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Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The periodicities of the climate change have long been explored by researchers not only because they reflect the inherent characteristics of the climate systems, but also because they are the foundations of climate-change predictability. This paper reports the periodicities of the hydroclimate variations reconstructed from a lacustrine sequence at Tiancun section (TC section) in the Luoyang Basin within the Central Plains of China and the sequence covers the first half of the Holocene. Our reconstruction shows that the hydroclimate variations at the TC section during the period from ∼10,135 and ∼ 5890 cal. yr BP were well corresponding with the effective soil moisture variations recorded by the stalagmite δ13C sequence at the Magou Cave. This corresponding relationship suggests that when the effective soil moisture increases (i.e., more negative δ13C values), the ratio of evaporation over precipitation in the paleolake at the TC section decreased, resulting in lower CaCO 3 content. It also suggests that when the effective soil moisture increases, more inflowing water entered the paleolake, resulting in coarser sediments. Our reconstruction also shows that the hydroclimate variations or lake level variations in the Luoyang Basin were characterized by millennial-scale quasi-periodicities that were most likely paced by the changes in ITCZ (Inter-tropical Convergent Zone) position and also by alterations in ENSO-like phase. And, both (ITCZ and ENSO) were most likely regulated by the solar activity. Our further analysis shows that the hydroclimate in the Luoyang Basin also experienced centennial-scale variations. Specifically, the grain size data express the following cycles: 692-year, 538-year, 217-year, 170-year and 123-year, all at the 99% confidence level. And, the CaCO 3 content data express the following cycles: 202-year, 184-year, 169-year and 85-year, all at the 99% confidence level. These cycles are approximately coincident with the widely-reported solar-activity cycles. • This paper reports the periodicities of the hydroclimate variations reconstructed from a lacustrine sequence in the Central Plains of China and the sequence covers the first half of the Holocene. • The hydroclimate variations were primarily paced by changes in ITCZ position and also by alterations in ENSO-like phase. And, both (ITCZ and ENSO) were most likely regulated by solar activity. • The centennial-scale hydroclimate variations were approximately coincident with the widely-reported solar-activity cycles. [ABSTRACT FROM AUTHOR]

Three major points of population migration toward the WHL occurred at 5200, 3800, and 2800 cal BP, which correspond to the seesaw changes of precipitation in western and eastern China. [Display omitted] How various peoples crossed geographical barriers, were affected by climate change and human-made technologies comprise some of the most interesting quandaries in the history of cultures. This paper considers the Hu line, which is a major boundary between population centres and different environments in China. The boundary became evident approximately 11,400 years ago; however, evidence suggests that people crossed through at 5200, 3800, and 2800 cal a BP, facilitating the increases of the trans-Eurasian exchange. The timings of the crossings correspond to the weakening of the East Asian summer monsoon that triggers seesaw changes of precipitation in western and eastern China. This analysis demonstrates that climate change on a millennial-to-centennial scale can have a profound influence on population distribution with long-term consequences. [ABSTRACT FROM AUTHOR]

Speleothem δ13C in monsoonal China differs from speleothem δ18O, which is widely used as a climatic proxy for several complex control reasons. Nevertheless, δ13C records have the potential to reveal the implications of hydroclimatic changes. This study reports a speleothem δ13C record from Didonghe (DDH) Cave in central China spanning 34 to 13 kyr BP. After we investigated the factors that influence speleothem δ13C, we found that the δ13C record showed that DDH Cave can prompt directional shifts via local hydroclimatic changes, such as in vegetation types, biomass, and rock–water interaction processes, suggesting that δ13C is mainly controlled by the local hydroclimate. Ensemble empirical mode decomposition (EEMD) results revealed a coupling relationship between δ18O and δ13C on multiple timescales, which suggested that changes in precipitation caused by large-scale monsoonal circulation are controlled by regional hydrological conditions to a great extent. However, the hydrological conditions of the cave were relatively mild and humid during the last glacial maximum (LGM), which revealed the impact of evaporation on changes in the region's hydrological conditions. We also found that the δ18O and δ13C profiles decoupled when δ13C changed with a shift in the location of the westerly during HS1. The δ13C record correlates well with other paleoclimate records, suggesting that regional hydrological conditions are also modulated by the Earth's internal and external driving factors. [ABSTRACT FROM AUTHOR]

The Heinrich Stadial 2 (HS2) event is poorly defined in the Greenland δ18O ice core record; however, it can be identified in stalagmite records from China. In this paper, we reconstruct an absolutely-dated and high-resolution calcite δ18O record from Shima Cave, central China, covering the interval from 26.0 to 23.9 ka BP, with a temporal resolution of ~16 years. By integrating our newly reported record with all available δ18O records of Marine Isotope Stage 2 from China, which are securely 230Th/U-dated, we calculate the timing of the onset, termination and duration of HS2. The statistical results show that the prominent HS2a phase started at ~24.4 ± 0.1 ka BP and ended at ~23.6 ± 0.1 ka BP, lasting approximately 0.8 ± 0.3 ka. If the onset of the Dansgaard-Oeschger 2 event in the Greenland δ18O record is synchronous with the termination of HS2a, then the GICC05 chronology should be adjusted by +230 years to align it with stalagmite results. Further investigation of HS2 shows that Chinese cave records exhibit a distinct two-fold structure, corresponding to HS2a and HS2b, as observed in marine sediment cores, particularly those recovered around the Atlantic Ocean. These records show comparable changes in relative amplitudes during the HS2a and HS2b phases, which could possibly be related to different weakening episodes in the Atlantic Meridional Overturning Circulation. • An ~16-year-resolution East Asian summer monsoon (EASM) history covering the onset of Heinrich Stadial 2 event. • Statistical analyses of timing for Heinrich Stadial 2. • Globally pervasive twofold structure during Heinrich Stadial 2. [ABSTRACT FROM AUTHOR]

The driving force of climate change in the monsoon margin is complex, making it a key area for regional and global climate change research. Palaeohydrological studies in the monsoon margin have increased the resolution of research in the long term, transitioning from qualitative to quantitative studies to comprehend climate change processes, patterns, and mechanisms. Testate amoebae (TA) in peat sediments are used as a proxy indicator organism for quantitative reconstruction of palaeohydrology. Thus, their community changes are directly related to precipitation, and widely used to reconstruct the patterns of summer precipitation globally. We investigated TA species and reconstructed palaeohydrological changes in the Greater Khingan Mountains' Hongtu (HT) peatland, located in the East Asian Summer Monsoon (EASM) margin. The result showed that the most abundant TA species were Assulina muscorum (12.4 ± 5.0%) and Nebela tincta (8.9 ± 4.9%) in the HT peat core. The increase in dry indicator species (e.g., A. muscorum and Alabasta militaris) indicated a drying pattern in the HT peatland since 150 cal yr BP. Principal component analysis (PCA) explained 47.6% of the variation in the selected TA assemblages. During 400 to 250 cal yr BP, PCA axis 1 scores ranged from 0.2 to −1.3 (reflecting a drier climate), associating with the Little Ice Age. The paleohydrology of the northern part of the Greater Khingan Mountains was mainly controlled by the EASM, which was associated with changes in North Atlantic Sea surface temperature and solar radiative forcing. The apparent drying pattern may be the result of the gradual intensification of anthropogenic activities and the increase in EASM intensity. [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon brings a large amount of precipitation in East China every year, which is the main source of water resources for China. At the same time, it often causes the severe flooding disasters. The Chinese meteorologists and hydrologists have realized that the moisture transport intensity, the extent and persistence of summer monsoon may play a crucial role in extreme rainstorm processes. This branch of moisture transport belt may be termed as the East Asian summer monsoon moisture transport belt. It can be categorized in the atmospheric river (AR) coined internationally, but it is not a fully same conception, due to its unique regional feature of the East Asian summer monsoon. The monsoon moisture transport belt is a main producer of excessively heavy rainfalls and disastrous floods in this region. Based on the data of the past hundred years, this paper made an update re view of the characteristics and formation reasons of the East Asian summer monsoon moisture transport belt. Taking the five strongest continuous heavy rain processes in the Haihe River, Yellow River, Huaihe River and Yangtze River in the past hundred years as examples, the important role of the monsoonal moisture transport belt is analyzed. Finally, it is proposed that climate warming can affect the global water cycle through four aspects, including holding more water vapor in the atmosphere, changes of the atmospheric circulations and radiation forcing with climate warming as well as the regional impact of aerosols. [ABSTRACT FROM AUTHOR]

As a consequence of global warming, extreme weather events are becoming more prevalent, which influences socioeconomic development. It is vital to reveal the variations of regional extreme precipitation for flood prevention and mitigation. This research presents a comprehensive analysis of spatiotemporal variation and segmentation trend of extreme precipitation indices (EPIs) from the spectrum of intensity, frequency, and duration in the Lixia River Basin (LRB), China, from 1960 to 2019. The influence of global warming [global mean near-surface temperature (GSTEMP)], atmospheric circulation [e.g., multivariate ENSO index (MEI), and East Asian summer monsoon index (EASMI)], and local effects (e.g., relative humidity and local temperature) are examined to explore the dominant driving factors on the trend of EPIs. Results show that the intensity and frequency of EPIs increase across the LRB, whereas the durations of extreme precipitation are decreasing. And the lower reach has more frequent extreme precipitation than the upper reach. And most stations in segmentation trend analysis of EPIs show UUD (i.e., increasing from 1960 to 1980, increasing from 1981 to 2000, and decreasing from 2001 to 2019). What is more, the intensity and frequency of extreme precipitation are more actively related to local temperature and relative humidity than others, with local temperature being the primary negative impact while other factors are positive. And relative humidity and GSTEMP have a greater impact on the duration of EPIs than others. The findings will help figure out how regional global warming affect the trends of extreme precipitation, and can be used on a regional scale for the development of socioeconomic activities. [ABSTRACT FROM AUTHOR]

The Maritime Continent (MC) is an important region where the Tropical Pacific and the Indian Ocean interact with each other via "the atmospheric bridge" and a key region for the interaction between the Asian and Australian monsoons. Using the NCEP/NCAR and CMAP monthly mean reanalysis over the period of 1979-2012, the interdecadal variations of diabatic forcing over the key region of the Maritime Continent and its possible relations with the East Asian summer monsoon have been investigated in the present paper. Our results show that climate variations in the Maritime Continent is particularly significant in the area of95-145°E, l0°S-10°N, which is thus defined as the key area of the MC (i.e., KMC area). Without the input of latent heat release in the atmosphere, distinct interdecadal change of diabatic heating is found to exist from 1979 to 2012; it intensified before 1980s and peaked in the late 1980s and weakened after this period. By analyzing each individual component that contributes to the diabatic heating in the KMC area, surface latent heat flux and net long-wave radiation in the atmosphere are found to be the two dominant components. With negative diabatic heating anomalies over KMC, there will be more precipitation on islands and less precipitation over sea, and more rainfall around the equator, which is in correspondence with the convergence center around the equator in the KMC area . Along the meridional-vertical section averaged between 115-1 20°E, the well-defined vertical circulation anomalies are observed with the ascending branches over KMC and the area around 30°N respectively, and the descending branch over the South China Sea. Water vapor transports from the Bay of Bengal and South China Sea to eastern China to benefit the positive precipitation anomalies. The meridional-vertical circulation in East Asia plays a critical role in linking the interdecadal variability of diabatic heating over the KMC and East Asian summer monsoon anomalies. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Year-to-year variations of summer precipitation over the densely populated central China can exert great impacts on the local society and economy. Using the observed and reanalyzed datasets for the period 1960–2020, this study investigates the relationship between the decaying El Niño and the central China summer precipitation (CCSP). The results show that the central China tends to feature excessive precipitation during post-El Niño summers. In particular, we find that such a climatic effect of El Niño exhibits an evident interdecadal strengthening since the early 1990s. This is due to the changing intensity and duration of the El Niño events. Compared to the prior decades (1960–1992), there are stronger intensity and longer duration of the El Niño-related warm sea surface temperature (SST) anomalies in the tropical central Pacific in the epoch after the early 1990s (1993–2020). Through the Walker circulation adjustment, the strengthened intensity and longer duration of the central Pacific SST anomalies cause stronger and longer-lasting easterly anomalies along the equatorial Indian Ocean, which can further intensify the SST warming over the Southwest Indian Ocean (SWIO) in boreal spring following El Niño by forcing a downwelling Rossby wave. The robust SWIO warming induces stronger Indian Ocean basin-wide SST warming and anomalous anticyclone over the Northwest Pacific in post-El Niño summers through initiating a series of ocean-atmospheric interactions. As a result, the anomalous anticyclone would deliver the abundant water vapor to the central China and contribute to increased local summer precipitation. By contrast, in the prior epoch (1960–1992), the El Niño-related SST warming in the central Pacific is relatively weaker and shorter-lasting, which results in weaker Indo-Pacific climate interactions in the decaying summer, thus having no significant impact on the CCSP. Our results highlight a strengthening influence of El Niño on the following summer precipitation over the central China since the early 1990s. This has important implications for the regional seasonal climate prediction. [ABSTRACT FROM AUTHOR]

The central China summer precipitation (CCSP) is of great importance to the people's livelihood of this densely populated region, including the agriculture, ecosystems, water resources, economies, and health. Based on the observed precipitation, sea surface temperature (SST), and atmospheric reanalysis datasets, the present study investigates the effects of El Niño in the developing stage on the CCSP during 1960–2014. The results show that the CCSP anomalies exhibit significant negative correlations with the El Niño-related SST anomalies in both the simultaneous summer and the following winter, implying that the developing El Niño is important for modulating the CCSP. However, this climatic teleconnection of El Niño is unstable, with an obvious interdecadal change around the late 1980s. Specifically, the negative correlation is not statistically significant in the previous epoch before the late 1980s (1960–1988), but dramatically strengthens since the late 1980s (the post epoch for 1989–2014). Such an interdecadal change is closely associated with the change of the El Niño-related SST anomaly pattern. Compared to the previous epoch, the central Pacific El Niño occurs more frequently in the post epoch, leading to an interdecadal shift of the maximum warm SST anomalies from the eastern Pacific to the central Pacific. The resultant westward extension of the atmospheric circulation responses induces an anomalous low-level cyclone covering South China in the post epoch. It would prevent the southwest monsoon from delivering the moisture to the north and hence reduce the CCSP. While, in the previous epoch, the anomalous cyclone locates east of South China, exerting insignificant influence on the CCSP. This work highlights a strengthening effect of El Niño on the CCSP since the late 1980s, with great implications for the regional seasonal climate prediction. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Extreme precipitation can have catastrophic effects in China by triggering floods, landslides, and other natural disasters. We measure extreme precipitation over eastern China by the maximum of five-day precipitation amount (Rx5day) in June, July, and August (JJA), which contributes more than 20% of the climate mean of JJA regional total precipitation. Based on the empirical orthogonal teleconnection (EOT) method, this work identifies four dominant regions of observed Rx5day interannual variability in eastern China: north-eastern China (EOT1), the southern lower reaches of the Yangtze valley (EOT2), southern China (EOT3) and the northern lower reaches of the Yangtze valley (EOT4). EOT1 extreme precipitation is related to a strong East Asian Summer Monsoon (EASM), a weak monsoon front and a northward displaced upper-tropospheric westerly jet. EOT2 and EOT4 extreme precipitation are related to an enhanced and stable monsoon front and a strong western North Pacific subtropical high (WNPSH). The WNPSH associated with EOT4 is stronger than that associated with EOT2, which pushes the monsoon front further north. EOT3 represents extreme precipitation that is related to anomalous southerlies around the western ridge of the WNPSH. The southerlies transport warm and moist air to southern China and increase precipitation there. The four key regions and the related mechanisms are not sensitive to the EOT technique, as the EOT-based extreme precipitation patterns and circulation anomalies are confirmed using Self-Organising Maps (SOMs). [ABSTRACT FROM AUTHOR]

The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3. The results show that anomalous SST warming in the Kuroshio Extension in winter causes the enhancement and northward movement of the EASM. The monsoon indexes for East Asian summer monsoon and land-sea thermal difference, which characterize the intensity of the EASM, show an obvious increase during the onset period of the EASM. Moreover, the land-sea thermal difference is more sensitive to warmer SST. Low-level southwesterly monsoon is clearly strengthened meanwhile westerly flows north (south) of the subtropical westerly jet axis are strengthened (weakened) in northern China, South China Sea, and the Western Pacific Ocean to the east of the Philippines. While there is an obvious decrease in precipitation over the Japanese archipelago and adjacent oceans and over the area from the south of the Yangtze River in eastern China to the Qinling Mountains in southern China, precipitation increases notably in northern China, the South China Sea, the East China Sea, the Yellow Sea, and the Western Pacific to the east of the Philippines. North China is the key area where the response of the EASM to the SST anomalous warming in the Kuroshio Extension is prominent. The surface air temperature shows a warming trend. The warming in the entire troposphere between 30°N and 50°N increases the land-sea thermal contrast, which plays an important role in the enhancement of the EASM. Atmospheric circulation and precipitation anomalies in China and its adjacent regions have a close relationship with the enhancement of the Western Pacific subtropical high and its northward extension. [ABSTRACT FROM AUTHOR]

Lake level and its inferred East Asian summer monsoon (EASM) evolution in northern boundary of EASM during the Holocene are highly debated. Here, we present a 15-ka record of glycerol dialkyl glycerol tetraethers (GDGTs) in a closed lake in northern China to address this issue. Surface and downcore sediment data demonstrate sedimentary GDGT-0 and branched GDGTs (brGDGTs) are of aquatic production. Contents of GDGT-0 and brGDGTs increase but brGDGT-based paleo-temperature proxy decreases with water depth in surface sediments along a nearshore to offshore transect. This trend is likely due to an increasingly hypoxic condition, favored by anaerobic microbes producing these GDGT-0 and brGDGTs, in bottom water. Accordingly, brGDGT-derived water temperature and pH would reflect bottom water conditions that are largely regulated by water depth of the lake. Downcore GDGT data and their derived temperature and pH consistently reveal a gradually increasing lake level from the late Pleistocene to the early Holocene, a high level during 9.5–5 ka BP and a decreasing trend afterward. The lake-level records from independent and robust proxies in this study largely agree with pollen records in the region, supporting a mid-Holocene maximum EASM precipitation. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Instrumental data indicate the occurrence of a dipolar pattern of precipitation anomalies between north China and the Yangtze River Valley (YRV), which was termed "northern drought (flood)—southern flood (drought)" scenario. It has been shown that this pattern occurred during the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). However, there are questions about whether this dipolar pattern also occurred during the entire Holocene, and the mechanism responsible. Addressing these questions is of fundamental importance for understanding the spatiotemporal evolution of precipitation in East Asian summer monsoon region. Numerous studies of north China have demonstrated that the mid‐Holocene was humid, and the early and late Holocene were dry. However, there are relatively few equivalent studies in the YRV. To this end, we conducted detailed geochemical analysis of an AMS 14C‐dated sediment core from Lake Nanyi in the YRV. Our results indicate humid periods at Lake Nanyi occurred during 11.5–8.0 ka and from 2.0 ka to the present, while dry conditions occurred during ~8.0–2.0 ka. These results, together with published records from Dajiuhu peatland and Heshang Cave, collectively indicate in the YRV, the mid‐Holocene (~8.0–3.0 ka) was dry, while the early and late Holocene were humid, which is the inverse of the pattern in north China. Thus, we conclude there was an asynchronous evolution of hydroclimatic changes between north China and the YRV during the Holocene. We interpret this dipolar pattern as the result of ENSO variations: in a La Niña‐like state, the Western Pacific Subtropical High retreated northeastward, which would enable the rainfall belt to move northward and result in increased (decreased) precipitation in north China (the YRV). Sea surface temperature records from the Pacific Ocean and model simulations support this mechanism: a La Niña‐like state in the mid‐Holocene resulted in more (less) precipitation in north China (the YRV). [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]

Ecological responses to past climate change as determined from palaeorecords offer insights into responses that may accompany future climate change. In arid and semi‐arid lands, the interactions between regional vegetation and climate change are not yet well understood, partly due to a lack of suitable palaeovegetation proxies that can provide accurate and continuous tracers for past vegetation dynamics. To gain a better understanding of long‐term vegetation dynamics, this study employs a multiproxy approach applied to sand‐palaeosol sediments of northeastern China's Songnen grasslands. Phytolith analyses and data on the stable carbon isotope composition (δ13C) of organic matter are used to reconstruct palaeovegetation composition, namely, the changing abundance of C3 and C4 species, whereas a geochemical weathering index (Fed/Fet ratios) tracks past East Asian summer monsoon (EASM) intensity. The phytolith assemblages and indices and δ13C of the soil indicate that C4 species' abundance has been increasing in the Songnen grasslands since the mid‐Holocene, although C3 vegetation is still dominant. Statistically significant negative correlations between the δ13C data and Fet/Fed ratios suggest that continuous weakening of the EASM since the mid‐Holocene may be responsible for the 13C‐enrichment of the sediments in the Songnen grasslands. Field vegetation surveys, modern topsoil phytoliths and δ13C calibration data indicate that the expansion of C4 species since the mid‐Holocene is mainly due to their ability to cope with aridity when growing season temperature is not undergoing a significant decrease. Future precipitation decreases in arid and semi‐arid lands should make C4 species more competitive in the grasslands of northeastern China. HighlightsA continuous grassland landscape history is reconstructed from a sand‐palaeosol sequence via phytolith analysis.Multiple independent approaches were used to reconstruct past EASM intensity and palaeovegetation patterns.Phytolith and δ13C analyses indicate an increase in C4 species since the mid‐Holocene.Aridification drives the increase in C4 species within the grassland ecosystem. [ABSTRACT FROM AUTHOR]

We implemented a subgrid terrain radiative forcing (STRF) scheme into the International Centre for Theoretical Physics, Italy, Regional Climate Model Version 4.1 (RegCM4.1) and evaluated its impacts on the summer precipitation simulation over China by comparing the model results from the experiments with and without the STRF scheme. The RegCM4.1 without the STRF scheme simulates strong East Asian summer monsoon and overestimates the summer precipitation over China. Adopting the STRF scheme in the RegCM4.1 improves the representation of surface radiation process over complex terrains, by reducing the net gain of the surface radiation energy over the Tibetan Plateau (TP). As a result, the heat released from the surface to the overlying air column decreases, thus suppressing the development of local convection over the TP. In addition, the weakened TP thermal forcing due to the STRF effect reduces the land‐sea thermal contrast, resulting in a weakened East Asian summer monsoon that produces less transport of water vapor from tropical oceans and hence weakens summer precipitation over China. Our analysis indicates that such improvement in the precipitation simulation induced by the STRF effect is mainly due to the improved simulation of precipitation intensity, particularly that associated with the moderate and heavy precipitation events, and convective processes. Key Points: A subgrid terrain radiative forcing (STRF) scheme was developedRegCM4.1 model with considering the STRF effect improved the summer precipitation simulation over China [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon (EASM) and the Australian winter monsoon (AWM) are two important components of the Asian-Australian monsoon system during boreal summer. The simultaneous variations of these two monsoons would have remarkable impacts on climate in the Asian-Australian region. Using the reanalysis datasets, we investigated the mechanisms of variation and impacts of East Asian-Australian monsoons (EAAMs). The singular value decomposition (SVD) is performed of the June-July-August (JJA) mean anomalous zonal wind for AWM as the left field and JJA mean anomalous meridional wind for EASM as the right field after both El Niño-Southern Oscillation and India Ocean Dipole signals are filtered out. Our results demonstrate that AWM and EASM are closely related to each other as revealed by the first leading SVD mode. The anomalously strong (weak) EAAMs correspond to anomalously strong (weak) AWM and EASM to the south of 30°N. When EAAMs are anomalously strong, cold sea surface temperature anomaly (SSTA) appears in regions near northern and northeastern coasts of Australia, whereas the warmer SSTA appears in the northwestern tropical Pacific and South China Sea. The colder SSTA is associated with the upwelling of cold water from below, induced by equatorial easterly anomalies, reinforcing the anticyclonic circulation over Australia through the Matsuno/Gill-type response, whereas warm SSTA appears in the northwestern tropical Pacific and South China Sea as a result of oceanic response to the intensified northwest Pacific subtropical anticyclonic circulation. The EASM couples with AWM via the anomalous easterlies near the equator in the Maritime Continent (MC) region and the slanted vertical anomalous circulations. In the years with strong EAAMs, precipitation decreases in northern Australia and over areas from the western Pacific to Bohai Sea and Yellow Sea of China. Meanwhile, the western MC and the southeastern China experience more-than-normal precipitation. [ABSTRACT FROM AUTHOR]

The effects of spring soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China (YRNC) and El Niño on the East Asian summer monsoon (EASM) and precipitation in eastern China, as well as the relevant mechanisms, are investigated using the modified atmospheric model ECHAM5 coupled with the Common Land Model. These models are the atmospheric and land components of the climate system model developed at the Chinese Academy of Meteorological Sciences (CAMS-CSM). The simulations show that both soil moisture anomalies in eastern China and El Niño sea surface temperature (SST) anomalies have significant influences on the EASM, with the effect of soil moisture being slightly greater than that of the El Niño. However, the impacts of soil moisture on EASM and rainfall in eastern China are markedly different from those of the El Niño. Wetter (drier) soil over the YRNC corresponds to less (more) precipitation over northern and southeastern China, and more (less) precipitation over the Yangtze River basin and northeastern China, as well as a strengthened (weakened) and westward-shifted (eastward-shifted) West Pacific Subtropical High and a deepened (shallower) East Asian trough, representing a weakened (strengthened) EASM pattern. During El Niño developing summers, an anomalous anticyclone extends from northeastern to northern China, and an anomalous cyclone occupies the middle and lower reaches of the Yangtze River and southern China. Concurrently, the West Pacific Subtropical High is anomalously weaker than normal. As a result, rainfall anomalously increases over the lower reaches of the Yangtze River and southern China, and decreases over northern and northeastern China. In El Niño decaying summers, there is an anomalous cyclone over northeastern China and an anomalous anticyclone over southern China. The convergence of southerly airflow and northerly winds leads to enhanced rainfall around northern China and the middle reaches of the Yangtze River, and reduced rainfall over other regions. [ABSTRACT FROM AUTHOR]

Projecting regional rainfall changes in a warmer climate attracts ongoing attention. However, large uncertainty still exists in multi-model projection. In this study, we introduce a bias-corrected method to correct the multi-model projection of changes in East Asian summer monsoon (EASM) rainfall based on the historical and RCP8.5 runs of 25 models from phase 5 of Coupled Model Intercomparison Project. Firstly, the total rainfall changes are separated into the thermodynamic component due to increased specific humidity and the dynamic component due to circulation changes. The thermodynamic component is corrected using the observed present-day rainfall and the increase rate of specific humidity based on the wet-get-wetter mechanism. On the other hand, the dynamic component with the circulation changes is corrected based on a "spatial emergent constraint" method, which is further validated by the perfect model approach. Together, these corrections give an integrated projection for EASM rainfall changes under global warming. Such an approach can improve the signal-to-noise ratio of projection effectively, from the original 0.73 of the multimodel mean to around 1.9. The corrected projection of EASM rainfall changes shows a pronounced increase in southern China, the northwest Pacific and a belt from northern China to northeastern China, and a weak increase in other EASM regions. [ABSTRACT FROM AUTHOR]

The South Asian high (SAH) and the North Pacific subtropical high (NPSH) are two crucial systems affecting the summer rainfall over East Asia. Features of the relative vorticity of the SAH and its dynamic effect on zonal extension of the western NPSH (WNPSH) are investigated on interannual timescales using data diagnosis and numerical model experiments. Results show that two climatological centres of negative relative vorticity are observed along the northern flank of the SAH over the Tibetan Plateau and northern West Asia at 200 hPa during boreal summer. The relatively more intense centre over the Tibetan Plateau (TPV) shows a pronounced southeast‐northwest (SE‐NW) variation, indicating a SE‐NW shift of the SAH. When the SAH shifts southeastward, an anomalous anticyclone occurs over eastern China at 200 hPa. In the middle troposphere, this anomalous anticyclone is located over southern China and the northern South China Sea, leading to a westward extension of the WNPSH. A diagnostic analysis of the vorticity equation indicates that the negative relative vorticity anomalies at 500 hPa are mainly caused by the downward advection of the mean relative vorticity by anomalous sinking motions. When the SAH extends southeastward, intense convergence on the southeastern flank of the anomalous upper‐level anticyclone induces descending motions that cause downward advection of mean negative vorticity. Consequently, negative vorticity anomaly is formed at 500 hPa, leading to a westward extension of the WNPSH. Results from the experiments using an idealized anomalous atmospheric general circulation model further demonstrate that the upper‐level anomalous anticyclone associated with a southeastward extension of the SAH triggers an anomalous anticyclone at the middle level, causing a westward extension of the WNPSH. [ABSTRACT FROM AUTHOR]

As a unique continental archive, speleothem has been widely used in reconstructing paleoclimate change. However, the interpretation of Chinese speleothems δ18O has remained a subject of debate. Recently, a Community Atmosphere Model version 3 (CAM3) study indicated that the stalagmite δ18O from eastern China reflected the Indian summer monsoon (ISM) intensity rather than the East Asian summer monsoon (EASM) intensity during Heinrich events. Here, we present a high-resolution speleothem δ18O record from Xianglong Cave in Shaanxi province, China, covering the period of 25.5–10.9 ka BP. The XL15 record shows similar variations with ice core record from Greenland and other climate records from China and India on millennial scale, including Heinrich 2 (H2), Heinrich 1 (H1), Bølling–Allerød (BA) and Younger Dryas (YD) events, supporting the connection between the Asian monsoon and northern high latitude climate. The δ18O amplitude of our record is larger than or similar to the stalagmite δ18O records from India during these events. In addition, differences of stalagmite δ18O in eastern China and the ISM region were observed on glacial-interglacial as well as decadal timescales. That means the ISM is not the sole controlling factor of Chinese stalagmite δ18O during Heinrich events. When subtracting the Indian stalagmite δ18O series from our XL15 record during H1 period, we found a significant negative correlation with sea surface temperature (SST) record of Western Pacific Warm Pool (WPWP). Consequently, our study suggests that the Chinese stalagmite δ18O is controlled by both the ISM and EASM on orbital-, millennial-, and decadal timescales. [ABSTRACT FROM AUTHOR]

Summer precipitation in the north fringe of East Asian Summer Monsoon (NFEASM) accounts for the majority of annual regional precipitation and plays an important role in regional climatology and agriculture development. Here we analyze variations in summer precipitation in the NFEASM over the past millennium using several simulations with Earth System Models and compare with two dendroclimatological hydroclimate reconstructions that partly cover the past millennium. Both reconstructed records show good agreement on past hydroclimate variations but do not show overly anomalous hydroclimate periods, except for clear drying trends in the second half of the twentieth century. The reconstructed decadal hydroclimate variations are not correlated with any of the simulations, and the simulations are not correlated among themselves either, which strongly suggests that the decadal variability is not linked to the external climate forcing. In addition, the superposed epoch analysis also does not identify a response of simulated precipitation to volcanic eruptions. Therefore, precipitation variability in this region over the past millennium seems to have been driven by internal climate processes. In the simulations, regional summer precipitation is positively and significantly correlated with sea-level-pressure (SLP) over the North Pacific and is negatively and significantly correlated with SLP in southwestern China at both interannual and decadal time scales. This agrees with the teleconnection patterns identified from meteorological reanalysis datasets, indicating that this dipole correlation pattern is robust. Therefore, the SLP difference between these two areas is used as an index to identify the atmosphere circulation pattern favorable to summer precipitation in the NFEASM. This SLP index shows spatial variable correlations with sea-surface-temperature (SST) in the North Pacific: there is a significant positive correlation in the northern North Pacific, while a significant negative correlation in the southern North Pacific. Although the underlying mechanisms for these correlations likely differ between two subareas, it appears that the atmosphere drives SST anomalies in the both subareas. [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon (EASM) shows notable change during the summer after El Niño peak. This "delayed" response, however, is variable and difficult to predict. Here, we revisit this issue by separating El Niño decays into early transition and late transition. In the summer after an early transition, the central-to-eastern Pacific evolves into a La Niña condition, with positive rainfall anomaly occurring over most parts of eastern China. In contrast, in the summer after a late transition, the central-to-eastern Pacific sea surface temperature (SST) anomaly remains neutral or slightly above normal; correspondingly, the East Asian rainfall anomaly shows a tripolar structure with positive anomaly over the Yangtze-Huaihe River valley and negative anomalies over northern and southern China. These different rainfall responses are mainly related to different locations of the anomalous anticyclone (AAC) over the western North Pacific (WNP): it is centered at (165°E, 25°N) for late-transition El Niños, but at (135°E, 16°N) for early-transition El Niños. During the late transition, the AAC–SST feedback, identified by the dipole SST mode consisting of WNP cooling and northern Indian Ocean (NIO) warming, mainly works to support the WNP AAC. During the early transition, the AAC–SST feedback is weak and mainly attributed to NIO warming. The strong easterly anomaly over the western equatorial Pacific, which is tied to the central-to-eastern equatorial Pacific cooling and dipole precipitation pattern from western equatorial Pacific to the Maritime Continent, occurs to support the AAC and pulls it equatorward. These distinct responses exist in the last century, and the CMIP5 models can reproduce these distinct responses well except that the models underestimate the AAC–SST feedback for late-transition El Niños. The findings in this study help predict the EASM rainfall in post-El Niño years, but the key is the accurate prediction of the timing of decay. [ABSTRACT FROM AUTHOR]

The effects of urban land-use change in East China on the East Asian summer monsoon (EASM) are investigated using a Community Atmosphere Model Version 5.1. The results show that the urban land-use change in East China causes spatially-varying changes in surface net radiation and heat fluxes, atmospheric circulation, and water budgets. It results in significant surface warming (cooling) and precipitation decrease (increase) in a large region north (south) of 30°N. Urban expansion agglomerated in (29°-41°N, 110°-122°E) alters the surface energy budget and warms the surface, resulting in strengthened southwesterly airflow south of 25°N and increased convergence below the mid-troposphere between 20° and 30°N. A concomitant northward downdraft associated with the increased convection generates an anomalous high pressure north of 30°N. Meanwhile, the downdraft not only produces adiabatic warming but also inhibits the dynamic condition for precipitation formation. The anomalous high pressure formed in North China prevents the southwesterly airflow from advancing northward, leading to increase the convergence and precipitation in South China. These changes reduce the meridional temperature gradient in the mid-lower troposphere and weaken the westerly airflow near 30°N. In addition, horizontal transport of vorticity north of 35°N weakens significantly, which leads to an anomalous barotropic structure of anticyclonic there. As a result, the anomalous anticyclonic circulation and descent north of 30°N are strengthened. At the same time, the anomalous cyclonic circulation and ascent south of 30°N are enhanced. These process induced by the thermal state changes due to urbanization weakens the EASM. [ABSTRACT FROM AUTHOR]

The sensitivity of the East Asian summer monsoon to soil moisture anomalies over China was investigated based on ensembles of seasonal simulations (March-September) using the NCEP GCM coupled with the Simplified Simple Biosphere Model (NCEP GCM/SSiB). After a control experiment with free-running soil moisture, two ensembles were performed in which the soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China (YRNC) was double and half that in the control, with the maximum less than the field capacity. The simulation results showed significant sensitivity of the East Asian summer monsoon to wet soil in YRNC. The wetter soil was associated with increased surface latent heat flux and reduced surface sensible heat flux. In turn, these changes resulted in a wetter and colder local land surface and reduced land-sea temperature gradients, corresponding to a weakened East Asian monsoon circulation in an anomalous anticyclone over southeastern China, and a strengthened East Asian trough southward over Northeast China. Consequently, less precipitation appeared over southeastern China and North China and more rainfall over Northeast China. The weakened monsoon circulation and strengthened East Asian trough was accompanied by the convergence of abnormal northerly and southerly flow over the Yangtze River valley, resulting in more rainfall in this region. In the drier soil experiments, less precipitation appeared over YRNC. The East Asian monsoon circulation seems to show little sensitivity to dry soil anomalies in NCEP GCM/SSiB. [ABSTRACT FROM AUTHOR]

By using the monthly ERA-40 reanalysis data and observed rainfall data, we investigated the effect of the Indian summer monsoon (ISM) on the South Asian High (SAH) at 200 hPa, and the role played by the SAH in summer rainfall variation over China. It is found that in the interannual timescale the east-west shift is a prominent feature of the SAH, with its center either over the Iranian Plateau or over the Tibetan Plateau. When the ISM is stronger (weaker) than normal, the SAH shifts westward (eastward) to the Iranian Plateau (Tibetan Plateau). The east-west position of SAH has close relation to the summer rainfall over China. A westward (eastward) location of SAH corresponds to less (more) rainfall in the Yangtze-Huai River Valley and more (less) rainfall in North China and South China. A possible physical process that the ISM affects the summer rainfall over China via the SAH is proposed. A stronger (weaker) ISM associated with more (less) rainfall over India corresponds to more (less) condensation heat release and anomalous heating (cooling) in the upper troposphere over the northern Indian peninsula. The anomalous heating (cooling) stimulates positive (negative) height anomalies to its northwest and negative (positive) height anomalies to its northeast in the upper troposphere, causing a westward (eastward) shift of the SAH with its center over the Iranian Plateau (Tibetan Plateau). As a result, an anomalous cyclone (anticyclone) is formed over the eastern Tibetan Plateau and eastern China in the upper troposphere. The anomalous vertical motions in association with the circulation anomalies are responsible for the rainfall anomalies over China. Our present study reveals that the SAH may play an important role in the effect of ISM on the East Asian summer monsoon. [ABSTRACT FROM AUTHOR]

The variability of the East Asian winter monsoon (EAWM) can be divided into an ENSO-related part (EAW) and an ENSO-unrelated part (EAWM). The influence of EAWM on the ENSO-East Asian summer monsoon (EASM) relationship in the decaying stages of ENSO is investigated in the present study. To achieve this, ENSO is divided into four groups based on the EAWM: (1) weak EAWM-El Niño (WEAWM-EN); (2) strong EAWM-El Niño (SEAWM- EN); (3) weak EAWM-La Niña (WEAWM-LN); (4) strong EAWM-La Niña (SEAWM-LN). Composite results demonstrate that the EAWM may enhance the atmospheric responses over East Asia to ENSO for WEAWM-EN and SEAWM-LN. The corresponding low-level anticyclonic (cyclonic) anomalies over the western North Pacific (WNP) associated with El Niño (La Niña) tend to be strong. Importantly, this feature may persist into the following summer, causing abundant rainfall in northern China for WEAWM-EN cases and in southwestern China for SEAWM-LN cases. In contrast, for the SEAWM-EN and WEAWM-LN groups, the EAWMres tends to weaken the atmospheric circulation anomalies associated with El Niño or La Niña. In these cases, the anomalous WNP anticyclone or cyclone tend to be reduced and confined to lower latitudes, which results in deficient summer rainfall in northern China for SEAWM-EN and in southwestern China for WEAWM-LN. Further study suggests that anomalous EAWM may have an effect on the extra-tropical sea surface temperature anomaly, which persists into the ensuing summer and may interfere with the influences of ENSO. [ABSTRACT FROM AUTHOR]

There has been an increasing need to reconstruct past climate from proxy records quantitatively and mechanistically. The inverse proxy modeling method stands out as a novel approach to quantitative palaeoclimate reconstructions through integrating process-based models and proxy records, representing a major progress in quantitative palaeoclimatology. It has been proposed to incorporate multiple proxy records to produce a more robust constraint on the climate parameters sought for estimation, and most of the work has been conducted using pollen records in conjunction with vegetation models. Here, I show a worked example of using paired stable oxygen and carbon isotope records of peat cellulose from one single core to infer the climate history in NE China for the last 6000 years through solving a well-posed inverse problem using Bayesian statistics. The quantitative palaeoclimate data obtained in this study may deepen our insight into the dynamics of the East Asian summer monsoon. Mean growing season temperature and relative humidity show millennial-scale fluctuations prior to c. 4000 cal. yr BP; thereafter, centennial-scale fluctuations prevailed, revealing the relative importance of solar activity over tropical ocean–atmosphere interactions in regulating the variability of regional climate during the late Holocene. It appears that there was a prominent out-of-phase relationship between temperature and relative humidity, due probably to the different response of these climate elements to orbital forcing and land cover. This worked example demonstrates the potential of using model–data fusion techniques to produce physically meaningful, mathematically optimal, and geologically sound results. [ABSTRACT FROM PUBLISHER]

The first two series (RMM1 and RMM2) of RMM Index (all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter (preceding December to current February) MJO strength, according to which active (or inactive) years of preceding winter MJO are divided. By utilizing the data provided by NCEP/NCAR, CMAP and China's 160 stations from 1979 to 2008, we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation, i.e. when the preceding winter MJO is relatively active, the summer precipitation in the basin decreases, and vise verse. We also analyzed the causes. When the preceding winter MJO is relatively active, its release of potential heat facilities Inter-Tropical Convergence Zone (ITCZ) to strengthen and locate northward in winter and propagate northeastward. This abnormal situation lasts from winter to summer. In mid-May, ITCZ jumps northward to the South China Sea, the western Pacific subtropical high withdraws eastward, and the South China Sea summer monsoon sets off and strengthens. In summer, ITCZ propagates to South China Sea-subtropical western Pacific, the zonal circulation of subtropical Pacific strengthens, and a local meridional circulation of the South China Sea to the basin area forms, giving rise to the East Asia Pacific teleconnection wave-train. An East Asian monsoon trough and the Meiyu front show opposite features from south to north, the East Asian summer monsoon strengthens and advances northward. As a result, the summer monsoon is weakened as the basin is controlled by the subtropical high continually, with less rain in summer. On the contrary, when the preceding winter MJO is inactive, ITCZ weakens and is located southward, the subtropical high is located southward in summer, and the basin is in a region of ascending airflow with prevailing southwest wind. The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases. [ABSTRACT FROM AUTHOR]

Hourly summer precipitation data recorded at 21 stations during 1961-2004 in the Haihe River Basin in North China were analyzed. The results show that the precipitation frequency and amount and the morning peak mainly relating to long-duration rainfall events decreased during this period, whereas the normalized afternoon peak mainly relating to short-duration events increased, which may suggest that the proportion of short-duration rainfall has increased as the total summer rainfall has decreased. For short-duration events, the mean intensity and peak intensity increased at most stations and the time to peak intensity decreased, which may be attributable to the higher thermal contrast between the warmer lower surface and cooler upper level. In the case of long-duration events, the total amount was significantly correlated with the East Asian summer monsoon index for the period 1961-2001 (correlation coefficient of 0.63). Although the total amount of rainfall in long-duration events decreased in the basin, the mean intensity and peak intensity, as well as the extreme hourly precipitation, increased in the western basin and decreased in the eastern basin. [ABSTRACT FROM AUTHOR]

Changes of the frequency of precipitation extremes (the number of days with daily precipitation exceeding the 90th percentile of a daily climatology, referred to as R90N) in summer (June-August) over the mid-lower reaches of the Yangtze River are analyzed based on daily observations during 1961-2007. The first singular value decomposition (SVD) mode of R90N is linked to an ENSO-like mode of the sea surface temperature anomalies (SSTA) in the previous winter. Responses of different grades of precipitation events to the climatic mode are compared. It is notable that the frequency of summer precipitation extremes is significantly related with the SSTA in the Pacific, while those of light and moderate precipitation are not. It is suggested that the previously well-recognized impact of ENSO on summer rainfall along the Yangtze River is essentially due to a response in summer precipitation extremes in the region, in association with the East Asia-Pacific (EAP) teleconnection pattern. A negative relationship is found between the East Asian Summer Monsoon (EASM) and precipitation extremes over the mid-lower reaches of the Yangtze River. In contrast, light rainfall processes are independent from the SST and EASM variations. [ABSTRACT FROM AUTHOR]

Two lacustrine sporopollen records obtained from the Qaidam Basin (in the non-monsoonal region) and the Linxia Basin (in the monsoonal transition zone) indicate that during the early Pleistocene open forest-steppe/steppe vegetation developed in the Qaidam Basin, while in the Linxia Basin an open cypress forest-steppe shifted to a conifer/conifer-steppe and then to open forest-steppe vegetation. Existing sporopollen records from the Chinese Loess Plateau (CLP) (in the monsoonal region) indicate that around the Sanmen Paleolake open forest-steppe shifted to pine/conifer-broadleaved mixed forest. The conifer cover then changed to a subtropical evergreen broadleaved forest distributed around the Nihewan Paleolake. These changes suggest that wetter conditions progressed from western China to the east, and the climate became more humid than that of today indicating a stronger Asian summer monsoon during the early Pleistocene. [ABSTRACT FROM AUTHOR]

High-resolution oxygen isotope (δ18O) profiles of six stalagmites from Sanbao Cave in Hubei province, central China, established with 1413 oxygen isotope data and 65 230Th ages, provide a continuous history of East Asian Summer Monsoon (EASM) intensity for the period from 13-0.2 thousand years before present (ky BP, relative to AD 1950). The δ18O record includes four distinct stages in the evolution of the EASM: (1) an abrupt transition (∼11.5 ky BP) into the Holocene; (2) a period of gradual increase in monsoon intensity (11.5-9.5 ky BP); (3) the maximum humid period (9.5-6.5 ky BP); and (4) a period of gradual decline in monsoon intensity (6.5-0.2 ky BP). Comparison of Sanbao with regional records of comparable resolution reveals that the timing of the beginning and end of the Holocene Optimum (as defined by the minimum in δ18O) was similar in the Indian and East Asian monsoon systems. This supports the idea that shifts in the monsoon tied to shifts in the mean position of the Inter-Tropical Convergence Zone (ITCZ) may control monsoon intensity throughout the entire low-latitude region of Asia on orbital timescales. This observation also supports the idea that the fluctuations in δ18O recorded across southern Asia reflect broad changes in the monsoon, as opposed to local meteoric precipitation. The EASM records from Sanbao largely follow orbital-scale insolation changes, yet exhibit similar variability to Greenland ice core δ18O on millennial to centennial scales during the early to middle Holocene (&#x03B3l = 0.94). [ABSTRACT FROM AUTHOR]

Excessive rainfall was observed over Southwest China in July 2018, leading to floods in several major tributaries of the Yangtze River and landslide and debris flow in the neighboring provinces. The rainfall during 7–11 July was unusually heavy and broke the record that can be traced back to 1961. The occurrence of the excessive rain can be attributed to the anomalous convection over the western North Pacific and the presence of a mid-latitude Rossby wave train. On one hand, the convection over the western North Pacific was anomalously strong in July 2018, and it could have excited the negative phase of the Pacific–Japan pattern and led to a northwestward shift of the western Pacific subtropical high. Hence, the water vapor transport toward inland China including Southwest China was enhanced, providing a favorable moisture environment for precipitation. On the other hand, a mid-latitude Rossby wave train was observed to propagate from Northern Europe towards East Asia, which was conducive to anomalous ascending motion over Southwest China via warm advection and differential vorticity advection, creating a favorable dynamical condition for precipitation. As a result, the combination of the two effects mentioned above led to the occurrence of the flood over Southwest China in July 2018. [ABSTRACT FROM AUTHOR]