one of the high impacts but low probability weather phenomena that challenge modern numerical predictions. However, models are generally more skillful in predicting synoptic weather systems than precipitation itself. Taking East China as an example, this paper demonstrates the links between extreme precipitation events and synoptic weather systems using circulation clustering. Two major weather systems, the Eastern Asian Summer Monsoon and landfalling tropical cyclones are responsible for most extreme precipitation events (about 70%) over East China during the summer season. If models can accurately predict the strength and position of these weather systems, there may be enhanced potential of predicting regional precipitation extremes. Such implications are not regionally limited. [ABSTRACT FROM AUTHOR]

The roles of moisture sources and transport in intraseasonal precipitation variabilities during the preflood season over South China are complex and different. In this paper, ERA‐Interim reanalysis data that were collected four times daily from 1979 to 2017 are used to analyse the variation and influence of moisture transport in intraseasonal precipitation during the preflood season over South China. Using the Hybrid Single‐Particle Lagrangian Integrated Trajectory model, fixed atmospheric moisture sources are defined: land area source (LD source), Indian Ocean source (IO source), Pacific Ocean source (PO source), South China Sea source (SCS source), and South China source (SC source). Sea source moisture transport accounts for more than 75% of the total precipitation during the preflood season, which is the most important moisture source in South China. For April, southeasterly moisture transport, which includes PO source and SCS source moisture transports, is the major moisture transport over South China. Then, the IO source and SCS source precipitation increased significantly during May. During June, the IO source precipitation accounted for 43.75% of the total precipitation, thus dominating precipitation over South China. In addition, there is a significant difference in the interdecadal variation in the preflood season precipitation before and after the Indian summer monsoon onset. Before the Indian summer monsoon onset, the land‐sea thermal contrast decreased, which led to a significant interdecadal reduction in the IO source, PO source, and SCS source moisture transports. After the Indian summer monsoon onset, the increase in IO source moisture transport is the primary cause of the interdecadal increase in precipitation over South China. [ABSTRACT FROM AUTHOR]

In this paper, grain‐size records of 128 surface samples and six sediment cores retrieved from freshwater marshes across the Sanjiang Plain were employed to reconstruct the marshes' hydrological variation during the Holocene and to discuss its links to the East Asian summer monsoon (EASM) variation. The grain‐size hydrological significance for the marshes' deposits was first interpreted by quantitative analyses of 128 modern samples. The results indicate that the sand fraction exhibits a higher level significance to modern water‐level conditions than other grain‐size parameters. Thus, the sand accumulation rates of the six cores were calculated and employed to reconstruct the Holocene hydrological regime of the marshes on the plain. Based on the cluster analysis, it can be identified that three higher water‐level stages occurred during 6.2–5.6 thousand yr BP, 5.6–4.5 thousand yr BP, and 2.8–2.4 thousand yr BP, whereas four lower water‐level stages occurred during ~8.0–6.2 thousand yr BP, 4.5–2.8 thousand yr BP, 2.4–0.7 thousand yr BP, and 0.7–0 thousand yr BP, respectively. Considering the prevalent monsoon climate on the modern Sanjiang Plain, it is reasonable to believe that the local water‐level fluctuations were mainly regulated by the EASM variation rather than local factors including flooding, waterway modification, depression infilling, and human activities. The higher water‐level stages were linked to a stronger EASM and vice versa. This study provides essential background datasets for understanding the potential controls on the marsh development and degradation on the Sanjiang Plain. [ABSTRACT FROM AUTHOR]

Aim: Understanding the patterns and drivers of biodiversity across space and time is commonly based on species diversity, which may ignore species' functional role and evolutionary history and result in an incomplete understanding of community assembly. It is suggested that integrating species, functional, and phylogenetic diversity could provide a more holistic assessment of community assembly in natural ecosystems. This study aimed to explore the elevational patterns and environmental drivers of multiple facets of fish diversity and community structure in a subtropical river during the wet and dry seasons. Location: The Chishui River basin, China. Methods: We investigated the responses of fish species richness, functional richness, and phylogenetic diversity to elevation in different seasons. Moreover, we compared functional dispersion and mean pairwise distance with those obtained from null models to infer assembly mechanisms shaping community structure. Additionally, we examined the environmental drivers (e.g. water chemistry, temperature, and river size) of fish diversity and community structure. Results: Fish species richness, functional richness, and phylogenetic diversity showed a negative relationship with elevation in the Chishui River basin. Fish communities tended to be on average functionally random but phylogenetically clustered. Furthermore, phylogenetic structure exhibited a decreasing pattern along the elevational gradient. Despite no significant seasonal changes for fish diversity (except for phylogenetic diversity), fish communities became more phylogenetically overdispersed and clustered at low and high elevations in the dry season. Additionally, the responses of fish diversity and community structure to environmental variables were not synchronous. Conclusions: At the basin scale, environmental filtering was prevalent in shaping fish phylogenetic structure, whereas stochasticity was likely more important for functional structure. Moreover, the ecological mechanisms shaping individual fish communities switched from limiting similarity to environmental filtering as elevation increased, and the underlying forces at two ends of the elevational gradient became more prominent in the dry season. [ABSTRACT FROM AUTHOR]

Sensible heat flux greatly influences the Indian monsoon. In this study, we calculated sensible heat flux time-series for 12 sites over the western Tibetan Plateau using Price and Dunne's formula and adjusting the stability function. The time-series were derived from the field observations from the GEWEX Asian Monsoon Experiment (GAME)/Tibet programme under the Global Energy and Water Cycle Experiment (GEWEX). This paper demonstrates that monthly sensible heat fluxes show strong correlations with corresponding precipitation, and that the correlation coefficients increase with precipitation amount. The preceding winter and spring solid precipitation (snowfall and resulting snowpack) can also influence sensible heat flux in May, but the situation is complex. The correlations between heat flux and snowfall at Amdo, Naqu, and Lhasa are negative, but they are positive at Gaize (also known as Gerze) and Dingri. There is a significant relationship between how the variations from the mean calculated heat fluxes at Amdo differ from those at Rikaze, or Dingri, Cuona and Longzi, and their respective June-September precipitation amounts. This phenomenon may result from changes in circulation. When the sensible heat fluxes are above average north of the influence of the Indian monsoon and below average to the south, the summer monsoon circulation develops early and with greater intensity and precipitation, and vice versa. [ABSTRACT FROM AUTHOR]

In a previous study by the authors, a regional climate model (hereafter the RCM) developed to study the summer monsoon over South China (SC) and the South China Sea (SCS) has been tested and found to be able to simulate to a large extent the precipitation over this region for the months of May and June. To examine the interannual variability of the summer monsoon here, it is necessary to establish a model climatology to serve as a comparison and to reduce or even remove any systematic model biases. This paper presents the analyses of such a 10-year climatology (1991-2000). The model was initialized on 1 April and integrated up to the end of June for the ten years. The initial atmospheric conditions and lateral boundary data used in this study are from the European Centre for Medium-range Weather Forecasts '40-year' reanalyses. The RCM can reproduce well the main features of the monsoon circulation and vertical structure of the atmosphere. The RCM can simulate the intensification and northwestward displacement of the south Asian upper anticyclones from May to June, as well as the low-level moisture transport from the Bay of Bengal to SC. In the simulation, the average SCS summer monsoon onset occurs in the fourth pentad of May, which is consistent with the results from previous observational research. In addition, the RCM can reproduce the main characteristics of the onset such as the change of the low-level zonal flow from easterly to westerly as well as the rapid increase in daily precipitation. The SC and SCS precipitation anomalies have the correct sign in almost all the years. The shortcomings of the model simulation include an under-prediction of the strength of the subtropical high over the Northwest Pacific and the moisture transport from the Bay of Bengal to the Indochina Peninsula (IC) and SCS. A cold bias in surface air temperature is also observed, with the 10-year mean biases of the simulated surface air temperature over SC, SCS and IC in May and June being about −2.1 °C, −2.4 °C and −1.4 °C respectively. The 10-year mean biases of the simulated daily precipitation rate over SC, SCS and IC are about 2.0, −3.8 and 3.5 mm d−1 respectively. Copyright © 2005 Royal Meteorological Society. [ABSTRACT FROM AUTHOR]

The simulation skill of the perturbed parameter ensemble (PPE) of HadGEM3‐GC3.05 on the mean climate pattern of the Asian summer monsoon (ASM) is evaluated in this study. The sensitivities of the model bias to the perturbed parameters are investigated based on metrics. The results show that the PPE mean (PPE‐20M) could effectively capture the general ASM precipitation and wind patterns, with a correlation coefficient of 0.78. PPE‐20M mainly shows positive precipitation biases over the tropical western Pacific, southern slope of the Tibetan Plateau, Indochina Peninsula, and South China and negative precipitation biases over the Indian continent and Bay of Bengal. The magnitude of the precipitation biases is more sensitive than its pattern to the variation of the perturbed parameters. Four parameters (ent_fac_dp, qlmin, ps_cloud‐ph, and psm) are found to be crucial for simulating the ASM precipitation intensity, and their combined effects are related to the simulated precipitation biases. Plain Language Summary: The simulation of the Asian summer monsoon (ASM) has attracted much attention in recent decades. However, state‐of‐the‐art coupled models still show similar systematic biases when simulating monsoon precipitation from CMIP3 to CMIP6. Recently, a perturbed parameter ensemble (PPE) method has been applied in the development of HadGEM3‐GC3.05 with the aim of improving the overall simulation skill of the coupled model. The PPE can also be used to understand the related physical processes in the model simulations. Thus, in this study, we aim to evaluate the simulation skills of PPE on the mean climate distributions of ASM. Four parameters were found to be the most critical in the precipitation simulations, which could be potential tunable parameters to reduce the biases of precipitation intensity over the monsoon regions. This study provides possible pathways to reduce model bias that could benefit the model development community. Key Points: The perturbed parameter ensemble mean captures the climate pattern of the Asian summer monsoon (ASM) but mainly overestimates precipitation over the western PacificFour parameters (ent_fac_dp, qlmin, ps_cloud‐ph, and psm) are crucial for simulating ASM precipitation in coupled runThe joint effect of these parameters, especially the deep entrainment amplitude, are dominant control for the bias in the western Pacific [ABSTRACT FROM AUTHOR]

Convection is the main contributor to heavy rainfall over China's Yangtze‐Huai River Basin (YHRB) during Meiyu season; however, the mechanisms of convection initiation (CI) associated with the Meiyu front are still not well understood. In this study, a large set of 86,099 CI events, identified from composite reflectivity data in YHRB over six Meiyu seasons, were used to investigate the characteristics of the spatiotemporal distribution of CI in YHRB. The result showed that the overwhelming majority of CI events (∼90%) occurred in the region of existing stratiform clouds. Meanwhile, CI tended to concentrate in mountainous areas and exhibited two triggering modes. By relating the CI events with an objective analysis of ERA5 reanalysis data, it was also revealed that the characteristics of CI occurrence varied with patterns of Meiyu circulation and their interactions with local topography, and the warm air advection pattern dominated the Meiyu CI. We further illustrated that CI on the plains occurred with a morning peak corresponding to environments of high 0–3 km shear (SHR3) and low most unstable convective available potential energy (MUCAPE), while the CI near or over mountains had an afternoon peak corresponding to low SHR3 and high MUCAPE environments. Plain Language Summary: Convection occurs frequently in East Asian summer monsoon regions and brings a large amount of rainfall, especially over the Yangtze‐Huai River Basin in China during Meiyu season. Understanding the convection initiation (CI) process is crucial for forecasting subsequent precipitation and therefore has been an important research topic in regional/global climate and hydrological studies. Here, for the first time, we present a statistical analysis of a large quantity of CI events in the Yangtze‐Huai River Basin selected over six Meiyu seasons. This analysis revealed that about 90% of CI events during Meiyu were embedded in existing stratiform cloud bands, a distinct feature of the Meiyu CI from other types of CI. The hotspots, intensity, and diurnal cycle of CI events varied with large‐scale patterns of the dynamic and thermodynamic environment. These findings provide key information for improving our understanding of how convection initiates in the summer monsoon environment, which may lead to an improved forecast of convection‐related severe weather. Key Points: Convection initiation (CI) under Meiyu circulation occurs typically in the region of existing stratiform rainfall and exhibits two modesPatterns of Meiyu circulation, in conjunction with topography in the Yangtze‐Huai River Basin, regulate CI distributionOrographic CI is enhanced by the thermodynamic forcing in the afternoon while CI in the plains driven by the dynamic forcing in the morning [ABSTRACT FROM AUTHOR]

Numerous insects including pests and beneficial species undertake windborne migrations over hundreds of kilometers. In East Asia, climate-induced changes in large-scale atmospheric circulation systems are affecting wind-fields and precipitation zones and these, in turn, are changing migration patterns. We examined the consequences in a serious rice pest, the brown planthopper (BPH, Nilaparvata lugens) in East China. BPH cannot overwinter in temperate East Asia, and infestations there are initiated by several waves of windborne spring or summer migrants originating from tropical areas in Indochina. The East Asian summer monsoon, characterized by abundant rainfall and southerly winds, is of critical importance for these northward movements. We analyzed a 42-year dataset of meteorological parameters and catches of BPH from a standardized network of 341 light-traps in South and East China. We show that south of the Yangtze River during summer, southwesterly winds have weakened and rainfall increased, while the summer precipitation has decreased further north on the Jianghuai Plain. Together, these changes have resulted in shorter migratory journeys for BPH leaving South China. As a result, pest outbreaks of BPH in the key rice-growing area of the Lower Yangtze River Valley (LYRV) have declined since 2001. We show that these changes to the East Asian summer monsoon weather parameters are driven by shifts in the position and intensity of the Western Pacific subtropical high (WPSH) system that have occurred during the last 20 years. As a result, the relationship between WPSH intensity and BPH immigration that was previously used to predict the size of the immigration to the LYRV has now broken down. Our results demonstrate that migration patterns of a serious rice pest have shifted in response to the climate-induced changes in precipitation and wind pattern, with significant consequences for the population management of migratory pests. [ABSTRACT FROM AUTHOR]

Climate change impacts ocean nutrient availability and will likely alter the marine food web. While climate models predict decreased average ocean productivity, the extent of these changes, especially in the marginal seas upon which large human populations depend, is not well understood. Here, we reconstructed changes in seawater phosphate concentration and nitrate source over the past 400 years, which reveals a more than 50% decline in residence time of seawater phosphate, and 8%–48% decline in subsurface nitrogen supply following the coldest period of Little Ice Age. Our data indicates a link between surface ocean nutrient supply and the East Asian Summer Monsoon strength in an economically important marginal sea. As climate models predict that the East Asian Summer monsoon will strengthen in the future, our study implies that surface ocean primary productivity may increase in the South China Sea, contrary to the predicted decrease in global average ocean productivity. Plain Language Summary: Global climate models predict that surface ocean nutrient concentrations will significantly decrease over the next 100 years as our climate changes. However, in the world's marginal seas, which human populations depend on most heavily for food security, the surface ocean biogeochemical changes are still difficult to predict with global‐scale models. Here, using coral‐based paleoclimate proxies, we reconstruct changes to surface phosphate concentration and to sources of surface nitrogen over the past four centuries in the South China Sea (SCS). Combined with box model simulations, our data reveal a more than 50% decline in phosphate residence time and an 8%–48% decline in subsurface nitrate supply from the 1600s to present. Such a decline implies a significant decrease in primary productivity and likely a community shift toward nitrogen‐fixing phytoplankton. Importantly, our data indicate that the decrease in nutrient supply was driven by weakened monsoon‐induced upwelling, demonstrating strong ties between nutrient supply and monsoon strength in the SCS. Climate change is predicted to strengthen the East Asian Summer Monsoon, and our results suggest that primary productivity in this economically important region may increase, contrary to the widely predicted decreases in average global ocean productivity. Key Points: Coral skeletal phosphorus content with scattered nitrogen isotopes is reconstructed over the past 400 yearsNutrient supply declined up to 48% since the Little Ice Age in the western South China SeaThe coral record from links nutrient supply to monsoon wind, implying higher productivity under a stronger monsoon in the future [ABSTRACT FROM AUTHOR]

The generalized complementary relationship (CR) of evaporation was investigated in the irrigated winter wheat/summer maize double‐cropping sites in North China Plain (NCP), a region influenced by the East Asian dry winter and wet summer monsoon. Different generalized CRs exist in the winter wheat (dry) and summer maize (wet) seasons with abrupt changes in June and October. The seasonal abrupt change in the CR is attributed to the sudden reversed water vapor transport with the winter and summer monsoon and the wheat/maize rotation with irrigation in the winter wheat season. The separation and abrupt change in the complementary behavior require that two‐stage phased parameters corresponding to the wheat (dry) and maize (wet) seasons should be adopted by the generalized complementary functions for operational evaporation estimation in the irrigated double cropping NCP. Plain Language Summary: The irrigated double cropping North China Plain (NCP) is characterized with rapid winter wheat/summer maize rotation on the land surface and sudden reversed water vapor transport in the upper‐air with East Asian monsoon, coincidentally in June and October. There are corresponding abrupt changes of the complementary relationship, a theory relating changes in landscape evaporation and atmospheric evaporation demand. It reveals the impacts of the processes related to large‐scale changes in atmospheric circulations on the complementary behavior and the requirement of different parameters during the two stages for operational evaporation estimation using the complementary principle in the irrigated double cropping NCP. Key Points: Different generalized complementary relationships (CRs) exist in winter wheat and summer maize seasons with an abrupt changeAbrupt change of the CR is mainly attributed to upper‐air circulations with East Asian monsoonWheat season irrigation contributes to the abrupt change via interrupting the connection between land surface and atmosphere [ABSTRACT FROM AUTHOR]

The first rainy season (April–May–June) extreme precipitation events over South China tend to frequently occur in specific hotspots, resulting in a great threat to local society and economy. Abundant moisture supply is essential to precipitation formation. In this study, we employ the FLEXPART model to investigate the geographical moisture sources for extreme precipitation events in three hotspots of Guangdong from west to east (termed as Area‐A, B, and C). During both the periods before and after the onset of the South China Sea Summer Monsoon (hereafter SCSSM), the moisture contributions of ocean regions are larger than that of land regions for all the hotspots, but the main moisture source regions are different. Before the onset of SCSSM, the main source regions are South China Sea and Southeastern Asia, which contribute 36.50 and 31.79% to Area‐A, 35.85 and 27.83% to Area‐B, while 42.27 and 23.81% to Area‐C, respectively. After the onset of SCSSM, the contribution of moisture from Indian Ocean increases a lot. Thus, the main source regions are Indian Ocean, Southeastern Asia and South China Sea, which contribute 31.52, 24.58 and 18.13% to Area‐A, 29.21, 21.82 and 14.99% to Area‐B, 26.62, 20.70%, and 28.19% to Area‐C, respectively. Among the three hotspots, the contribution of ocean regions for Area‐C is the largest. Southeastern Asia is the main land contributor before and after the onset of SCSSM for all the hotspots. This study implies the important role of both ocean and land moisture sources on extreme precipitation variations over South China. [ABSTRACT FROM AUTHOR]

ABSTRACT Climate is a primary driver for extreme rainfall and flood events. In this paper, the temporally changing flood risk associated with the annual maximum 30-day rainfall (30-day AMR) and the annual maximum daily inflow ( AMDI) related to the Xidayang Reservoir catchment is analysed from a climatic context. This is the largest catchment in Daqing River Basin in North China and is highly prone to floods related to the East Asian summer monsoon. Two climate factors, the average May-June-July sea surface temperature anomalies in areas of the northern Indian Ocean and western Pacific Ocean, are identified. They show a high negative correlation with the AMDI and 30-day AMR. Bayesian nonstationary models are then developed for the AMDI and 30-day AMR using the climate predictors identified as covariates. We compared three types of models of AMDI and 30-day AMR: (1) time-invariant, (2) linear temporal trend and (3) climate informed, and found that the climate-informed models exhibit the best performance according to Deviance Information Criterion (DIC) and 90th percentile Bayesian coverage rate for both AMDI and 30-day AMR. A significant decreasing trend is identified in the AMDI and the 30-day AMR, which is found to be associated with the climate predictors. Leave one out cross validation (LOOCV) is used to demonstrate that these models have decent skill in predicting year-to-year variability in flood risk. This can help to provide flood/rainfall dynamic management measures for reservoirs in Daqing River Basin using information from before the beginning of monsoon season, thus facilitating adaptation to a changing climate. [ABSTRACT FROM AUTHOR]

In the East Asian monsoon region, eolian deposits widely distributed in the middle-lower reaches of the Yantgze River are among the best materials available for studies on Quaternary climate change in the subtropical zone of Southern China. Typical eolian deposits in this region include upper Xiashu Loess (XL) and underlying Vermiculated Red Soil (VRS) layers. In this paper, chronological and paleoclimatic studies are conducted on an eolian deposit sequence near Jiujiang (JJ) city in northern Jiangxi province. A magnetostratigraphic study, combined with optically stimulated luminescence (OSL) dating, is conducted on the JJ section and provides further evidence that eolian deposits in the middle-lower reaches of the Yangtze River have been formed since the late Early Pleistocene, and that the boundary age between the XL and VRS layers is about 300-400 kaBP. In grain-size records of the JJ section, the median grain-size and content of the >30 μm size fraction increase sharply after 300-400 kaBP, representing an East Asian winter monsoon intensification event. Further pollen analysis reveals differing pollen assemblages before and after 300-400 kaBP: there is an evident increase in plants adapted to grow in a warm humid environment after 300-400 kaBP, implying an increase in precipitation caused by intensification of the East Asian summer monsoon. Global ice volume and uplift of the Tibet Plateau (TP) are regarded as crucial factors influencing variations of the East Asian monsoon on a long-term scale. The deep-sea δ18O record, which reflects variations in global ice volume, shows no obvious change after 300-400 kaBP. Moreover, the influence of global ice volume changes on the East Asian summer and winter monsoons is inverse; the global ice volume increase (decrease) implies a strengthened (weakened) winter monsoon and weakened (strengthened) summer monsoon. We therefore interpret the coupled intensifications of the East Asian summer and winter monsoons at about 300-400 kaBP to the uplift of the TP in the Middle Pleistocene. This climate event is also documented in eolian deposits from the southern margin of the Chinese Loess Plateau (CLP) and from the desert-loess transitional belt. However, it is not recorded in the loess-paleosol sequences from the central part of the CLP, thereby indicating differing climate responses to TP uplift in different regions, which requires further study. [ABSTRACT FROM AUTHOR]

The large‐scale flows and rainfall pattern change markedly with the progression of the summer monsoon, but how the convective and microphysical characteristics of monsoon extreme precipitation vary subseasonally remains elusive. This study compares 16,844 extreme precipitation features (EPFs) among the pre‐monsoon, active‐monsoon, post‐monsoon periods, and tropical cyclone (TC) days using multisource data including dual‐polarimetric radar observations over the Pearl River Delta in South China. Results indicate that the environmental dynamics and thermodynamics significantly influence the EPFs' convective and microphysical properties. Despite the similar environmental conditions such as abundant moisture and moderate to large convective available potential energy (CAPE) under which the EPFs occur, differences among the four periods are noticed. During the pre‐monsoon period, precipitation systems are the largest in area but their EPFs are the least frequent and have the lowest raindrop concentration, likely due to the colder and drier environment with large vertical wind shear (VWS). The onset of the summer monsoon increases both the frequency and the convective intensity of EPFs, leading to an increase in raindrop size, which is consistent with the substantial increases of CAPE and moisture during the active‐monsoon period. The EPFs share similar convective intensity and raindrop size distribution (RSD) between the post‐monsoon and the active‐monsoon periods, although the post‐monsoon EPFs are slightly less frequent and have a smaller horizontal scale related to the reduced 0–6‐km VWS. Interestingly, EPFs associated with TCs have the weakest convective intensity but the most active warm‐rain processes with the RSD being closer to the maritime regime. Plain Language Summary: Extreme precipitation is of great concern due to its disaster‐causing properties. With the evolution of East Asian summer monsoon, the large‐scale atmospheric circulation and main rain band change subseasonally. We would like to know how the convective and microphysical characteristics of extreme precipitation in monsoon regions vary during the monsoon evolving stages and under the influence of tropical cyclones (TCs). To document the microphysical characteristics of extreme precipitation, we use 4‐year, high‐resolution observations from a dual‐polarization radar on a typical monsoon coast (South China). Results show that, after the onset of summer monsoon, the extreme precipitation events occur much more often, their probability distribution of convective intensity shifts toward more intense convection, and ice water content increases. When the monsoon rain band moves northward to influence central East China, extreme precipitation at the South China coast is mainly produced by locally developed, small‐size storms with convective intensity comparable to those during the prior, active‐monsoon period. Compared to those during the three stages of monsoon activity, the extreme precipitation events in the vincinity of TCs' circulation have lower strong‐echo tops with rain drop size distribution closer to the "tropical maritime type" of convective precipitation. Key Points: The onset of monsoon quadruples the occurrence frequency and enhances mixed‐phase processes of extreme precipitation features (EPFs)The post‐monsoon EPFs possess similar convective intensity to the active‐monsoon EPFs but smaller size related to the reduced vertical wind shearThe TC‐day EPFs have the weakest convection but the most active warm‐rain processes with smaller convective available potential energy and thicker warm cloud layer [ABSTRACT FROM AUTHOR]

Pressure on river water resources may increase continuously under global climate change and the increasing intensity of human activity, and the identification of river water sources is needed to maintain water resource sustainability. In this study, river water sources were studied using hydrochemical tracers (i.e. the major ions) and end‐member mixing analysis (EMMA) during two hydrological years, in the subtropical monsoon basin of the Xiangjiang River in the south‐central China. Various water types including precipitation, river water, and mountain creek water, were collected in the basin at a high frequency. The results of EMMA showed that the average contributions from the direct input of precipitation, near‐surface runoff (represented by mountain creek water), and groundwater (represented by river water sampled during the base flow period) were 28 ± 24%, 49 ± 24% and 23 ± 16%, respectively. The contributions from these water sources to the river water varied greatly within the year, which may indicate a shift in the major flow pathways from direct precipitation input and near‐surface flow pathways in the spring rainy months (e.g. from March to May), to a deeper flow pathway in the dry or rainless months (e.g. January, February, July and December). The shift of the major flow pathways may be due to the factors such as the seasonality of precipitation, evapotranspiration and soil wetness conditions. Groundwater and near‐subsurface runoff dominated the river water and the direct input of precipitation was negligible during the dry or rainless months, and consequently, the river water chemistry was less diluted and more influenced by water‐soil/rock interactions and anthropogenic pollution during these months. The creek water contribution to the river water was relatively high in summer, especially in June and July 2021, which may indicate the substantial inter‐seasonal carryover of precipitation that contributed to the river water. With the projected increased frequency of extreme weather events such as seasonal drought, streamflow in the subtropical monsoon regions may experience greater recharge by deeper flow pathways, with the enhanced role of base flow in regulating streamflow, and there may be an increased risk to the water resource security under the condition of the decreased river dilution capacity and increased anthropogenic pollution. [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon (EASM) is unique among monsoon systems that it features meridional evolution of the summer monsoon. In this study, we evaluate the performances of a Variable‐Resolution Community Earth System Model (VR‐CESM) regionally refined over eastern China (14 km) in reproducing the seasonal evolution of EASM precipitation over China. Compared with reference datasets, VR‐CESM shows better performance than the corresponding globally uniform coarse‐resolution model CESM (quasi‐uniform 1°), especially over western China where complex local topography exists. The northward monsoon migration is closely related to low‐level southerly flows and vertical moisture advection, which are more reasonably simulated in VR‐CESM. The four critical timings of the EASM (monsoon onset, withdrawal, peak, and duration) are also better captured in VR‐CESM than in CESM. The corresponding spatial Pearson correlation coefficients of the four critical timings with respect to reference datasets are about 0.1 higher in VR‐CESM than those in CESM. Both models are most accurate in simulating monsoon onset and least accurate at simulating the monsoon peak. The overestimated zonal thermal contrast in CESM is responsible for the earlier monsoon onset and excessive precipitation in September over the Yangtze River valley. Finer resolution in VR‐CESM, especially over the Tibetan Plateau (TP), appears to be a main factor in simulating better zonal thermal contrast and seasonal evolution of the EASM. [ABSTRACT FROM AUTHOR]

A heavy rainfall trajectory (HRT) is defined as the trajectory formed by the movement of the rainstorm centre of a heavy rainfall event over time. Based on this definition, the dispersion degree (DD) of HRTs is applied based on the Euclidean distance and an empirical orthogonal function (EOF) to quantify the spatiotemporal distribution and evolution characteristics of HRTs in China. The results show that (a) the spatial distribution and length of HRTs in China have distinct geographical and seasonal characteristics, which are strongly influenced by the East Asian summer monsoon. (b) From southeast China to northwest China, the DDs increased to 8 and the length of HRTs decreased by 53,925 m. (c) According to EOF analysis, the direction angle change of northeast‐oriented HRTs shows a significant negative trend across the country, while those of southeast‐, southwest‐ and northwest‐oriented HRTs show a significant positive trend. From 2008 to 2019, HRTs flattened in the northeast and southwest directions, while HRTs steepened in the southeast and northwest directions. This research provides certain scientific guidance for the prevention and mitigation of regional disasters and provides necessary theoretical support for the changing patterns of the climate system under the impact of climate change. [ABSTRACT FROM AUTHOR]

Zooplankton fecal pellets play a significant role in particulate organic carbon (POC) export, which has been widely reported in different ocean regions. However, zooplankton fecal pellet in the tropical marginal sea and its contribution to the total POC flux has not been sufficiently investigated yet. Here, for the first time we report zooplankton fecal pellet characteristics and fluxes in the South China Sea from June 2020 to May 2021 via one mooring with two sediment traps deployed at 500 and 2,190 m depths. Average fecal pellet numerical flux was 2.30 × 104 and 4.22 × 104 pellets m−2 d−1 at 500 and 2,190 m, respectively, corresponding to average fecal pellet carbon (FPC) flux from 0.31 to 0.71 mg C m−2 d−1. Small ellipsoidal and spherical pellets accounted for more than 90% of the total numerical flux, while large cylindrical pellets, although relatively rare (6%), accounted for almost 15% of the FPC flux. Both fecal pellet numerical and carbon fluxes were higher in winter, when the strong East Asian winter monsoon winds and heavy rainfall promoted the marine primary production. Higher fecal pellet fluxes combining with the presence of extra‐large pellets at 2,190 m compared to those at 500 m suggested the in‐situ repackaging of deep‐dwelling zooplankton communities in the mesopelagic and bathypelagic zones. Contribution of fecal pellets to the total POC flux ranged from 0.4% to 30.0% (averaging 9.0%), with higher values occurring during winter monsoon, at which time fecal pellets became a critical conveyor of carbon export to the deep sea. Plain Language Summary: Zooplankton fecal pellets sinking from the sea surface and water column constitute an important component of the marine biological pump. Time series study of fecal pellet flux is therefore of great importance to investigate the deep‐sea particulate organic carbon export. In this study, we examined the temporal and spatial variation of fecal pellet flux in the tropical marginal sea for the first time. Fecal pellet numerical flux and carbon flux at 500 and 2,190 m water depths in the southern South China Sea were quantified, which exhibited great seasonal signals and vertical changes. Strong East Asian winter monsoon contributed to higher fecal pellet fluxes through strengthening the water column mixing and enhancing the marine primary production. In‐situ repackaging of deep‐dwelling zooplankton communities were responsible for the increased fecal pellet flux in the deep sea. Our result of zooplankton fecal pellet flux in the southern South China Sea reflects a dynamic balance between the marine primary production, zooplankton consumption, recycling process, and in‐situ production. Therefore, this study confirms the significant role that zooplankton fecal pellet plays in the local carbon export and provides new insight into the biogeochemical cycling in the tropical marginal sea. Key Points: Zooplankton fecal pellets constitute 0.4%–30.0% of marine particulate organic carbon flux in the deep southern South China SeaStrong East Asian winter monsoon promotes the growth of zooplankton communities and increases their fecal pellet fluxesRepackaging of deep‐dwelling zooplankton communities in mesopelagic and bathypelagic zones contribute to enhanced deep‐sea carbon export [ABSTRACT FROM AUTHOR]

Aim: The interspecific relationships between species occupancy and abundance have been broadly studied in terrestrial systems; however, the causes underlying this relationship in freshwater fishes remain poorly addressed. The main aims of this study were (a) to examine the occupancy–abundance relationship in 62 fish species in a monsoon climate river; (b) to determine the relative importance of species niche, functional traits and phylogenetic relatedness in shaping the occupancy–abundance relationship. Location: The Chishui River, the Yunnan‐Guizhou Plateau and the Szechwan Basin, China. Taxon: Freshwater fishes. Methods: A linear model was used to test the relationship between distribution and mean abundance across fish species. The outlying mean index analysis was performed to estimate niche breadth and niche position parameters for each fish species. In addition, using principal coordinates analysis, we created four trait vectors describing the similarity of species' traits. Fish phylogeny was obtained from a global molecular phylogenetic tree of actinopterygian fishes. We used a combination of linear models, commonality analyses and boosted regression trees to evaluate the relative effects of the niche metrics, traits and phylogenetic relatedness on occupancy and abundance. Results: Fish occupancy was strongly (R2 = 0.749) and positively correlated with mean abundance in the Chishui River. Niche parameters, especially niche position, were the main determinants of variation in occupancy (e.g. total contribution of niche position and breadth using commonality analyses: 0.587 and 0.318) and abundance (0.323 and 0.151) across species. Furthermore, traits and phylogeny had little to no effect on fish occupancy (0.034 and 0.037) and abundance (0.021 and 0.003). Main conclusions: Freshwater fishes in the Chishui River fit the common macroecological pattern of positive relationship between occupancy and abundance. Niche parameters, but not traits and phylogeny, are the primary correlates of riverine fish distribution and abundance. [ABSTRACT FROM AUTHOR]

Studies have shown that East Asia experienced several abrupt centennial‐scale weak monsoonal events in the early Holocene. However, the timing and structure of these climate events remain unclear due to the lack of precisely dated and highly resolved records. In this study, we present a well‐dated high‐resolution East Asia summer monsoon record from 11.32 to 10 ka BP based on two coeval stalagmites, one of which developed clear annual lamina, from Shihua Cave, northern China. Stalagmite δ18O records show 2 weak summer monsoon events at 10.9 and 10.3 ka. The 10.9‐ka event occurred from 10.93 to 10.79 ka BP for ∼140 years and features a "W"‐shaped structure. The 10.3‐ka event, also known as the ice‐rafted debris event 7 in the North Atlantic, lasted ∼260 years with an asymmetric double‐plunging structure. The two events are concurrent with the cold conditions in Greenland ice core record, indicating a close correlation between East Asia summer monsoon and North Atlantic climate. Spectral analyses on Shihua Cave stalagmite δ18O time series and annually lamina thickness sequence both show a statistically significant periodicity of 200 years, indicating that anomalous climate events may be triggered by solar activity. The 10.3‐ka event also coincides with three small freshwater outbursts in the high‐latitude North Atlantic. This agreement suggests that freshwater outbursts may have played a role in reinforcing this weak 10.3‐ka event in monsoonal China. Key Points: 3‐year resolved δ18O record derived from lamina stalagmites in northern China details the East Asia summer monsoon (EASM) history from 11.32 to 10 ka BPTiming and structure of 10.9 and 10.3 ka weak monsoon eventsThe 10.9 and 10.3 ka weak EASM events are linked to high latitudes climate via atmospheric teleconnection and associated with solar changes [ABSTRACT FROM AUTHOR]

The evolution of hydroclimate in East Asia during the Pliocene—a potential analog of the future greenhouse climate—remains highly uncertain. Here we reconstruct changes in the hydroclimate of Northern China during this epoch. Our results reveal previously undocumented severe drought conditions that persisted through the early Pliocene with a significantly greater magnitude than suggested by other records. Using a broad hierarchy of climate simulations, we find that reduction in the Pacific meridional sea surface temperature (SST) gradient has particularly strong impacts on precipitation over Northern China, which suggests its key role in maintaining drought conditions during the early Pliocene. The weaker Pacific meridional SST gradient causes the weakening of the East Asian summer monsoon precipitation over this region via a reduction of atmospheric northward moisture transport from the ocean, which enhances aridity inland. Our results highlight the fundamental control of the tropical ocean on the extra‐tropical hydrological cycle. Plain Language Summary: Understanding East Asian rainfall changes with global warming is an important issue of climate sciences. The Pliocene epoch provides a potential analog to the future greenhouse climate. Here, for the first time we reconstruct high‐resolution aridity changes over the Chinese Loess Plateau (CLP) in northern East Asia during the Pliocene. Our results indicate persistent drought conditions over CLP during the early Pliocene. Analyzing a broad range of climate model simulations, we find that the reduced meridional sea surface temperature gradient is a critical factor in the weakening of the East Asian summer monsoon over Northern China and in maintaining drought conditions during the early Pliocene relative to the late Pliocene. Our results expand the Asian inland paleoclimate records during the Pliocene, providing new information on past Asian monsoon precipitation variations during the warm Pliocene with potential implications for future hydroclimate changes under greenhouse warming in East Asia. Key Points: Severe drought conditions persisted throughout the early Pliocene epoch over Northern ChinaWe link these conditions to the reduced meridional temperature gradient in the Pacific OceanThe reduced Pacific meridional temperature gradient acts to weaken the summer East Asian monsoon precipitation over Northern China [ABSTRACT FROM AUTHOR]

Paleoclimatic records reveal spatially asynchronous changes of East Asian summer monsoon (EASM) precipitation during the Holocene, but the underlying mechanisms are not fully understood. This study explores the role of the zonal shift of the Asian westerly jet (AWJ) core on the spatial‐temporal variability of EASM precipitation based on Holocene climate simulations using the KCM and CESM forced by orbital variations. We analyzed the composite differences of summer precipitation and associated atmospheric circulations between the early (middle) and middle (late) Holocene. Simulations suggest a dipole pattern of summer precipitation with increasing (decreasing) precipitation in central (southern) China from the early to late Holocene, which was shaped by the eastward shift of the AWJ core. The eastward shift of the AWJ core and the accompanied eastward movement of the upper‐level convergence over the AWJ's right exit region weakened the low‐level downward motions over central China. Meanwhile, the low‐level upward motions over southern China were weakened by the concurrent eastward (westward) migration of the South Asian High (western Pacific subtropical High) during the Holocene. Consequently, summer precipitation increased (decreased) in central (southern) China from the early to late Holocene. The eastward shift of the AWJ core was primarily driven by amplified meridional insolation gradient at middle latitudes via strengthening upper‐level westerly intensity during the Holocene. In addition, land cover difference between East Asia and central Asia caused a greater enhancement of westerlies intensity in East Asia, further modulating the eastward movement of the AWJ core during the Holocene. Key Points: Our simulations reveal a dipole pattern of summer precipitation between central and southern China during the HoloceneThe dipole precipitation pattern was strongly modulated by zonal shift of the Asian westerly jet coreInsolation variation and land cover caused the eastward shift of the Asian westerly jet core during the Holocene [ABSTRACT FROM AUTHOR]

Eastern China is perennially hit by mesoscale convective systems (MCSs), yet it remains an open question as to whether and how their general properties change throughout the annual cycle. By leveraging high‐resolution satellite observations and a hybrid tracking algorithm, we present a 20‐year (2001–2020) climatology of MCSs over eastern China during eight subseasonal‐to‐seasonal (S2S) monsoon stages. MCSs contribute up to 50% of the stage‐total precipitation and over 60% of the rainband‐zone precipitation during the Pre‐Meiyu and Meiyu episodes, and their contributions remain non‐trivial during the transition seasons. We discover two contrasting regimes of MCSs that alternate immediately upon the Pre‐Meiyu and the Fall onsets. The wintertime regime features fast‐propagating shallow systems initiated at night in a strongly sheared and dry environment. The summertime regime, instead, features an outbreak of MCSs in the south, where the systems often initiate in the afternoon and propagate 2–3 times slower than the cold‐season ones. Based on multivariate clustering analysis, the nighttime MCSs that dictate the winter stages often initiate over a deep nocturnal boundary layer with moist rear inflows upgliding above it. In contrast, the afternoon‐initiated MCSs under the summertime regime feature a pronounced convective available potential energy (CAPE) "tongue" and upslope flows in their southeast quadrant. The southwesterly moist ascending flows are likely to shallow the convective inhibition at the tip of the CAPE tongue and facilitate the intense updrafts of the MCSs. Findings here may offer insights into S2S weather prediction and facilitate agricultural and water management throughout the year. Plain Language Summary: Eastern China has been one of the worst‐hit regions globally by extreme precipitation and floods. Many of these hazards result from intense and well‐organized rainstorms, also known as mesoscale convective systems (MCSs), typically lasting for several hours with a horizontal scale of 100 km or larger. Despite numerous case studies on their evolution and dynamics, the annual cycle of the impacts and properties of MCSs is yet to be fully understood. Using high‐resolution satellite observations and a hybrid tracking algorithm, we present a 20‐year (2001–2020) climatology of MCSs in eight monsoon stages year‐round. We discover a dual regime wherein two distinct regimes of MCS characteristics are observed throughout the annual cycle. It turns out that MCSs can contribute up to 50% of the stage‐total precipitation and over 60% of the rainband‐zone precipitation during the pluvial episodes, and their contributions remain non‐trivial during the transition seasons. The prevailing environmental conditions at the initiation of MCSs are revealed and discussed. Findings from the present study help broaden our understanding of the annual cycle of MCSs and may offer insights into numerical weather simulations and prediction, water and agricultural management, and disaster risk reduction in eastern China. Key Points: An unprecedented monsoon‐annual‐cycle climatology of mesoscale convective systems (MCSs) in eastern ChinaDiscovery of two contrasting regimes of MCSs that alternate upon the Pre‐Meiyu and Fall onsetsMoist rear inflows, static instability, upslope flows, and cold pool‐shear interactions are recurring in convective initiation [ABSTRACT FROM AUTHOR]

This study investigates inter‐model spreading of changes in East Asian winter monsoon circulation and the underlying reasons under 1.5 and 2.0°C global warming for Representative Concentration Pathway 8.5. Results show that the spatial patterns of multi‐model ensemble and inter‐model spreading of changes in 850‐hPa zonal and meridional winds over East Asia are similar under the two global warming targets. The multi‐model ensemble changes in 850‐hPa meridional wind (V850) over southern China are near zero under the two targets. Meanwhile, the V850 changes over southern China exhibit large inter‐model spreading, which is closely related to those of regional differences in sea surface temperature changes (DSSTC) in the tropical Pacific. Models with positive V850 anomalies over southern China tend to project weak (strong) surface warming in the western North Pacific (South China Sea and the equatorial central and eastern Pacific). Such a configuration results in decreased precipitation over the east of the Philippines and hence an anomalous lower‐level high to its northwest. Accordingly, southwesterly anomalies prevail over southern China. The southwesterly anomalies are further enhanced by related positive feedback processes. Models with negative V850 anomalies tend to project strong (weak) surface warming in the western North Pacific (South China Sea). The projected surface warming in the equatorial central and eastern Pacific is also strong, but weaker than that of models with positive V850 anomalies. Therefore, the induced precipitation and circulation changes over the East Asia–western North Pacific are basically opposite to those described above. Besides, the inter‐model spreading of V850 changes over southern China decrease by about 36.2% from 1.5 to 2.0°C global warming, which can be partly attributed to the decrease in the inter‐model spreading of DSSTC in the tropical Pacific. Numerical experiments confirm the role of the sea surface temperature changes in the tropical Pacific. [ABSTRACT FROM AUTHOR]

Most western Northwest China (WNWC) has experienced notable wetting in recent decades. Despite the widespread attention of scientific community, the causes of such climate shift are still not well‐understood. In this study, we find that the dominant mode of Indian Ocean sea surface temperature variability — Indian Ocean Basin mode (IOBM) plays a crucial role in the precipitation over WNWC. Nonetheless, such a close lagged relationship is unstable, and varies with Pacific Decadal Oscillation (PDO). When the PDO is in its warm phase, there is no robust lagged relationship between April‐June WNWC precipitation variations and January‐March IOBM. When the PDO is in its cold phase, the warm phase of the IOBM inspires a wavetrain across the Eurasian continent in the next April‐June, with an uncommon low pressure around Lake Baikal, thereby enhancing the westerlies and thus more moisture into the WNWC region. This enables the IOBM‐based statistical rainfall prediction scheme to estimate the precipitation in the WNWC region with some confidence. This remarkable contrast in the influence of IOBM between the two phases of the PDO highlights exciting new avenues for improving climate predictions over the WNWC. Plain Language Summary: The preceeding January‐March Indian Ocean Basin mode (IOBM) plays a crucial role on early summer precipitation in WNWC. But such high lagged‐relationship is not stable and varies with the Pacific Decadal Oscillation (PDO). When the PDO is in warm phase, there is no robust lagged‐relationship between April‐June WNWC precipitation variations and January‐March IOBM. While the PDO is in cold phase, the warm IOBM inspires a wavetrain across Eurasian in next April‐June, with an anomalous low pressure around Lake Baikal, thereby enhancing the westerlies and thus more moisture into WNWC region. So is the success of an IOBM‐based statistical rainfall prediction scheme on WNWC. Key Points: Indian Ocean Basin mode (IOBM) in preceding Jan‐Mar plays a crucial role on the Apr‐Jun precipitation in western Northwest China (WNWC)The close lagged relationship between IOBM and WNWC precipitation is unstable, and varies with Pacific Decadal Oscillation (PDO)The IOBM‐based statistical rainfall prediction scheme on WNWC has a high predictability during the cold phase of PDO [ABSTRACT FROM AUTHOR]

The monsoon development in the early rainy season in East Asia is analysed by the evolution of daily weather types (WTs). The WTs are classified by a k‐means clustering analysis based on 850 hPa winds from April 1 to July 31 in the 40‐year period of 1979–2018. Five WTs are identified, typifying the progression of weather regimes in the monsoonal evolution. WTs 1 and 2, with easterly winds in the South China Sea (SCS), occurs mostly in April and early May, corresponding to typical WTs before the SCS monsoon onset. In WT3, winds in the SCS turns westerly, and a rain band emerges in South China, extending east‐northeastward to the Pacific Ocean south of Japan, which signifies the May–June Mei‐yu in South China. Then, with the rain band moved to Yangtze River Valley (YRV) in WT4, this WT corresponds to the June–July Mei‐Yu in central and eastern China along the YRV. Finally, WT5 occurs more frequently towards the end of July, and corresponds to the post‐Mei‐Yu WT, indicating the ending of the early summer rainfall season in East Asia. The evolution of the WTs is gradual but intermittent, representing the weather‐within‐climate information. Each WT likely persists to itself. But WT1 and WT2 also progress to each other. The long persistence of WT3 and WT4 up to several weeks indicates the quasi‐stationary Mei‐Yu in South China and the YRV, respectively. The year‐to‐year variability of the WTs is also evident in the WTs. The El Niño–Southern Oscillation (ENSO) impact on the precipitation in the East Asian region is analysed for three types of ENSO: Eastern Pacific, Central Pacific, and mixed El Niño and La Niña. The seasonal mean precipitation anomalies can be interpreted by the frequencies of the daily WTs under different ENSO conditions. [ABSTRACT FROM AUTHOR]

Considering the unprecedented extremity of the Meiyu episodes in early summer of 2020, here the authors perform a comprehensive study of the intraseasonal evolution characteristics of the observed rainfall round Yangtse as well as the potential modulating effect of Madden‐Julian Oscillation (MJO). Results suggest that the Meiyu rainfall manifests as recurring latitudinal shifts around Yangtse during June–July of 2020, corresponding well to the continued swings of MJO circulation and convection between Phase 1 and Phase 2. The MJO affects the meridional migration of the 2020 Meiyu rainfall mainly through regulating the westward extended ridge line and southwesterly of the anomalous anticyclone over the western North Pacific (WNP). Specifically, the northeastward propagation of boreal summer MJO from Phase 1 to 2 shifts the ridge line of the anomalous WNP anticyclone northeastward. Consequently, the associated southwesterly anomaly over the southeastern China penetrates to the north of Yangtse and enhances the lower‐tropospheric moisture flux convergence, supporting heavy precipitation there. However, when the MJO swings back to Phase 1, the anomalous southwesterly and moisture flux convergence retreat southward, so does the Meiyu rain band. The present results advanced our understanding of the interactions between the latitudinal shifts of extreme Meiyu rainfall episodes and MJO Phase swings. Key Points: The unprecedented extreme rainfall episodes in early‐mid summer of 2020 manifest as recurring latitudinal shifts around Yangtse riverThe north‐south shifts of 2020 Meiyu rainfall show a high correspondence with the recurring Madden‐Julian Oscillation (MJO) Phase 1–2 swingsThe MJO modulates the latitudinal shifts of Meiyu rainfall mainly through changing the westward extended ridge line of western North Pacific anticyclone [ABSTRACT FROM AUTHOR]

New insight into the contribution of anomalous South China Sea (SCS) warming is proposed to understand strong southern China (SC) winter rainfall. El Niño events, which weaken the East Asian winter monsoon (EAWM), favor SC winter rainfall. However, the changes in SC winter rainfall are not always in phase with the El Niño‐Southern Oscillation, making the prediction of East Asian climate challenging. Here, we show that the increased moisture associated with the warming SCS induced by the weakening western boundary current leads to increased meridional moisture transport to SC. Particularly, during the El Niño mature winter phase, this effect works jointly with a weakened EAWM to determine an increased rainfall over SC. Therefore, we suggest that the thermal state of the SCS should be considered when large‐scale tropical ocean‐atmosphere variability is utilized to predict SC winter rainfall. Plain Language Summary: Climate extremes, such as strong southern China (SC) winter rainfall, greatly affect socioeconomic activities and raise great concerns. The South China Sea (SCS) acts as a "portal" to SC and significantly modulates the nonlinear moisture transport to SC. When the SCS is warm enough, the "portal" opens and allows abundant moisture transport toward SC. Particularly during the El Niño mature winter, this effect works jointly with a weakened East Asian winter monsoon to determine increased winter rainfall over SC. Key Points: Tropical air‐sea interaction indices sometimes fail to identify strong southern China (SC) winter rainfallThe role of the South China Sea (SCS) in modulating SC winter rainfall under large‐scale tropical air‐sea interactions is revealedA warmer SCS supports large nonlinear moisture transport from the SCS toward SC, resulting in strong SC winter rainfall [ABSTRACT FROM AUTHOR]

In this study, a new index based on the potential vorticity (PV) framework is proposed for the quantification of the Tibetan Plateau (TP) surface thermodynamic and dynamic forcing. The results show that the derived TP surface PV (SPV) includes the topographical effect, near‐surface absolute vorticity, and land–air potential temperature differences. The climatological annual cycle of the SPV suggests that the TP transitions from a cooling to a heating source in April. The SPV reaches a maximum from June to August, which is consistent with the evolution of the Asian summer monsoon precipitation. Further analysis suggests that the intensified SPV in the boreal summer results in a low‐level cyclonic circulation anomaly associated with increased precipitation over the southeastern slope of the TP and South China and decreased precipitation over the Indian Ocean. In winter, the intensified SPV is associated with local cold air and divergence at the TP surface. Plain Language Summary: The thermal forcing of Tibetan Plateau (TP) has long thought to be important in regulating the Asian summer monsoon. However, the surface sensible heat flux cannot represent the total thermodynamic forcing of the TP because the SSHF decreases when the monsoon precipitation intensifies during the prevailing Asian summer monsoon season. In this study, we propose a new index based on the potential vorticity (PV) framework, which can be used to quantify seasonal and interannual variations in the TP's surface thermodynamic and dynamic forcing. The results show that the proposed index can represent the TP surface‐elevated heating effect during the boreal summer, which is consistent with those of numerical experiments performed in previous studies. The new index can be used as a metric for model evaluation and climate characterization in future studies to quantify the role of the TP in global climate change. Key Points: The Tibetan Plateau surface potential vorticity index (TP‐SPVI) includes the effects from orographic thermal and dynamical forcingThe seasonal variation in the proposed TP‐SPVI is consistent with the time evolution of the Asian summer monsoon precipitationThe surface PV can be used as a metric for the identification of the TP surface forcing in reanalysis data and for model evaluation [ABSTRACT FROM AUTHOR]

Deforestation and intensive land use have accelerated soil erosion, reshaped topography, and altered carbon reservoirs for thousands of years. The timing, scope, and magnitude of long‐term anthropogenic soil erosion across China are especially important to understand the global scale of this process. Here, sediment accumulation rates (SARs) from 191 sediment archives are found to be temporally correlated with monsoon intensity during 6–40 ka BP, indicating that hydroclimate was the main driver of soil erosion in this time interval. The rapid increase in SARs after ca. 5 ka BP is decoupled from persistently weakened hydroclimate but instead follows the trend of increasing population and related agricultural activities in China, implying a change in the primary controlling factor since then. Early human activities in China therefore appear to have had profound implications on Earth's surface at a continental scale. Plain Language Summary: The key agency in modulating Earth's surface environment and carbon reservoirs includes the hydroclimate and anthropogenic factors. However, their effect on the magnitude and drivers of long‐term soil erosion across China is not well understood yet. Here changes in sediment accumulation rates were applied as a proxy for soil erosion. The results showed a direct linkage between soil erosion proxy and Chinese population for ca. 5,000 years, suggesting that hydroclimate controlled soil erosion before the mid‐Holocene, but human impacts overwhelmed afterward and started to control soil erosion ca. 5,000 years ago in China. The timing was about 1,000 years earlier than the global average, highlighting the inter‐continental differences and extending our view of long‐term human‐environment interactions. Key Points: Hydroclimate controlled soil erosion before the mid‐Holocene in ChinaDirect linkages between sediment accumulation rates and Chinese population were detected across ChinaHuman impacts started to control soil erosion in China 5,000 years ago, at least 1,000 years earlier than the global average [ABSTRACT FROM AUTHOR]

The thermal forcing of the Tibet Plateau (TP) causes circulation anomalies that may affect the East Asian monsoon. Hence, summer precipitation in China has a close relation to the previous heat source over TP. The saturation of the atmosphere is the precondition of precipitation, so variations of vapour and temperature adjust the generation of precipitation synergistically. The heating of TP exerts impacts on summer precipitation in China, essentially, through modulating vapour and temperature. The goal of this study is to identify whether the variations of temperature or vapour dominate in the end. Besides, according to the heating characteristics over TP, a more accurate area of spring (March–May) heat source is chosen to indicate the midsummer (July) precipitation in China. The configuration of contributions of temperature and vapour can be divided into two cases. One is that vapour and temperature both increase or decrease, so they play inverse roles. It is easy to find the dominant element in this circumstance. The other is that vapour and temperature have concurrent effects. In this case, their significances need to be further compared. The method based on the linkage of the precipitation and relative humidity is used to quantitatively compare the effects of temperature and vapour. The results are robust and can complement the qualitative analysis with circulations and temperature. In years that there is intense heating on west TP, the Yangtze River basin (YZRB) is controlled by more vapour transport from oceans. The downstream of the Yellow River basin (YLRB) is affected by the dry and cold northerly winds. Dominance analysis shows that vapour general plays a more important role in two major river basins. Maybe not exactly coincide with someone's envision, not all the places are dominated by the vapour. Around northeast China, temperature contributes little more than vapour. [ABSTRACT FROM AUTHOR]

Bias‐corrected monthly precipitation and surface temperature datasets are constructed for the monsoon transitional zone (MTZ) in China during 1965–2100 based on 21 coupled climate models from phase 6 of the Coupled Model Intercomparison Project (CMIP6) using the equi‐ratio and equidistant cumulative distribution function quantile‐based mapping methods (equi‐ratio cumulative distribution function [ERCDF] and equidistant cumulative distribution function [EDCDF]), respectively. The efficiencies of the two methods are verified via cross‐validation by the jack‐knife method, and the biases are remarkably reduced compared to those of the raw model outputs. Then, the bias‐corrected model outputs are applied to future projections of precipitation, surface temperatures and drought events under the medium (SSP2‐4.5) and high (SSP5‐8.5) shared socioeconomic pathway scenarios. The obtained results present pronounced increases in both the projected annual mean precipitation and temperature fields for the model ensemble mean. In accompany, the MTZ is predicted to become drier in the three future periods; this result was attributed to the dramatic increases in semiarid events and to the decreases in humid events. The drought tension showed more rapid development under SSP585 than under the other scenario, with comparable occurrence frequencies of relatively wet and dry events in the long‐term period, posing a serious threat to regional sustainable development. [ABSTRACT FROM AUTHOR]

The author presents an iterative approach to describing a data set, such as a paleoclimatic proxy or a model output, in terms of automata of successively higher order. The automata reflect dynamics acting on successively longer timescales and larger spatial scales. The method uses the computed probability density function from reconstructed state space portraits, over successive overlapping windows in time, of the record of magnetic susceptibility of loess and paleosols at Luochuan, central China. Areas of consistently high probability across several time windows represent areas of metastability, which are used as the predictive and successor states of a succession of Markov Chains that characterize the variability of the strength of the East Asian paleomonsoon at different time scales. Seven metastable states are thus identified, forming four Markov Chains, which show a marked increase in complexity of behavior of the paleomonsoon system throughout the Quaternary. A higher‐order automaton is suggested by the sequence of Markov Chains, suggesting differing cycles of dynamic behavior in the Early and Late Quaternary. Key Points: East Asian paleomonsoon proxy data suggest the monsoon system is multistable, with seven separate multistable "first‐order states"The first‐order states define four distinct modes of operation which have generally increased in complexity over the past 2.2 million yearsHierarchical structure in the dynamics reflects the relative importance of changes driven by insolation and tectonic activity [ABSTRACT FROM AUTHOR]

The East China Sea (ECS) seasonally receives a high organic input due to the terrestrial organic matter influx, which is controlled by the East Asian Summer Monsoon (EASM), and the increased productivity driven by upwelling of the subsurface Kuroshio Current (KC). Changes in benthic foraminiferal assemblage composition in combination with paleoceanographic proxy data (CaCO3 (%), TOC (%), δ13Cpf, and δ18Obf) are used to reconstruct bottom water oxygenation and organic export flux variability over the last 400 kyr in the ECS. Multivariate analyses of benthic foraminiferal census data identified six biofacies characteristic of varying environmental conditions. These results suggest that enhanced EASM precipitation and KC upwelling directly influenced organic export flux and bottom water oxygen content in the ECS. The ECS bottom water was suboxic during Marine Isotope Stage (MIS) 11 to 8; suboxic to dysoxic between MIS 7 and 6, strongly dysoxic between mid‐MIS 5 and 4, and exhibited high variability between MIS 3 and 1. Spectral analysis of relative abundances of representative genera Quinqueloculina (oxic), Bulimina (suboxic), and Globobulimina (dysoxic) reveals a robust 23 kyr signal, which we attribute to precessionally‐paced changes in surface productivity and bottom water oxygenation related to KC variability over the past 400 kyr. Key Points: Four distinct phases of bottom water oxygenation were identified during the last 400 kyr in the East China SeaEast Asian Summer Monsoon and Kuroshio Current influenced East China Sea productivity, organic export flux, and bottom water oxygenationPrecessional variability modulates bottom water oxygenation in ECS [ABSTRACT FROM AUTHOR]

This article explains the Global Energy and Water Cycle Experiment (GEWEX)-Asian Monsoon Experiment (GAME). GEWEX was conducted under the umbrella of the World Climate Research Program and was led by Professor Yasunari from Japan. GAME research focused on water and energy cycles of Eurasia. Intensive field work carried out in eastern Siberia, the Tibetan Plateau, Central China, and Thailand has resulted in new insights into hydrological and meteorological processes. The papers in this issue focus on the hydrological characteristics of the GAME region.

Present knowledge of hydrological changes in the East Asian summer monsoon region during the last deglaciation lacks precision, most especially for central eastern China. A hydrological reconstruction based on elemental ratios, such as Rubidium/Strontium (Rb/Sr) and Zirconium/Rubidium (Zr/Rb), and grain‐size distribution for the period of 22.8–7.4 ka was derived from the Dajiuhu basin in central eastern China. The reconstruction shows that there were some small wet‐dry fluctuations within the basin between 22.8 and 17.5 ka, but an abrupt wetting after 17.5 ka, with a maximum occurring around 15.0 ka, then a drying trend until the early Holocene. This pattern parallels the zonal gradient of sea surface temperature (SST) across the tropical Pacific, which suggests that wet conditions in the Dajiuhu basin respond to the decreased SST zonal gradient. A marked decrease in the tropical Pacific SST zonal gradient, seen as an El Niño‐like state, could lead to an anomalous anticyclonic circulation at the Western Pacific and a southward excursion of the Western Pacific Subtropical High, which favors the occurrence of wet conditions in central eastern China. Meanwhile, this El Niño‐like state could sharpen the SST meridional gradient between the tropics and the extratropics, and then shift the upper tropospheric westerlies southward, which in turn induces a prolonged Mei‐yu and more precipitation in central eastern China. Overall, it is concluded that the El Niño‐Southern Oscillation‐like states might be a major forcing for hydrological changes in central eastern China during the last deglaciation. Key Points: Hydrological reconstruction in the Dajiuhu basin shows an abrupt wet condition from 17.5 to 15.0 ka, then followed by a drying trendOur Dajiuhu records parallel the zonal gradient of sea surface temperature across the tropical Pacific during the last deglaciationEl Niño‐Southern Oscillation‐like states might be responsible for hydrological changes in the Dajiuhu basin during the last deglaciation [ABSTRACT FROM AUTHOR]

Orbital‐scale East Asian Summer Monsoon (EASM) variations inferred from loess deposits in northern China and speleothems from southern China display different dominant periods, complicating our understanding of monsoon response to insolation and ice‐volume forcings. Here we integrate a new microcodium δ18O record from a high‐resolution last interglacial loess profile with previously published data and provide a composite microcodium δ18O record on the Chinese Loess Plateau (CLP) since the last interglacial. The composite microcodium δ18O record displays distinct precessional cycles, consistent with speleothem δ18O records, but with different amplitude contrast (particularly during the peak interglacials). We propose that both loess and speleothem δ18O records exhibit covariations at precessional timescale oscillations. The discrepancy between loess and speleothem from southern China can be attributed to the influences of other processes besides summer precipitation on the proxies. A slight difference in amplitude between microcodium and speleothem δ18O records implies that the EASM is also influenced by inland surface boundary conditions, which has important impacts on the occurrence of EASM precipitation. Therefore, microcodium δ18O from the Chinese loess–paleosol sequences can be regarded as a representative proxy of EASM precipitation in northern China and then a reliable proxy reflecting the variation of EASM intensity. [ABSTRACT FROM AUTHOR]

Wildfire activity is an important activity in evolution of vegetation and carbon cycling. Whether wet weather will suppress wildfire or promote them by increasing fuel reserves during the Holocene is not clear. We obtained a record of black carbon from a sediment core spanning the last 14.8 kyr from Gonghai Lake, in North China. There is a close relationship between the timing of wildfire activity and vegetation development driven by the East Asian summer monsoon intensity. On a millennial timescales, wet climatic conditions provide a sufficient biofuels reserve, in the same period wildfire increase; thus, the regional potential biofuels reserve is shown to be an important controlling of regional wildfire activity in the monsoon region of China, under natural conditions. We infer that with the strengthening of Asian summer monsoon caused by global warming, the wildfire carbon emission in Asian monsoon region may increase in the future. Plain Language Summary: Much attention has been paid to the response of wildfire activity to climate change. Understanding the past history of wildfires and their triggering factors may help us to mitigate the effects of future wildfires. Our study of the black carbon record of the sediments from an alpine lake (Gonghai Lake) in North China indicates that the level of biofuels (mainly woody vegetation) was the main control on the intensity of wildfire on a millennial timescales over the past ∼14,800 yr. When the climate was wetter, more biofuels were available as a result of increased biomass storage, wildfires were more intense with a relatively stable ignition probability. So, climate trends that favor vegetation development will lead to a higher intensity of wildfire and carbon emission in the Asian monsoon region in the future, with the strengthening of Asian summer monsoon caused by global warming. Key Points: The variation of wildfire and summer monsoon is consistent on the millennial scale, wet climate drives wildfire enhancingBiofuels reserve has controlled wildfire for the Holocene in Asian summer monsoon regionStronger monsoons caused by global warming would increase wildfire carbon emission [ABSTRACT FROM AUTHOR]

Much has been learned regarding orbital and millennial timescale climate changes after the onset of Northern Hemisphere glaciations (NHG) at ca. 2.7 Ma. By contrast, little is known about these variations before the NHG due to lack of high‐resolution records. Here we report first millennial resolution quantified East Asian summer monsoon (EASM) precipitation record from the north eastern Tibetan Plateau. The record supports astronomical forcing of EASM during the late Miocene, except for the period of 8.13–8.03 Ma when EASM experienced high amplitude variations at the 100‐, 20‐kyr, and suborbital bands, which is in sharp contrast with the damped astronomical forcing. Detection of strong 100‐kyr and millennial cycles during low eccentricity intervals of the warm late Miocene with ephemeral NH ice sheets cast doubt on NH ice sheet size variations as their exclusive forcing in the late Miocene and late Quaternary paleoclimatic records. Plain Language Summary: Millennial and 100‐kyr cycles in paleoclimate records are normally attributed to Northern Hemisphere ice sheet size variations. Here we present the first 1‐kyr resolution quantitative East Asian summer monsoon precipitation record from the northeastern Tibetan Plateau during the late Miocene, when Northern Hemisphere ice sheets were ephemeral. The record demonstrates strong 100‐kyr and clear millennial cycles. Detection of 100‐kyr and millennial cycles in this warm time interval cast doubt on Northern Hemisphere ice sheet size variations as their exclusive forcing in paleoclimatic records. Key Points: First 1‐kyr resolution quantitative northern China precipitation record during the late MioceneThe record reveals strong 100‐kyr and clear millennial cyclesDetection of 100‐kyr and millennial cycles in this warm interval challenges Northern Hemisphere (NH) ice sheet size variations as their exclusive forcing [ABSTRACT FROM AUTHOR]

The climatic drivers of tropical rainfall and atmospheric circulation in the late Pleistocene are still debated. Some studies suggest that tropical precipitation primarily responded to precession (23–19 ky cycle), whereas others propose that glacial‐interglacial (100 ky) changes in ice sheets and sea level dominate. Here, we reexamine orbital influences on tropical‐to‐subtropical precipitation isotopes using singular spectrum analysis to isolate leading oscillatory modes from proxy records across the Indo‐Pacific Warm Pool (IPWP) and Asian monsoon domain. We find that the IPWP, Bay of Bengal, and South China Sea are dominated by the 100 ky glacial‐interglacial mode of variability, whereas eastern China clearly follows precession, suggesting that precipitation isotopes over the mid‐latitude Asian continent respond to different mechanisms than those in the IPWP or Indian and East Asian monsoon regions. This study demonstrates that glacial cycles, rather than changes in local insolation, are the dominant drivers of Pleistocene IPWP hydroclimate. Plain Language Summary: Reconstructions of past changes in rainfall, derived from cave deposits and ancient leaf waxes, provide an opportunity to understand how the tropical Indo‐Pacific Warm Pool, located between Southeast Asia and Australia, responds to large‐scale changes in global climate. Here, we statistically analyze five long records of rainfall and atmospheric circulation across the Warm Pool, the Indian and East Asian monsoon regions, and eastern China to isolate different external drivers of change between regions for the last 600,000 years. We find that the signal over eastern China is dominated by seasonal changes in solar radiation over mid‐latitudes in the Northern Hemisphere, whereas the signal in the Warm Pool and monsoon regions are dominated by changes in sea level and high latitude ice sheet growth. This clear spatial difference in the external drivers of regional circulation changes suggests that the cave records from China do not exclusively reflect East Asian monsoon rainfall. Additionally, this study supports a strong connection between high and low latitude climates during the last several hundred thousand years. Key Points: Indo‐Pacific precipitation isotopes are dominated by glacial‐interglacial climate shifts for 560 kyPrecipitation isotope records from eastern China are dominated by the 23 and 19 ky precessional cycles for 640 kyIndo‐Pacific climate is linked to high latitude processes, cautioning against assuming local insolation dominates [ABSTRACT FROM AUTHOR]

The traditional paleoclimatological view suggests that monsoonal China was overall wetter when the East Asian summer monsoon (EASM) was strong. However, this view is at odds with the understanding of modern climate, which demonstrates an analogous "tripole precipitation pattern" in monsoonal China. Little is known about the spatial pattern of paleo‐precipitation in monsoonal China, particularly during the past glacial‐interglacial cycles. Here, we provide evidence for a potential tripole precipitation pattern in monsoonal China over the past 425 ka using climate modeling, and compare the results with paleoclimate records available from China. Our simulations illustrate that more (less) precipitation in North China and South China, and less (more) precipitation in the Central‐East China during strong (weak) EASM periods associated with high (low) boreal summer insolation. Our results agree with the present understanding of modern East Asian climate, and furthermore confirm that the boreal summer insolation is the dominant forcing for the intensity of EASM and the response of subtropical high pressures is fundamental in modulating the precipitation pattern in monsoonal China on orbital timescales. This temporal and spatial variability of precipitation, as revealed in our simulations, shows the potential high complexities in hydroclimatic conditions in monsoonal China throughout the past glacial‐interglacial cycles. Nevertheless, whether the tripole precipitation pattern in monsoonal China over the past 425 ka is robust enough still should be tested, preferable by taking advantage of existing and new well‐dated and explicit indicative precipitation archives in Central‐East China. Key Points: Our simulations suggest that the tripolar precipitation pattern in monsoonal China likely occurs on orbital timescalesThe boreal summer insolation is the dominant forcing for the intensity of East Asian summer monsoon on orbital time scalesThis study emphasizes the high complexities in hydroclimatic conditions in monsoonal China throughout the past glacial‐interglacial cycles [ABSTRACT FROM AUTHOR]

The different impacts of El Niño on the East Asian summer precipitation (EASP) between its developing and decaying stages are investigated in observations. The EASP responses are almost opposite between the two stages, with an anomalous wet (dry) in Southeast China and an anomalous dry (wet) in North China in the developing (decaying) summer. In the developing summer, El Niño influence on EASP is through its direct impact of the sea surface temperature (SST) anomaly in the tropical Pacific, which induces heating perturbations that excite an upper‐level zonally propagating wave train in mid‐latitude and a lower‐level meridional wave train along the East Asian coast. In contrast, in the decaying summer, El Niño affects EASP through the El Niño‐generated SST anomalies outside the equatorial Pacific, which are combined to produce an uplift of geopotential height around the upper‐level tropics and a lower‐level Pacific‐Japan (PJ) wave train. [ABSTRACT FROM AUTHOR]

The relationship of the tropical Indo‐Pacific upper ocean heat content (HC) and the South China Sea (SCS) summer monsoon (SCSSM) onset during 1980–2020 was investigated. It was found that when HC anomalies in the preceding winter–spring are positive (negative) in the eastern Indian–western Pacific Ocean or negative (positive) in the southwestern Indian Ocean and eastern Pacific Ocean, SCSSM onset is usually early (late). Empirical orthogonal function (EOF) analysis suggested that the primary EOF modes of HC anomaly in both tropical Pacific and Indian Oceans are associated with El Niño–Southern Oscillation (ENSO). It is through modulating the westerly over the north Indian Ocean–SCS and the western north Pacific subtropical high (WNPSH) via the Walker circulation over the Indo‐Pacific basin, monsoon circulation in the Indian Ocean that the ENSO related Indo‐Pacific HC variation connects with the SCSSM onset. Both the second EOF modes for the tropical Pacific and Indian Ocean also show significant correlations with the SCSSM onset. The former related vertical motion over the SCS–far northwestern Pacific can influence the WNPSH and convection, thus occurrence of the SCSSM. The latter represents the intrinsic Indian Ocean HC variability; the air temperature variation associated with it can modulate the atmospheric circulation in the Indian Ocean–SCS through thermal wind balance, and thus the SCSSM onset by acting on the westerly over the SCS and the WNPSH. A western Pacific index and an Indian Ocean dipole index were defined to represent the leading HC modes in the tropical Pacific and Indian Ocean, respectively. A binary linear regression model was constructed using these two indices to improve SCSSM onset prediction. [ABSTRACT FROM AUTHOR]

We quantitatively distinguish the fast and slow responses of the East Asian summer monsoon (EASM) to aerosol forcing using the outputs from 16 Coupled Model Intercomparison Project Phase 5 (CMIP5) models. The mechanism of the EASM change due to aerosol forcing is then evaluated from the perspective of upper‐tropospheric temperature change. The results show that aerosol forcing leads to the weakening of the EASM circulation and decreases in precipitation. The aerosol‐induced fast atmospheric response dominates the weakening of EASM and the decreased precipitation over the eastern China. In the fast response, upper‐tropospheric cooling in the mid‐latitudes of East Asia during summer changes the circulation structure, thereby causing the weakening of the EASM. The formation of upper‐tropospheric cooling is closely related to the eastward propagation of atmospheric cooling caused by aerosol forcing in Europe and the resulting change in local meridional heat transport. The slow ocean‐mediated response to aerosol forcing partially offsets the weakening of the EASM over the eastern China in the fast response. In the slow response, southwesterly wind is enhanced and precipitation is increased over the eastern China, while southwesterly wind is weakened over the northwestern Pacific and the South China Sea, which dominates the decrease in precipitation over the oceans. The aerosol‐induced changes of land–sea thermal contrasts further confirm that the decrease of upper‐tropospheric land–sea thermal contrasts over East Asia in the fast response plays a key role in driving the weakening of the EASM. [ABSTRACT FROM AUTHOR]

We reconstruct the incision history of bedrock rivers based on inverse modeling of the long profile of a river channel and the low‐temperature thermochronological data. Our approach first infers an erodibility‐dependent incision history through a linear inversion of the channel elevations of the river. Then to calibrate the reconstructed incision history in the geological timescale, we constrain the erosional efficiency by optimizing the erosion process of the river catchment using a Bayesian analysis, such that the exhumation and cooling paths of bedrocks in the catchment conform to the observed thermochronological ages. We apply this approach to estimate the incision history of the Three Gorges, Yangtze River in East Asia. We modeled the incision histories of three tributaries on the mainstem Yangtze River near the eastern end of the Three Gorges area, assuming that the gorge incision was driven by increased upstream drainage area of the Upper Yangtze (Scenario 1) or local tectonic uplift (Scenario 2). The results of both scenarios suggest an early Miocene onset of the incision of Three Gorges, that is, 18 ± 6 Ma or 21 ± 4 Ma, respectively. During the Pliocene, our models suggest a significant decrease in the gorge incision rate. By comparing the estimated gorge incision history to the late Cenozoic denudation of the eastern Tibetan Plateau and the regional climate change, we suggest that the incision of the Three Gorges has been heavily affected by the development of the Upper Yangtze River and the East Asian monsoon. Key Points: River incision history is modeled using topographic and published (U‐Th)/He dataInversion of the data suggests accelerated incision rate since the early MioceneGorge incision rate decreased during the Pliocene due to the declined monsoonal rainfall [ABSTRACT FROM AUTHOR]

A regional Climate‐Weather Research and Forecasting (CWRF) model with a 30‐km horizontal resolution was applied to simulate the East Asian summer monsoon (EASM) and climate in China from 1980 to 2016. As compared with observations and reanalysis data, the model can reasonably reproduce the spatial distributions of the climatological mean atmospheric circulation and water vapour transport in East Asia, as well as the seasonal advance and retreat of EASM and rain bands. The correlation coefficient between the EASM circulation index in the simulation and reanalysis is.97. The model can well represent the geographic distributions of summer mean temperature and precipitation over most of China. However, model biases still exist, in particular the skill in the Yangtze–Huaihe River basin is relatively low. The simulated climatological mean temperature and precipitation deviations from observations may be related to the model's systematic circulation biases, with a thicker lower troposphere (i.e., higher temperature between 500 and 1,000 hPa) over most of China (except for the south and southwest) and a thinner one over the coastal oceans in summertime. Compared with the reanalysis, the model overestimates the land‐ocean thermal contrast, which causes the South Asian High shifted to the north and east, as well as the subtropical high and tropical convective activity located further north and persisted longer. Consequently, more water vapour transports northward, leading to more precipitation over North China–Northeast China and less precipitation over the Yangtze and Huaihe River basin. Therefore, the enhanced land‐ocean thermal contrast may be a major factor for the stronger EASM in the model, and corresponding precipitation and temperature biases in China. This analysis provides important information for further improving model performance in EASM simulation. [ABSTRACT FROM AUTHOR]

Here we present, to date, the highest‐resolved (~5 years) and most precisely dated Holocene monsoon climate reconstruction for the western Chinese Loess Plateau based on five replicated stalagmite δ18O records from Wuya Cave, eastern Gansu, China. Our record suggests the wettest period occurred between 10,500 and 6,600 a BP in this region. After this period, the amplitude of Asian summer monsoon decadal‐scale variability progressively increased likely in response to increasing ENSO frequency since the middle Holocene. Our study reveals similar asymmetric centennial‐scale double‐plunging structures of the 8.2, 5.5, and 2.8 ka events in the western Chinese Loess Plateau, suggesting a possible role of solar activity whose impact was amplified around 8.2 ka BP by the meltwater flood. In contrast, the 4.2 ka event exhibit gradually declining monsoon rainfall with centennial‐ to decadal‐scale fluctuations. Key Points: A 5 year‐resolved Holocene Asian summer monsoon record was reconstructed for the western Loess Plateau based on speleothemsThe wettest period occurred between 10,500 and 6,600 a BP, after that, the amplitude of decadal‐scale monsoon variability increasedSimilar structures were observed during the 8.2, 5.5, and 2.8 ka weak monsoon events, which are different from the 4.2 ka event [ABSTRACT FROM AUTHOR]

How and to what extent are human societies affected by climate change? There has been a growing body of research using big historical data and statistical analyses to provide scientific answers to this inter‐disciplinary research question. However, quantitative analysis measuring the historical demographic impact of ocean/atmosphere interaction is still scanty. Here we use 544 years (1368–1911) of historical records to trace the demographic impact brought about by ocean/atmosphere interaction in Shaanxi, located on the northern fringe of the Asian summer monsoon region in China. Our results show that: (1) North Atlantic Oscillation (NAO) and El Niño Southern Oscillation (ENSO) caused Malthusian catastrophes mainly through drought at the inter‐annual scale; (2) drought reinforced the synchrony of various Malthusian catastrophes at the inter‐annual to multi‐decadal scale; and (3) the unusual cycles of NAO drove drought and various Malthusian catastrophes in the cold 1550–1730 period at the multi‐decadal scale. This study represents a pioneering attempt to quantitatively assess the demographic impact caused by the ocean/atmosphere in historical China. Our findings may help to conceptualise the climate–human nexus in those ecologically marginal regions that are impacted by ocean/atmosphere interaction, and to explain the synchrony of social crisis in Eurasia in the 17th century. [ABSTRACT FROM AUTHOR]