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Moisture sources and transport processes play a critical part in hydrological cycle and determine regional precipitation. This paper utilizes the Water Accounting Model‐2layers (WAM‐2layers) and the ERA5 reanalysis data to track the sources of precipitation over the Pearl River Basin (PRB). The contribution of external moisture and the role of local recycling are investigated. The results show that during the period from 1980 to 2020, oceanic sources including the western North Pacific and Indian Oceans serve as the primary moisture sources of precipitation over the PRB. The contributions to total seasonal precipitation are respectively 62.57% in MAM, 54.79% in JJA, 43.70% in SON and 60.88% in DJF. By contrast, the contribution of local recycling is generally below 5.50%. In the dry years of 1994, 1997 and 2001, the contribution of terrestrial sources is about 19.22%; in the wet years of 1989, 2009 and 2011, the contribution is about 16.31%. The summer precipitation anomalies are mainly attributable to moisture anomalies from the Equatorial Indian Ocean in the wet years and from Southeast Asia in the dry years. Furthermore, vertically integrated moisture flux anomalies over the boundaries of the PRB are generally the result of anomalous wind rather than anomalous moisture. In the wet years, low‐pressure systems induce strong cyclonic moisture transports, increasing the PRB precipitation. In the dry years, high‐pressure anomalies over the PRB block the moisture transports from the Indian Ocean and western North Pacific. [ABSTRACT FROM AUTHOR]

Increasing variability of precipitation induced by climate change raises uncertainties for ecosystem services and agricultural production in the Poyang Lake Basin (PLB), China. Reanalysis precipitation datasets (RPDs) are attractive alternatives for monitoring the hydro‐climate cycles. However, their applicability in China has mainly been evaluated at the national scale, while less attention has been paid to the PLB or southeastern China. Here, we apply various metrics to evaluate the magnitude and spatial similarity of annual, monthly, different intensities and the spatial structure of precipitation from four reanalysis—the fifth global atmospheric analysis dataset of the European Center for Medium‐Range Weather Forecasts (ECMWF) (ERA5), Interim ECMWF Reanalysis (ERA‐Interim), Japanese 55‐year Reanalysis project (JRA55) and Modern‐Era Retrospective analysis for Research and Applications, Version 2 (MERRA‐2), against the rain‐gauges over the PLB during 1980–2018. The results showed that the detection capacity of ERA5 and MERRA2 shifted around 2002, whereas that of ERA‐Interim and JRA55 did not substantially change. Before 2002, ERA‐Interim had the lowest biases for the magnitude of annual, monthly and different intensities of precipitation (except for heavy rain), while ERA5 and MERRA2 had strengths in capturing spatial correlation. Notably, ERA5 and MERRA2 had region‐wide wet and dry biases, respectively, before 2002, which can be attributed mainly to the estimation of flood season precipitation (from April to June) and heavy rain. In contrast, the fractional contribution of light–moderate rain was underestimated and overestimated by ERA5 and MERRA2, respectively. However, after 2002, because of the improved reproducibility of flood season precipitation and heavy rain magnitude, the systematic biases of ERA5 and MERRA2 significantly decreased, especially for ERA5, which outperformed other RPDs on all aspects of precipitation. The conclusions of this paper suggest that the variation of applicability over time should be seriously tested before the utilization of RPDs in hydro‐climate analyses. [ABSTRACT FROM AUTHOR]

In this paper, we evaluate a 48‐member multiphysics ensemble using the Weather Research and Forecasting (WRF) model for the JJA extreme precipitation and temperature in 2003 over the CORDEX‐EA‐II domain. The simulated precipitation and temperature are reasonable in the subregions controlled by a large‐scale circulation, yet the biases for both precipitation and temperature are evident over the subregions where the effects of mesoscale processes are important. The performance of various combinations of WRF physical schemes for simulating the JJA precipitation is dependent on the region. Meanwhile, the cumulus and microphysical schemes have substantial influences on the simulation of precipitation, and the land surface models and cumulus schemes play crucial roles in the surface temperature. Our analysis shows that the combination of Noah for the land surface process, Lin for the microphysics, G3D for the cumulus parameterization, and CAM for the radiation scheme can provide the most reliable reproduction of both precipitation and temperature extremes over China. Ensemble analysis shows that the simulated climate extremes are usually accompanied by a large ensemble spread, implying sensitivities to the model physical processes in some subregions. The simulated wind fields at low‐to‐middle atmospheric levels display responses to the options of the land surface models and cumulus schemes. The essential impact of the land–atmospheric interaction on simulating the extremes can be largely attributed to the active convective processes. WRF has difficulties in reproducing the observed temporal evolution of the rainfall process, which consists of continuous large rainfall episodes in the observation data set during the simulation period. [ABSTRACT FROM AUTHOR]

Various climatic factors and their interactions affect China's snow depth alterations. However, a measure of the relative importance of climatic factors regarding the variance in snow depth is lacking. Here, we use a heretofore largest dataset, quality‐controlled daily observations from 1,665 meteorological stations, and statistical analyses to identify proxy drivers and their contributions regarding regional variability and trends in China's snow depth and snow depth‐climate relationships from 1951 to 2019. Results show that seasonal snow depth alterations are substantial in China and caused by various climatic drivers. In winter, observed positive trends in the northwest and northeast of China mainly respond to augmentation in solid precipitation and snow accumulation in fall. For the Tibetan Plateau, the negative snow depth anomaly seems to respond to the rising air temperature below the freezing point along with some secular changes in solid precipitation and shallower fall snowpacks. All these trends in winter snow depth over the northwest, northeast, and Tibetan Plateau of China account approximately for 30% of the total interannual variance in spring snow depth in these regions. In the milder central north and south of China, snow accumulation is not evident. Besides solid precipitation and rising air temperature below the freezing point, atmospheric humidity is also notable for its effect on the interannual variance in winter snow depth in these regions. In spring and fall, however, the negative effect of warming climate on snow depth becomes remarkably more important. It seems that about 13–33% (12–50%) of the total interannual variance in the widespread decrease (insignificant perturbation), except for some weak increases in the northeast region (decreases in the Tibetan Plateau), of China's spring (fall) snow depth are caused by the rising air temperature below the freezing point. [ABSTRACT FROM AUTHOR]

Understanding and exploring hydrological (H) or soil moisture (SM) drought due to meteorological (M) drought under changing climate is crucial for drought early warning. Previously, different methods were used to calculate drought propagation from one state (M to another [H or SM]). However, each method has its pros and cons and thus cannot describe appropriate propagation attributes. In this study, a time series analysis is carried out to explore the propagation process in the Yellow River Basin (YRB) and Hai River Basin (HRB) of China. Standardized Streamflow Index (SSI), Standardized SM Index (SSMI), and Standardized Precipitation Index (SPI) 1‐month time series were calculated using streamflow, satellite‐based SM, and precipitation from 1979 to 2016. The time series framework identifies the average drought propagation as 3.4–8.3 months (M–H) and 2.3–5 months (M–SM) in YRB, while 2.8–7.7 months (M–H) and 2.3–8.5 months (M–SM) in HRB. Cross‐wavelet analysis indicated that periodic characteristics of M drought are responsible for these droughts. Overall, the findings of this study may help to minimize the drought hazards posed by M droughts. [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]

Hindcasts during 1991–2010 are analysed to investigate the forecast skills for summer precipitation in northeast China (NEC) and circulations in northeast Asia with a leading time of 1‐month in three operational climate models and their equally weighted mean. It is found that the precipitation prediction ability of all the models and their combinations are much low in NEC. However, both the single model and their averages can well reproduce the basic summer circulation characteristics over Northeast Asia, especially the northeast China cold vortex (NECV) that directly affects precipitation in NEC. Observed precipitation is significantly correlated with the forecasted vorticities in each model and their combinations, particularly in the ensemble mean of the models (MME). Furthermore, the interannual variability of the NECV in MME agrees well with the observations. Linear regression between the simulated NECV and the precipitation in NEC is established for each model and their averages. The root‐mean‐square errors (RMSEs) of precipitation forecast from the regression of NECV are much lower than the direct outputs in above models, while the correlation coefficients (CCs) are much higher. The CC between observation and forecasts by the regression method based on the NECV in MME is the highest (0.5), closest to the value of 0.58 in observation, and the RMSE is the smallest (0.54), decreased by 13% compared with MME direct outputs. The cross‐validation during the 20 years can provide better prediction skills with a CC of 0.37, higher than that for the single‐model outputs, the averages of random two models and the MME. Independent forecasts also provide higher prediction skills than the official forecast of China Meteorological Administration in 4 years during 2013–2018, especially the extreme flood summer of 2013. The results indicate it might be a feasible approach to improve the prediction skill of summer precipitation in NEC. [ABSTRACT FROM AUTHOR]

Northeast China is a major agricultural production base in East Asia, and spring is the agricultural ploughing season throughout the region. The precipitation in spring is therefore significant to agricultural activity and production in the region. In this study, the interdecadal variation in spring precipitation across northeast China is investigated. In the past four decades, there has been a significant increase in spring precipitation in northeast China, and the increase in May precipitation made a dominant contribution to that increase. Further analysis indicates that the increase in May precipitation is concurrent with the decline in Arctic sea ice concentration (SIC) over the Barents Sea; both variables show an interdecadal shift around the early 2000s. Physical analysis based on observations and numerical simulations demonstrates that a decline in the Barents Sea SIC could excite a Rossby wave train propagating southeastward across the Mongolia‐Baikal region and reaching northeast China, thereby inducing a zonal anticyclone–cyclone–anticyclone teleconnection pattern over mid‐ to high‐latitude Eurasia. Under the influence of such a teleconnection pattern, significant southerlies prevail over northeast China, bringing warm and wet air to the region; in addition, the local atmospheric instability and upward motion are also increased. The changes in the moisture and dynamic conditions favour the increase in May precipitation over northeast China. Furthermore, SIC anomalies in the Barents Sea persist from late winter to spring; therefore, the SIC signal could provide signals for predictions of the interdecadal changes in May precipitation over northeast China. [ABSTRACT FROM AUTHOR]

Many studies found that land use change (LUC) had great impacts on regional precipitation, due to thermodynamic and dynamic responses. However, the relative contributions of these two factors to changes in precipitation due to LUC are rarely investigated. This study quantifies the relative contributions of thermodynamic and dynamic to the changes of mean and extreme precipitation due to LUC based on simulations of the Weather Research and Forecasting (WRF) model. The Yangtze River Basin (YRB) is used as a case study, as it has experienced great LUC during the past decades. Four land use scenarios (two factual cases and two hypothetical reforestation scenarios) were used to test the sensitivity of precipitation changes to LUC. Changes in mean and extreme precipitation over the YRB for all seasons are attributed to thermodynamic and dynamic changes using 500‐hPa geopotential height and precipitation data derived from the simulations of WRF. The results show that the factual process of LUC results in a decrease in summer mean daily precipitation and precipitation extremes in most areas of the YRB (except for the middle reaches of the YRB), while the hypothetical reforestation contributes to an increase in summer mean and extreme precipitation, and the impacts of reforestation on increasing precipitation are limited. The thermodynamic change contributes to an increase in seasonal mean daily precipitation, extreme precipitation totals and occurrence frequency of precipitation extremes with contributions ranging from 94 to 102%, which is the main contributor of changes in precipitation due to LUC. The dynamic change only makes a small contribution to the change of precipitation. Because the contributions of thermodynamic can be offset by dynamic changes to changes in precipitation, it could result in minimal changes in precipitation and occurrences of precipitation extremes. [ABSTRACT FROM AUTHOR]

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]

It is very important to identify the possible mechanism of precipitation generation in southeastern China. To determine the weather type (WT) that is likely to generate precipitation, the Jenkinson–Collison classification method was applied to wintertime daily mean sea level pressure data across southeastern China. We found that all WTs with easterly components are prone to generate precipitation. These WTs were merged into one type named the ensemble of easterly wind components (the EE type). The persistence and transformation rules of the EE type are studied. Anticyclone type is the easiest one to convert to EE type. The persistence and transformation rules of the EE type provide favourable conditions for the formation of precipitation. Furthermore, we examined the influence of two common teleconnections (Western Pacific [WP] and Eurasian [EU]) in East Asia in winter on the WTs. When WP is in the positive phase and EU is in the negative phase, EE type weather patterns will appear frequently in southeastern China. At this time, it is most conducive to the formation of precipitation. On the one hand, warm and cold air converge in this area. On the other hand, the prevailing east wind can provide sufficient water vapour. The study implies that whether a WT is easy to produce precipitation can be judged by wind direction. The results will help us better understand the physical mechanism of precipitation generation in this area. [ABSTRACT FROM AUTHOR]

The dry‐wet climate conditions of an area are mainly determined by the water input (e.g., precipitation, P) and output (e.g., potential evapotranspiration, PET). Based on three dry‐wet indices and the differential equation, this study designed a new attribution method to quantify the contributions of P and PET to the dry‐wet change, so as to determine the dominant factors of the dry‐wet change over whole China (CHINA) and various hydroclimate regions (i.e., arid region, AR; semi‐arid region, SAR; semi‐humid region, SHR; and humid region, HR) during 1960–2018 and six interdecadal periods. Results showed that the overall weak drying in CHINA was dominated by an increase in PET, while climate humidification in AR and HR was dominated by an increase in P, climate drying in SHR was dominated by the reduced P, and the weak drying in SAR was co‐dominated by P and PET during 1960–2018. The dominant factors of dry‐wet change over CHINA and each hydroclimate region varied in different decades. Briefly, climate humidification in CHINA and various hydroclimate regions was basically dominated by P in different decades, and the drying was mainly dominated by P in the 1960s–1980s, but the contribution of PET to climate drying began to become prominent after the 1980s. Besides, we found that P contributed more to dry‐wet change than PET on the station and regional scales, but the contribution of P to climate drying on a national scale was underestimated to some extent due to the regional offset effect of the increase/decrease in P during 1960–2018, as well as in the 1990s. These findings implied that the importance of research on the regional or local scale, and equal attention should be paid to the effects of P and PET changes in the future drought or dry‐wet change research. [ABSTRACT FROM AUTHOR]

As one of the most influential oceanic and atmospheric oscillations in the Earth system, El Niño‐Southern Oscillation (ENSO) has modulated numerous geophysical processes. This is particularly true for the Yangtze River Basin (YRB), which is vulnerable to Asian Monsoon and faces serious hydrological hazards. In this study, the co‐variability between lag–lead precipitation and sea surface temperature anomalies was evaluated utilizing singular value decomposition (SVD) method. Moreover, certain teleconnections between ENSO and streamflow were identified by wavelet methods. In addition, the contribution of related atmospheric variables was revealed by composite analysis. Results indicate that there are strong associations in lag–lead seasons between the wet condition (dry condition) and September–November (December–February) mature ENSO phase. Significant common power and coherence signals between the ENSO indices and the streamflow occur in the 4–8, 8–16 and 16–32 seasonal scales. Meanwhile, the activity cycle of the ENSO indices ahead of streamflow increases from the mid‐lower reaches to the source region. In addition, the Western Pacific Subtropical High is strengthened during the mature ENSO phase. Anomalous sinking motions and divergent water vapour flux occupy the YRB, reducing the precipitation and leading to the dry condition in the source region until the following March–May. On the other hand, ascending movements and abundant water vapour flux coming from northern Pacific, equatorial western Pacific and the Bay of Bengal result in the wet condition in the mid‐lower reaches. [ABSTRACT FROM AUTHOR]

Previous studies suggested that sea surface temperature (SST) anomalies in the tropical central‐eastern Pacific (TCEP) and tropical Northern Atlantic (TNA) both have significant impacts on the inter‐annual variation of precipitation over the monsoon transitional zone (MTZ) in China during August–September. This study further reveals that the relationship between TCEP (TNA) SST and MTZ precipitation during August–September is strongly modulated by the sign of the TNA (TCEP) SST. When TCEP and TNA SST anomalies have the same sign, connections of the TCEP and TNA SST with the MTZ precipitation are unclear. In contrast, TCEP and TNA SST changes both have significant relation with the MTZ precipitation when they have the opposite sign. During the same‐sign years, the anticyclonic (cyclonic) anomaly over the western North Pacific generated by the TCEP SST cooling (warming) is weakened by the cyclonic (anticyclonic) anomaly triggered by the TNA SST cooling (warming). Thus, connections of the MTZ precipitation with the TCEP and TNA SST are weak. However, during the opposite‐sign years, the anticyclonic anomalies over the western North Pacific generated by the TCEP SST anomalies have a constructive superposition on those induced by the TNA SST changes. As such, connections of the TCEP and TNA SST with the MTZ precipitation variation are significant. Further analysis shows that the prediction skill of precipitation over the MTZ is enhanced if taking both the TCEP and TNA SST signals into account. [ABSTRACT FROM AUTHOR]

ABSTRACT On the basis of the datasets obtained for the monthly turbulent heat flux (1984-2009) from the Objectively Analyzed Air-Sea Heat Flux (OAFlux), the radiation flux from the International Satellite Cloud Climatology Project (ISCCP), the variability characteristics of the net heat flux (Qnet) over the Kuroshio System (KS) and its relationship with the climate in China were studied. The results reveal that except for a steady enhancement in the period 1984-2009, the boreal winter Qnet over the KS is characterized by obvious interannual variation of the period quasi-5 year as well as decadal variability shifting from negative to positive anomalies in the mid-1990s. In the wintertime, the increasing KS Qnet is primarily responsible for the intensification of the East Asia winter monsoon (EAWM) via a deepening of the Aleutian low and an enhancement of the Siberia high and has a correlation coefficient of 0.72 with a 1-month delay. The enhanced-EAWM induces colder winters in Northeast China and higher Qnet over the KS by carrying significantly greater amounts of cold air mass. During the low Qnet winter, the EAWM is weakened, and the southwesterly wind that contains abundant water vapour enhances and pushes toward southern China, thereby bringing heavier rainfall. The anomalous Qnet over the KS in the wintertime lasts until the following spring with a weaker relative intensity. In the spring after the low KS Qnet winter, the anomalous easterly wind transfers colder air masses from the Sea of Japan to the North China and Yellow-Huaihe regions and then cools these regions. The warmer and wetter southwesterlies along the northwestern flank of the anomalous anticyclone east of Taiwan Island meet these colder easterlies accompanied by an anomalous upward motion, thereby inducing an anomalous northwest-southeast precipitation band in the central and eastern region of China, especially in the Yangtze-Huaihe region. [ABSTRACT FROM AUTHOR]

ABSTRACT Daily precipitation data from 34 weather stations in Northeast China from 1960 to 2008 are used to examine trends in the occurrence of dry days and prolonged dry episodes. Trends in the mean length and frequency of prolonged dry episodes, as well as the number of dry days within prolonged dry episodes ( DDPDE), are computed regionally and for individual stations at the threshold levels of 1 and 2 mm day−1. Regionally, the number of dry days is increasing in the summer half-year and decreasing in the winter half-year. DDPDE is significantly increasing in the summer half-year; the increased frequency of dry spells has the greatest effect. The mean length of prolonged dry episodes in the winter half-year has decreased significantly. Our results indicate that neither the frequency nor the mean length of prolonged dry episodes, alone, can adequately describe the short-term dry conditions of an area. Multiple characteristics of dry spells, including frequency, length, and the number of DDPDE should be considered. DDPDE is a function of both the frequency and length of dry episodes, but may be more influenced by one or the other characteristics of dry spells, depending on the season or region. [ABSTRACT FROM AUTHOR]

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A millennium-long tree-ring-width chronology from the middle Qilian Mountains in northwestern China has been used to reconstruct annual precipitation variation (from the prior August to current July) since AD 775. The reconstruction explains 37.8% of variance of the observed data. Based on the mean and standard deviation of the reconstructed series, several prolonged severe dry and wet periods were indentified: drought spells in AD 1144-1154 (11 years) and 1925-1932 (8 years) and wet spells in AD 985-999 (15 years), 1089-1097 (9 years) and 1979-1991 (12 years). Both multi-taper spectral analysis (MTM) and wavelet analysis suggest that periods of the reconstructed precipitation are consistent with those associated with the Asian Summer Monsoon and perhaps solar activity. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The article presents a study which examines various processes which affect the dryness and wetness of the Tibetan plateau's boreal summer variability. The ERA-40 reanalysis was used to observe the precipitation on the plateau and analyze how surface temperature and atmospheric circulation influenced drought and wetness experienced in the Tibetan plateau. The study indicates that upstream and downstream Tibetan plateau conditions manifest importance for developing south-eastern Asian rainfall.