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Precipitation plays a crucial role in the global energy and water cycle and has important implications for food, water, and energy security. To enhance our understanding of the water cycle, it is invaluable to have a comprehensive historical record of precipitation. However, obtaining such records, especially for the period before the Industrial Revolution, can be challenging. During the Joseon Dynasty, Korea established a network for measuring rainfall and recorded this information in historical documents known as Seungjeongwon Ilgi and Ilseongnok. Recently, these documents have been digitized, providing us with daily precipitation data for Seoul spanning 130 years, from 1778 to 1907. By combining and analyzing these two documents, we were able to address inconsistencies found in previous studies and improve the quality of the data. Notably, this dataset is free of any missing values, making it the longest daily precipitation record in the world before the Industrial Revolution. Its availability to the public holds great potential for climate research in East Asia during the late Little Ice Age. [ABSTRACT FROM AUTHOR]

Regional hydrological cycle responding to rising temperatures can have significant influences on society and human activities. We suggest a new perspective on East Asia's enhanced precipitation amount that emphasizes the role of Siberian surface warming. Increased vegetation greenness in late spring and early summer in eastern Siberia, which may be a response to global warming, acts to warm the surface by reducing the surface albedo with an increase in net absorbed shortwave radiation. Subsequently, eastern Siberia warming leads to the strengthening of anti-cyclonic atmospheric circulation over inner East Asia as well as the subtropical western North Pacific high via thermal forcing and the enhanced land-sea thermal contrast, respectively. Consequently, the anticyclonic circulation over inner East Asia transports much drier and cooler air to southern East Asia. This leads to favorable conditions for increased precipitation in combination with an increased tropical moisture flux from the subtropical western North Pacific high. Therefore, continuous Siberian vegetation growth has a potential influence on the future precipitation amount in the subtropics through vegetation–atmosphere coupled processes. [ABSTRACT FROM AUTHOR]

Climate change exacerbates the threat of water scarcity over the drylands in East Asia (DEA), the world's most densely populated arid region. The water cycle continuously supplies water to support all life. Previous studies have focused on the change in individual hydrological components over DEA; however, how the projected water cycle changes under climate warming remains unclear. We demonstrate the projected response of the water cycle to global warming in different seasons utilizing the Coupled Model Intercomparison Project Phase 6. Winter in the DEA presents an intensification of the water cycle, reflected in coherent increases in evapotranspiration (E), precipitation (P), runoff, and surface soil moisture. In contrast, summer will experience a weakened water cycle in the northwestern DEA, while the southeastern part exhibits the opposite trend. From the surface and atmospheric water balance perspective, we further attribute the changes in E and P to gain a more comprehensive understanding. The increasing E is attributed to the combined effects of P and the vapor pressure deficit during summer, whereas it is dominated by P in winter. The increased P in summer is primarily attributed to the horizontal dynamic and vertical thermodynamic components associated with the strengthening and westward expansion of East Asia summer monsoon in the future. During winter, the increased P is mainly due to the vertical dynamic and horizontal thermodynamic components associated with the enhancement of vertical ascending motion and increased moisture. Plain Language Summary: Water scarcity threatens 1–2 billion people living in drylands worldwide, with drylands in East Asia (DEA) having the largest population. Future climate change can alter the availability of water resources by altering the water cycle. Therefore, analyzing the water cycle's response to global warming during both summer and winter is vital for water management and climate adaptation, particularly in DEA. Under a high‐emissions scenario, winter will experience an intensified water cycle, manifested as coherent increases in evapotranspiration (E), precipitation (P), runoff, and surface soil moisture. In summer, a weakened water cycle is anticipated in northwestern DEA, while southeastern DEA is expected to show the opposite trend. Furthermore, we offer a quantitative attribution of the response of E and P to global warming to gain a more profound understanding. The attribution of E indicates that the supply of energy and water commonly dominate the increase in E during summer. The attribution of P illustrates that the westward expansion of the monsoon with enhanced southeastern winds favors increased P during summer. In winter, strengthened vertical ascending motions and increased water vapor content provide favorable conditions for enhancing P. Water cycle intensification is accompanied by more frequent extreme events, necessitating increased attention. Key Points: Future global warming will intensify the water cycle of drylands in East Asia in winterDuring summer, evapotranspiration will increase due to precipitation and vapor pressure deficit; in winter, it is dominated by the formerIn winter and summer, the dominant roles of the dynamic and thermodynamic components influencing future precipitation are different [ABSTRACT FROM AUTHOR]

The long-range transport of bioaerosols by dust events significantly impacts ecological and meteorological networks of the atmosphere, biosphere, and anthroposphere. Bioaerosols not only cause significant public health risks, but also act as efficient ice nuclei for inducing cloud formation and precipitation in the hydrological cycle. To establish risk management for bioaerosol impacts on the Earth system, a large-scale investigation of bioaerosols must be performed under different environmental conditions. For this purpose, a Dust–Bioaerosol (DuBi) field campaign was conducted to investigate the distribution of bioaerosols by collecting ∼950 samples at 39 sites across East Asia from 2016 to 2021. Concentrations and community structures of bioaerosols were further analyzed using fluorescence microscopic observations and high-throughput DNA sequencing, and these factors were compared to environmental factors, such as PM10 and aridity. The results indicated that microbial concentrations at dryland sites were statistically higher than those at humid sites, while the microbe-to-total-particle ratio was statistically lower in drylands than in humid regions. Microbial cells per microgram of PM10 decreased when PM10 increased. The proportion of airborne particles at each site did not vary substantially with season. The richness and diversity of airborne bacteria were significantly higher in drylands than in semiarid regions, while the community structures were stable among all sampling sites. The DuBi field campaign improves our understanding of bioaerosol characteristic variations along the dust transport pathway in East Asia and the changes of bioaerosols under the trend of climate warming, supporting the efforts to reduce public health risks. SIGNIFICANCE STATEMENT: We first conducted large-scale Dust–Bioaerosol (DuBi) field observations in East Asia from 2016 to 2021. We used unified sampling and analysis methods to collect 950 samples at 39 sites and analyzed bioaerosols' concentration and community structure. This study aims to find the relationship between bioaerosols with atmospheric particles and aridity, which fills gaps in the field. These results improve our understanding of bioaerosols' impacts on ecological and meteorological networks of the atmosphere, biosphere, and anthroposphere. The comprehensive observations will promote prediction of bioaerosol change under the trend of climate warming, supporting the efforts to reduce global climate, ecological security, and public health risks in the future. [ABSTRACT FROM AUTHOR]

The Early Eocene Climatic Optimum (EECO) may be a potentially useful analog for future global warming under high CO2 concentrations. However, a paucity of orbital‐scale terrestrial records limits our understanding of how the hydrological cycle responded during this protracted (∼4 Myr) interval of global warmth. In this study, we combine zircon U‐Pb dating and cyclostratigraphy to establish a high‐resolution astronomical timescale spanning the EECO (∼52.9 Ma to ∼49.9 Ma) through a >1 km fluviolacustrine succession from the Gonjo Basin, Southeast Tibet. Our results suggest that hydroclimate variability in the region during this interval was strongly controlled by eccentricity forcing (∼405 Kyr, ∼135–100 Kyr, and possibly ∼200 Kyr cycles). The dominance of eccentricity forcing in our record is consistent with coeval marine records, and indicates that modulation of low‐latitude summer insolation through nonlinear interactions with the global carbon cycle likely controlled hydroclimate and paleolake level in the Gonjo basin during the EECO. Our study offers new perspectives for the forcing mechanisms of terrestrial hydroclimate changes of East Asia in response to subtle changes in insolation during the EECO. Plain Language Summary: High resolution and relatively long‐duration terrestrial paleoenvironmental records across an interval of extreme warmth ∼50 million years ago (called the EECO) are rare, limiting our understanding of how the hydrological cycle operated during this time interval. In this study, we present high‐resolution geochemical data through a succession of continental sedimentary rocks from the Gonjo Basin (Southeast Tibet) spanning the EECO. Our data suggest that EECO hydroclimate was dominated by climate forcing controlled by variations in Earth's eccentricity, emphasizing the importance of eccentricity modulation of low‐latitude summer insolation through nonlinear interactions with the global carbon cycle. This finding is consistent with coeval marine records. Our study provides new insights into the forcing mechanisms of terrestrial paleoclimate change in East Asia under warm climate conditions and high CO2. Key Points: Astronomical timescale spanning the Early Eocene Climatic Optimum (EECO) established in East Asia terrestrial recordRelatively wetter and warmer climate during ∼52.9–52.39 Ma and ∼50.34–49.9 MaEccentricity forcing of EECO terrestrial climate, consistent with coeval marine records [ABSTRACT FROM AUTHOR]

Atmospheric rivers (ARs) in East Asia have garnered increasing attention for their crucial roles in understanding extreme precipitation events and regional hydrological cycles. Here, we investigate the summer AR frequency over the East Asia‐western North Pacific region (EA‐WNP) during 1959–2022. Interestingly, the results show that the AR frequency over the two regions experienced opposite variations, with the boundary between them at around 135°–140°E. On interdecadal timescales, such variations are mainly synchronized with a zonal dipole pattern characterized by cyclonic (anticyclonic) anomalies centered to the northwest of Taiwan and anticyclonic (cyclonic) anomalies centered to the southeast of Japan. This interdecadal dipole pattern is induced by interdecadal changes in the western North Pacific subtropical high under different Pacific Decadal Oscillation (PDO) phases. Particularly, the internal variability accounts for about 77–90% of the observed trends in high response areas. The displacements of ARs are also consistent with the opposite trends of precipitation over EA‐WNP. ARs exert a dominant influence on the precipitation trend in the WNP region but a weaker contribution to the precipitation trend in the EA region, which reflects the different impacts of ARs on EA and WNP precipitation. These results indicate that the PDO has the potential for predicting EA‐WNP ARs on interdecadal timescales, and the opposite AR trends are crucial in understanding the complexity of precipitation over the EA‐WNP region. Plain Language Summary: Atmospheric rivers (ARs) are long, narrow corridors of intense water vapor transport, and considered a crucial source of extreme precipitation events and floods over coastal regions. Previous research has revealed southward‐shifting trends of ARs over East Asia (EA) in recent decades. However, the possibility of opposing AR trends within different areas of the entire EA and western North Pacific region (EA‐WNP) has not previously been considered. In this study, we examine the summer AR frequency over EA‐WNP based on reanalysis data during the past six decades. The results show that EA‐WNP ARs have experienced opposite interdecadal variations and formed opposite trends between EA and the WNP during specific periods. Further analysis reveals that these interdecadal shifts of ARs can be explained well by a zonal dipole pattern modulated by the interdecadal change in the western North Pacific subtropical high under a strong influence of the Pacific Decadal Oscillation. Moreover, such AR variations have caused opposite precipitation trends in EA‐WNP and contributed differently to the formation of the distinct precipitation regimes in EA and the WNP. These findings provide insights into the decadal prediction of ARs and their diverse roles in shaping regional precipitation variations over the EA‐WNP region. Key Points: Summer atmospheric rivers (ARs) over East Asia and the western North Pacific (EA‐WNP) have experienced opposite trends in recent decadesOpposite AR trends are modulated by a zonal dipole pattern, which correlates closely with the Pacific Decadal OscillationSuch AR variations lead to opposite precipitation trends and contribute differently to the precipitation regimes between EA and the WNP [ABSTRACT FROM AUTHOR]

The East Asian Summer Monsoon (EASM) provides the majority of annual rainfall to countries in East Asia. Although state-of-the-art models broadly project increased EASM rainfall, the spread of projections is large and simulations of present-day rainfall show significant climatological biases. Systematic evapotranspiration biases occur locally over East Asia, and globally over land, in simulations both with and without a coupled ocean. This study explores the relationship between evapotranspiration and EASM precipitation biases. First, idealized model simulations are presented in which the parameterization of land evaporation is modified, while sea surface temperature is fixed. The results suggest a feedback whereby excessive evapotranspiration over East Asia results in cooling of land, a weakened monsoon low, and a shift of rainfall from the Philippine Sea to China, further fueling evapotranspiration. Cross-model regressions against evapotranspiration over China indicate a similar pattern of behavior in Atmospheric Model Intercomparison Project (AMIP) simulations. Possible causes of this pattern are investigated. The feedback is not explained by an overly intense global hydrological cycle or by differences in radiative processes. Analysis of land-only simulations indicates that evapotranspiration biases are present even when models are forced with prescribed rainfall. These are strengthened when coupled to the atmosphere, suggesting a role for land-model errors in driving atmospheric biases. Coupled atmosphere-ocean models are shown to have similar evapotranspiration biases to those in AMIP over China, but different precipitation biases, including a northward shift in the ITCZ over the Pacific and Atlantic Oceans. [ABSTRACT FROM AUTHOR]

For more than a decade, GRACE data have provided global mass redistribution measurements due to water cycles, climate change and giant earthquake events. Large earthquakes can yield gravity changes over thousands of kilometres from the epicentre for years to decades, and those solid Earth deformation signals can introduce significant biases in the estimate of regional-scale water and ice mass changes around the epicentres. We suggest a modelling scheme to understand their contribution to the estimates of water and ice mass changes and to remove the earthquake-related solid mass signals from GRACE data. This approach is composed of physics-based earthquake modelling, GRACE data correction and high-resolution surface mass change recovery. In this study, we examined the case of the 2011 Tohoku–Oki earthquake to better estimate the regional sea level and hydrological mass changes in the East Asia. The co- and post-seismic changes from GRACE observations were used to constrain the earthquake model parameters to obtain optimal self-consistent models for the earthquake source and the asthenosphere rheology. The result demonstrated that our earthquake correction model significantly reduced the mass change signals by solid Earth deformation from the time-series of regional surface mass changes on both land and oceans. For example, the apparent climate-related ocean mass increase over the East Sea was 1.59 ± 0.11 mm yr−1 for 2003–2016, significantly lower than the global mean ocean mass trend (2.04 ± 0.10 mm yr−1) due to contamination of the earthquake signals. After accounting for the solid mass changes by the earthquake, the estimate was revised to 1.87 ± 0.11 mm yr−1, that is increased by 20 per cent and insignificantly different from the global estimate. [ABSTRACT FROM AUTHOR]

The springtime persistent rainfall (SPR) is the major rainy period before the onset of summer monsoon in East Asia, which profoundly affects the regional and even global hydrological cycle. Despite the great importance of the mechanical and thermal effects of the Tibetan Plateau (TP) large-scale orography on the formation of SPR, the impact of small-scale orography over the TP remains poorly understood. Here we show that upward-propagating orographic gravity waves (OGWs), which occur as the subtropical westerlies interact with the TP's small-scale orography, contribute importantly to the SPR. The breaking of OGWs induces a large zonal wave drag in the middle troposphere, which drives a meridional circulation across the TP. The rising branch of the meridional circulation acts to lower the pressure and increase the meridional pressure gradient to the south of the TP by dynamically pumping the lower-tropospheric air upwards. The southwesterly monsoonal flow on the southeastern flank of the TP thus intensifies and transports more water vapor to East Asia, resulting in an enhancement of the SPR. This finding helps more completely understand the impacts of TP's multiscale orography on the SPR and provides a new perspective on the westerly-monsoon synergy in East Asia. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) is a crucial parameter in the process of the hydrological cycle. It is vital for water resource management in the Xiangjiang River Basin (XRB) within Hunan Province of China to explore the spatial and temporal dynamic characteristics of ET. Based on MOD16, this study revealed the characteristics of spatiotemporal patterns of ET in the XRB from 2000 to 2020. We first applied land use data and change rate for overall trend analysis on ET. Then, we obtained migration routes of ET through standard deviation ellipse (SDE). Furthermore, we demonstrated the effects of monsoon and urban expansion on ET change. The results showed: (1) while the ET of artificial surfaces decreased the change rate in most regions of the XRB was 8.83%, indicating that the overall trend of ET in the XRB was increasing. (2) At 10-year intervals, the SDE center of ET all migrated in a clockwise direction. (3) The correlation between precipitation and ET is more obvious than that between temperature and ET. (4) With the influence of monsoon on precipitation in East Asia, the changes in precipitation are consistent with the ET change. [ABSTRACT FROM AUTHOR]

When projecting future monsoon changes by carbon dioxide (CO2) pathway, most studies have analyzed precipitation responses without considering monsoon area (total area of monsoon domain, MA) variations. However, how MA responds to CO2 removal remains uncertain. This study evaluates MA variations and impacts in idealized CO2 ramp‐up (toward CO2 quadrupling), ramp‐down, and stabilized simulations using the Community Earth System Model version 1. Global MA negatively overshoots (i.e., recovery with decreasing tendency beyond the original MA) during the ramp‐down period due to reduced or rapidly recovered MA in several regional monsoons, including Northern and Southern Africa, South and East Asia, and South America, showing hysteresis when comparing CO2 ramp‐up and ramp‐down periods despite similar global warming levels. These non‐linear regional MA variations come from distinct regional summer and winter precipitation variations, which are found to be mostly associated with Intertropical Convergence Zone movements and El Niño‐like response. Further, regional monsoon precipitation characteristics also vary through CO2 ramp‐up and ramp‐down periods consistently with overall hysteresis. Changes in total monsoon precipitation resemble the distinct responses of MA. Our results suggest that regions characterized by a monsoonal climate may experience reduced seasonal rainfall variations under net‐negative CO2 emissions. Plain Language Summary: Many studies have researched how increasing carbon dioxide (CO2) affects monsoon. Most have focused on precipitation changes without considering how monsoon area (i.e., total area of monsoon domain, MA) will change. Furthermore, it is unknown how global and regional MA responds to CO2 removal. In this study, we first investigate how global to regional MA changes under CO2 concentration increase, decrease and then equilibration using climate model simulations. After CO2 removal, the global MA is largely reduced below the present‐day state, as MA decreases over several monsoon regions. Further, when we compare MA at the same global warming level in CO2 ramp‐up and ramp‐down periods, many individual monsoon regions show reduced MA during the ramp‐down period. As MA is defined based on local contrast of summer and winter precipitation, we investigate hemispheric summer and winter precipitation responses and how they affect MA. The regional changes in MA are found to be due to distinct variations of local summer or winter precipitation, which are commonly associated with large‐scale atmospheric and oceanic variations. Further impacts of changes in MA with CO2 removal on the hydrological cycle more generally, are identified. Key Points: Non‐linear responses in global and regional monsoon areas to CO2 pathway are investigated using a coupled climate modelDistinct hysteresis in monsoon area variation is identified over global to regional monsoons between CO2 ramp‐up and ramp‐down periodThe hysteresis emerges due to distinct precipitation changes with large‐scale atmospheric and oceanic responses [ABSTRACT FROM AUTHOR]

Stable water isotopes are natural tracers in the hydrological cycle and have been applied in hydrology, atmospheric science, ecology, and paleoclimatology. However, the factors controlling the isotopic distribution, both at spatial and temporal scales, are debated in low and middle latitude regions, due to the significant influence of large-scale atmospheric circulation and complex sources of water vapor. For the first time, we made in situ observations of near-surface vapor isotopes over a large region (over 10 000 km) across China in both pre-monsoon and monsoon seasons, using a newly designed vehicle-based vapor isotope monitoring system. Combined with daily and multiyear monthly mean outputs from the isotope-incorporated global spectral model (Iso-GSM) and infrared atmospheric sounding interferometer (IASI) satellite to calculate the relative contribution, we found that the observed spatial variations in both periods represent mainly seasonal mean spatial variations, but are influenced by more significant synoptic-scale variations during the monsoon period. The spatial variations of vapor δ18 O are mainly controlled by Rayleigh distillation along air mass trajectories during the pre-monsoon period, but are significantly influenced by different moisture sources, continental recycling processes, and convection during moisture transport in the monsoon period. Thus, the North–South gradient observed during the pre-monsoon period is counteracted during the monsoon period. The seasonal variation of vapor δ18 O reflects the influence of the summer monsoon convective precipitation in southern China and a dependence on temperature in the North. The spatial and seasonal variations in d-excess reflect the different moisture sources and the influence of continental recycling. Iso-GSM successfully captures the spatial distribution of vapor δ18 O during the pre-monsoon period, but the performance is weaker during the monsoon period, maybe due to the underestimation of local or short-term high-frequency synoptic variations. These results provide an overview of the spatial distribution and seasonal variability of water isotopic composition in East Asia and their controlling factors, and they emphasize the need to interpret proxy records in the context of the regional system. [ABSTRACT FROM AUTHOR]

Precipitation change is critical for the Three-River Headwaters (TRH) region, which serves downstream communities in East Asia. The spring (March–May) precipitation over the TRH region shows an increasing trend from 1979 to 2018, as revealed by a Chinese gridded precipitation product (CN05.1). However, the physical processes responsible for this precipitation change are still unclear. This study investigated the characteristics of spring precipitation and the water budget over the TRH region using the ERA5 global reanalysis and the Weather Research and Forecast (WRF) Model. The WRF version employed in this study includes online calculations of the atmospheric water budget and an evapotranspiration (ET) tagging procedure to trace evapotranspired water in the atmosphere. Both ERA5 and WRF reproduce the spring precipitation increase. Moreover, WRFD02 (with a 3-km domain) reduces the wet bias by around 60% and 77% compared to WRFD01 (9 km) and ERA5 (30 km). Both ERA5 and WRF demonstrate that the increase of spring precipitation is dominated by moisture convergence, especially the atmospheric water fluxes from the southern boundary. The enhanced moisture inflow is sustained by enhanced mass flux while the enhanced moisture outflow is sustained by increased moisture. The ET-tagging results further demonstrate the weakened precipitation recycling process because of the significant increase of precipitation produced by external moisture. Compared to ERA5, the reduced wet bias with WRF is attributed to a better spatial resolution of orographic barrier effects, which reduce the southerly water fluxes. The results highlight the potential of regional climate downscaling to better represent the atmospheric water budget in complex terrain. [ABSTRACT FROM AUTHOR]

Pliocene warmth has been used as an analogue for predicting climate response to the rapid atmospheric CO2 increase in the future. Pedogenic carbonates provide an essential archive to reconstruct terrestrial paleoenvironment in a warm world. The stable carbon isotopic compositions of pedogenic carbonate ( δ 13 C carb ) are principally used to reconstruct the history of C4 plants along with coexisting organic matter δ 13 C SOM . However, a growing body of evidence shows spatial and temporal decoupling between δ 13 C carb and δ 13 C SOM especially in arid regions, raising concerns when using δ 13 C carb as a proxy for photosynthetic pathway. Here, we report paired δ 13 C carb and δ 13 C SOM data from Pliocene to early Pleistocene loess-paleosols in Chinese Loess Plateau (CLP), middle latitude East Asia. The model sensitivity analysis suggests the dominant control of soil respiration flux (SRF) on δ 13 C carb values in this region. SRF is then reconstructed using the Monte Carlo simulation method. Our results show that the SRF was enhanced during Pliocene warmth, associated with increased vegetation density and East Asian Summer Monsoon (EASM) precipitation. An overall higher SRF across the CLP during the mid-Pliocene, compared with the Holocene and Last Glacial Maximum (LGM) period, suggests there was a northwestward shift of the EASM rain belt and vegetation under warmer climate. Our results suggest that global temperature has dominated the middle latitude ecosystem and soil variations through its influence on the hydrological cycle, providing insights into future ecological and environmental response to global warming in East Asia. [ABSTRACT FROM AUTHOR]

Atmospheric rivers (ARs) are increasingly recognized as a major driver of hydrological cycles, and are projected to increase around the world under a changing climate. However, the long‐term trends of ARs over East Asia (EA) remains less elucidated. Here we fill the gap by developing a longest‐ever archive of EA ARs, and examine its role in determining spatiotemporal precipitation variability over EA. We find contrasting changes in AR occurrences, with more frequent ARs in low latitudes but less in high latitudes during the period 1950–2020. The "dipole" pattern of decadal changes in AR occurrences is dictated by atmospheric dynamics (i.e., winds) in the north but thermodynamics (i.e., moisture) in the south. The reduced AR occurrences explain 49% of decreased annual precipitation in northern China, while more AR‐related precipitation is observed in southern China. Our results provide new insights into regional hydroclimate over EA by connecting it with large‐scale weather systems. Plain Language Summary: Atmospheric rivers (ARs) feature long and narrow filaments with intense moisture transport in the lower troposphere. It is a vital component in the regional and global hydroclimate. Previous studies have documented the characteristics of ARs at both regional and global scales. However, studies about the mechanism of long‐term trends and its contribution to precipitation changes are still lacking. Here we examine the annual variation of ARs and its impacts on regional hydroclimate over East Asia. Our analysis is based on a long‐term, high‐resolution reanalysis data set. We show distinct spatial patterns of the changes in annual AR occurrences, with more ARs in low latitudes but decreased frequency in high latitudes. The "dipole" pattern is mainly related to wind changes in the north but moisture changes in the south. The reduced annual AR occurrences in high latitudes explain 49% of decreased annual precipitation in northern China, while more AR‐related precipitation is expected in southern China. The dipole‐like pattern of AR changes provides a good elucidation of the "Southern‐Flood and Northern‐Drought" pattern for East China. Key Points: The mean annual occurrences of atmospheric rivers (ARs) show increases in low latitudes but decreases in high latitudes over East AsiaThe "dipole" pattern of long‐term AR trends is associated with contrasting dynamic and thermodynamic responsesSuch changes in annual AR occurrences contribute to the "Southern‐Flood Northern‐Drought" precipitation pattern over eastern China [ABSTRACT FROM AUTHOR]

Previous studies have shown that Saharan dust can be transported thousands of miles, affecting regional climates, environments, and ecosystems. However, research on the long‐range transport of Saharan dust in Asia remains limited. We systematically investigated the long‐range transportation of Saharan dust over East Asia from 2007 to 2020 using WRF‐Chem model simulations, space‐borne CALIPSO lidar observations, NCEP/NCAR reanalysis data, as well as HYSPLIT trajectory analysis. The results show that one quarter (24.3 ± 6.2%) of dust events in East Asia during 2007–2020 originated from the Sahara Desert. Moreover, long‐range transported Saharan dust over East Asia was usually distributed in the upper troposphere. The average total amount of transported Saharan dust over East Asia between 2010 and 2015 was estimated at 33.05 ± 9.78 Tg/yr. Additionally, Saharan dust could be transported eastward all year and contributed about 35.8% of dust loading in the upper troposphere in Northern China in spring, which is almost the same amount of dust aerosols lifted up from East Asian dust sources. This study provides new sights on the important role of Saharan dust over East Asia, and elucidates the influence of long‐range transported dust on regional climate and the water cycle. Key Points: About one fourth of dust cases in East Asia from 2007 to 2020 originated from the Sahara DesertLong‐range transported Saharan dust over East Asia was usually distributed in the upper troposphere where is >5 km above sea levelOver East Asia, Saharan dust contributes 35.8% of total dust concentration in the upper troposphere in spring [ABSTRACT FROM AUTHOR]

• First sub-orbital scale hydrological record of PETM in East Asia. • Eccentricity forcing coincides with multi-phased precipitation variability. • Precession and half-precession cycles control precipitation intensity. • Orbital forcing of low-latitude insolation develops in East Asia during the PETM. The Paleocene-Eocene Thermal Maximum (PETM, ∼56 Ma) was an abrupt global warming event linked to massive carbon release into the ocean-atmosphere system. As such, it is considered a potentially useful analogue for present and future climate change. Consequently, deciphering its impact on the hydroclimate is important for predicting future changes under high p CO 2 and temperature conditions, especially in East Asia where more than a quarter of the world's population lives. Here, we use magnetic and geochemical data obtained through a thick lacustrine record of the PETM from China to demonstrate a large-scale increase in weathering and precipitation coeval with the PETM. Moreover, we show that precipitation variations through the PETM were strongly controlled by eccentricity, precession and half-precession climate cycles. Our results show that orbital forcing of low-latitude insolation played a key role in driving hydroclimate fluctuations and multi-phase changes in precipitation during the PETM, emphasizing the sensitivity of East Asian hydroclimate to subtle changes in insolation under conditions of high temperature and p CO 2 , perhaps similar to those expected in the future. [ABSTRACT FROM AUTHOR]

Recent decades have shown significant changes to the hydrological cycle over East Asia (EA), and further changes are expected due to future global warming. This study evaluates projected seasonal changes in the EA hydrological cycle using simulations that are 1.5 °C, 2.0 °C and 3.0 ∘ C warmer than pre-industrial, from the Met Office Unified Model (MetUM) Global Ocean Mixed Layer model version 2.0 (GOML2.0), compared against present-day conditions. The moisture sources of the warming-induced precipitation changes are identified over five hydrologically unique regions within EA. Precipitation over EA increases with warming (except over southeastern EA in the spring and autumn) due to the intensified hydrological cycle. The projected seasonal changes in the hydrological cycle are usually nonlinear, with the rate of change between 1.5 ∘ C and 2.0 ∘ C larger than the rate of change between 2.0 ∘ C and 3.0 ∘ C of warming. The warming-induced precipitation increases are mainly associated with an increase in remote moisture convergence rather than local moisture recycling, except over the Tibetan Plateau. Decomposition of the changes in moisture sources by direction and flux component indicate that changes from the west are dominated by changes to moisture and changes from the north are more circulation driven. The changes from the south are moisture driven over southern EA and driven by moisture and circulation change over northern EA. Our results highlight the regionally and seasonally diverse projected changes to the EA hydrological cycle due to global warming, which will be useful for region-specific climate mitigation policies and the implementation of seasonally varying adaptation methods. [ABSTRACT FROM AUTHOR]

Climate model simulations have suggested that, in East Asia, the mean precipitation increases with global warming, leading to more humid conditions. In contrast, Cretaceous proxy data show an aridification in the low latitudes of East Asia during the mid‐Cretaceous when CO2 levels were higher and the climate was relatively warmer compared to the early and late Cretaceous. We conducted simulations of the Present‐day and Cretaceous climates with different CO2 levels using an atmosphere‐ocean general circulation model, MIROC4m, to investigate the hydrological cycle changes as CO2 is increased. The results show that the responses of the hydrological cycle in East Asia for the Present‐day and Cretaceous experiments are the exact opposite; an increase in the Present‐day, and a decrease in the Cretaceous, as geological evidence shows. Overall, the opposite response in the Cretaceous is attributed to a weaker summer atmospheric circulation, associated with the absence of the Tibetan Plateau. Plain Language Summary: Projections indicate future global warming and an increase in the annual and summer mean precipitations and humidity around East Asia. On the other hand, geological records have shown the low‐latitude regions of East Asia during the warmer mid‐Cretaceous shifted toward more arid conditions, relative to the cooler early and late Cretaceous. We simulate the Present‐day and Cretaceous climates with different CO2 levels using a climate model, to investigate and compare the water cycle responses to global warming in the two periods. With increased atmospheric CO2, the precipitation in the low latitude regions of East Asia decreases in the Cretaceous experiment, consistent with changes in the water cycle during the mid‐Cretaceous as indicated by geological data, while it increases in the Present‐day experiment. It is found that this difference is caused by the different summer atmospheric circulation response due to the absence of the Tibetan Plateau in the Cretaceous. In conclusion, this study highlights that the regional changes in the hydrological cycle due to climate warming are strongly dependent on background geographical conditions. Key Points: Changes in the hydrological cycle during the Cretaceous are simulated by the MIROC4m climate model and are in agreement with proxy dataIn East Asia, the rainfall increases with global warming for Present‐day conditions, while it decreases for the CretaceousThe Tibetan Plateau determines the sign of the rainfall change in East Asia with global warming [ABSTRACT FROM AUTHOR]

• Large-scale TWS assimilation improves model performance. • Data assimilation captures negative trends in TWS, soil moisture, and ET. • Anthropogenic contribution to TWS trend marginally increases with assimilation. Terrestrial water storage (TWS) encompasses various components such as snow water, surface water, canopy water, soil water, and groundwater. Therefore, TWS is strongly affected by several factors including climate change, floods, drought, and anthropogenic activities. Predicting and quantifying TWS is critical in understanding terrestrial water cycles, as well as for managing water resources at the regional and global scale. TWS can be monitored with the Gravity Recovery and Climate Experiment (GRACE) satellites and estimated using land surface models (LSMs) on various spatial scales. The present study demonstrated how large-scale TWS data assimilation affects model performance by assessing the variations in TWS and related hydrological variables. Moreover, unlike traditional physical-based models, the assimilation of TWS data into an LSM enabled the assessment of anthropogenic impacts. TWS data from GRACE was assimilated into the Community Land Model version 5 (CLM5) with the CLM5-BGC biogeochemistry module covering the East Asia region. The model was forced using 40-ensemble meteorological forcing data from 2003 to 2010 and GRACE TWS data were assimilated using the ensemble adjustment Kalman filter (EAKF). Data assimilation markedly improved the performance of the model, as demonstrated by a decrease in the root mean square error from 0.71 mm/month in the free run (FR) without data assimilation to 0.48 mm/month in the data assimilation (DA) run, in addition to an increase in the correlation coefficient from 0.55 in FR to 0.69 in DA. Additionally, unlike the FR model, the DA model effectively captured the observed negative trends of the TWS, soil moisture, and evapotranspiration in Northern India and the Northern China Plain. Finally, our findings also demonstrated that the anthropogenic contribution to the negative trend of the TWS over Northern India and Northern China Plain was marginally increased in the DA model compared to the FR model. Collectively, our findings demonstrated that TWS data assimilation enables a more realistic evaluation of the long-term and large-scale changes in hydrologic variables. [ABSTRACT FROM AUTHOR]

Water vapor is the material basis of precipitation and an important component of the global hydrological cycle. Quantifying the contributions of terrestrial and oceanic moisture sources is crucial for comprehending regional precipitation and hydroclimate changes. Previous studies have extensively investigated the East Asian summer monsoon and its precipitation changes using geological climate records, but it remains unclear how water vapor from different source regions affects the orbital-scale precipitation change in East Asia. In this study, a long-term transient simulation using a climate model with a water-tagging scheme was conducted for the past 300 kyr to explore the contributions of terrestrial and oceanic moisture sources to precipitation changes in the northern East Asian monsoon region (NEA, 35–45°N, 105–120°E). The results showed that for the climatologically annual NEA precipitation, the global land source was the primary moisture source, accounting for approximately 57.6% of the total precipitation, followed by Pacific Ocean source contributing 20.9%, while other sources had a minor contribution. The orbital-scale changes of annual NEA precipitation, dominated by the precipitation of the rainy season from May to September, were mainly characterized by a significant 23-kyr cycle and a weak 100-kyr cycle. Analyses of water vapor sources found that the significant 23-kyr cycle in NEA precipitation was caused by the superposition of the synchronous 23-kyr cycles of precipitations from the land and Pacific Ocean sources, while the nonsynchronous 100-kyr cyclic changes of precipitations from the land and Pacific Ocean sources led to the weak 100-kyr cycle of NEA total precipitation. Further analysis of water vapor flux showed that the orbital-scale NEA precipitation changes were mainly controlled by the precession-induced Northern Hemisphere summer insolation variations, while changes in the global ice volume also had a certain modulation effect on NEA precipitation by regulating the contribution rates of land and Pacific moisture sources. This study highlights the importance of terrestrial and oceanic moisture sources associated with external forcings in understanding the orbital-scale East Asian monsoon precipitation changes. • Transient simulation of moisture tracking over the past 300 kyr was conducted. • Major moisture sources for precipitation over the northern East Asia were identified. • Contributions of moisture from land and Pacific sources were in antiphase at 23-kyr and 100-kyr cycles. [ABSTRACT FROM AUTHOR]

The understanding of the relationship between the variation of precipitation stable oxygen isotope ratio (δ18O p) and monsoon activity in the Asian monsoon region is crucial for an in-depth comprehension of the regional hydrological cycle processes and for reconstructing the history of Asian paleomonsoon changes. Based on the 1979–2017 summer δ18O p output by two isotope-enabled atmospheric general circulation models nudged to climate reanalysis data, this study explores the associations of the Indian summer monsoon (IM) and western North Pacific summer monsoon (WNPM) intensities with the interannual variations of the regional δ18O p and their possible physical mechanisms. Statistical analyses demonstrate that the East Asian δ18O p is negatively correlated with the IM intensity while the Indian δ18O p is positively correlated with the WNPM intensity. Moreover, the underlying mechanisms linking the monsoon and δ18O p vary in different regions. In strong IM years, with the intensified convection and increased precipitation near the Indian peninsula, the water vapor isotope ratio (δ18O v) transported to East Asia has lower values, resulting in the depletion of δ18O p there. The opposite is true for weak IM years. In years of strong WNPM, the intensified convection over the tropical western Pacific and the suppressed convection over the western Indian Ocean may be linked to a Walker-type circulation anomaly, accompanied by the enlarging of the vertical wind shear between the western Pacific and the western Indian Ocean. Accordingly, the decreasing of convection and precipitation over the Arabian Sea results in higher δ18O v values in the upstream area of India, which ultimately increases δ18O p values in the Indian peninsula through the monsoonal moisture transport; and vice versa. • East Asian summer δ18O p is negatively correlated with the Indian monsoon intensity. • Indian δ18O p is positively correlated with western North Pacific monsoon intensity. • East Asian summer δ18O p is regulated by the upstream depletion. • Indian δ18O p links to western Pacific convection through Walker-type circulation. [ABSTRACT FROM AUTHOR]

Known as the "third pole" and "water tower of Asia", the Tibetan Plateau (TP) is the home to the largest number of glaciers in the mid-latitudes and one of the most sensitive areas to global climate change due to its special geographical location and powerful thermodynamic effects. In recent years, the TP has been affected by exogenous pollutants and the concentrations of some pollutants have shown an increasing trend, especially light-absorbing aerosols (LAAs), when ice core records, ground- and aircraft-based field campaigns and satellite technology enabled synthesized monitoring. The enhanced warming of the vast majority of regions in TP, together with Arctic warming, and snow/ice decline, represents credible evidence of anthropogenic climate change. This paper provides a comprehensive review of studies on the sources, characteristics and climate impacts of LAAs over the TP. Adjacent to the two major emission sources of LAAs in East Asia and South Asia, the unique geographical location and climatic characteristics of the TP make it possible for TP LAAs to cause atmospheric warming and accelerated glacier melting, affecting the hydrological cycle in South Asia, East Asia and even the Northern Hemisphere, thus causing a series of serious environmental and social problems. LAAs, such as black carbon and dust, can strongly absorb solar radiation and and have significantly influence on climate change. Moreover, light-absorbing impurities (LAIs) on snow/ice can reduce the snow/ice albedo and further accelerate the snow/ice melting. Both LAAs and LAIs over the TP can induce thermodynamic feedback processes, cause significant warming of the TP and then lead to a strengthening of the early monsoon and affect the subsequent evolution of the monsoon. Many mechanisms have been proposed forth regarding how TP LAAs modulate the phase, intensity, and amplitude of the Asian climate system. A wide range of theoretical, observational, and modeling findings on TP LAAs and their climate impacts are synthesized, in which dust aerosols from drylands and black carbon from biomass burning are considered leading components. By coupling an integrated approach with state-of-the-art modeling, high temporal and fine spatial resolution remote sensing observations with increasing sampling over the TP will provide further insights into TP aerosols. • Light-absorbing aerosols warm the Tibetan Plateau, further influence climate system • The external input of light-absorbing aerosols over the Tibetan Plateau is dominant • Climate effects of light-absorbing aerosols or impurities in snow is divergent [ABSTRACT FROM AUTHOR]

The Songliao Basin (SLB) in Northeast China has a succession of terrestrial sedimentary deposits that span much of the Cretaceous. The sedimentary records recovered from SLB allow us to investigate the relationship between astronomically forced climate and clastic sediment accumulation in a terrestrial setting from the mid to high latitudes. Here, we compiled high-resolution X-Ray Fluorescence (XRF) datasets (K/Ti, Rb/Sr, Ca/Ti), and gamma ray (GR) logging data from Member 2 of the Nenjiang Formation in the SK-1n borehole. Power spectral analysis of the GR data revealed that sedimentary cycles had wavelengths of 27.4 m, 6.56 m, 2.60 m, and 1.27 m. These wavelengths are interpreted as the orbital cycles of long-eccentricity, short-eccentricity, obliquity, and precession, respectively. We established an astronomical time scale by assuming that the 27.4 m cycles represent ~405 kyr eccentricity. We also applied correlation coefficient (COCO) analysis to identify the astronomical forcing periods. The chemical weathering history was classified by the relative changes of Rb/Sr and K/Ti ratios. The lower Rb/Sr and higher K/Ti values correspond to weak weathering, interpreted as arid periods, and vice versa. Ca/Ti ratios correlate with the humid periods and we attribute this correspondence to a salinity control on Ca/Ti. Furthermore, the unconventional 173-kyr obliquity cycle associated with the secular frequency interference of orbital inclinations between Earth and Saturn was recognized and manifested by humid/arid cliamtic oscillations, suggesting that high obliquity contributed to strengthening the hydrological cycles in SLB and bringing more precipitation and runoff towards the basin. The unique paleogeographic location and the existing paleoclimate simulations of SLB further demonstrated the existence of paleomonsoon variations in East Asia during the Late Cretaceous. • Sedimentation rate from 5.1 to 8.3 cm/kyr was simulated by three proxies. • The chemical weathering suggested humid-arid changes related to the paleomonsoon. • The ~173 kyr cycle was recognized and associated with the humid-arid changes. • High obliquity contributes to strengthening the hydrological cycles in Songliao Basin. [ABSTRACT FROM AUTHOR]

Clouds play a significant role in the climate system, which affects the radiation balance and modulates the global hydrological cycle. However, the existing cloud property products have poor spatiotemporal continuity with only daytime cloud property retrieval results, which makes it challenging for us to carry out researches related to clouds at night. In this study, the effect of parallax error between the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and Himawari-8 data is corrected based on parallax correction algorithm by referring to cloud parameters extracted from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) cloud property product. Due to the different sensitivity of different channels to clouds, this study treats the CALIOP data with cloud optical depth greater than 0.2 as clouds, otherwise as clear sky. Cloud property retrieval model based on the XGBoost machine learning (ML) algorithm is developed for the advanced Himawari imager (AHI) onboard the Himawari-8 satellite. The ML model can achieve unified cloud mask, cloud top temperature (CTT), and cloud top height (CTH) retrieval for both daytime and nighttime with high spatial (0.02°) and temporal (10 min) resolutions using the AHI thermal data. The retrieval results are extensively evaluated over study regions (80° E ~ 135° E, 18° N ~ 55° N) by comparisons with cloud property products of JAXA (Japan Aerospace Exploration Agency) AHI, MODIS, and CALIOP data. The ML algorithm has higher cloud detection accuracy with cloudy sky (clear sky) hit rate (CHR) and false alarm rate (FAR) of 90.79% (88.35%) and 5.74% (4.67%) compared with the JAXA AHI (CHR = 92.81% (60.64%) and FAR = 19.66% (3.61%)) and MODIS (CHR = 88.50% (72.32%) and FAR = 13.10% (6.06%)) cloud products, and the ML algorithm also performs well for thin clouds over bright surfaces. The CTH and CTT retrieved by the ML algorithm (RMSE = 1.83 km and 12.29 K) are in good agreement with the CALIOP cloud property product, and the root mean squared error (RMSE) of CTH and CTT is reduced by 33.70% (18.67%) and 35.28% (16.45%) on average, respectively, compared with the JAXA AHI (MODIS) cloud product with RMSE of 2.76 km (2.25 km) and 18.99 K (14.71 K). In addition, the ML algorithm can obtain higher cloud property retrieval accuracy at night compared with the results during the day. • Machine learning (ML) based retrieval model is developed for AHI cloud retrieval. • The ML model can achieve cloud mask, CTT, and CTH for both day and night time. • The ML cloud detection accuracy is larger than that of JAXA AHI (MODIS) product. • The CTH RMSE decreased by 33.70% (18.67%) compared to the JAXA AHI (MODIS) product. • The CTT RMSE decreased by 35.28% (16.45%) compared to the JAXA AHI (MODIS) product. [ABSTRACT FROM AUTHOR]

The Heinrich Stadial (HS) 4 event was the largest of the six HS events and occurred from 40.0 to 38.2 kyr BP (thousand years before present, where present = 1950 CE) recorded in Greenland ice cores. However, its structure, forcings, and related global hydroclimate variation remain poorly understood. Here, an 8-yr-resolved stalagmite δ18O record from Xianyun Cave, southeastern China, is used to reconstruct the multidecadal-to-millennial-scale changes of the East Asian summer monsoon (EASM) from 41.33 ± 0.09 to 37.04 ± 0.05 kyr BP. The Xianyun record shows a corresponding weak monsoon interval from 40.04 ± 0.07 to 37.76 ± 0.05 kyr BP during HS 4 and is the first direct evidence in the Asian monsoon realm to clearly reveal a three-phase EASM structure. The first phase began with a weakening monsoon from 40.04 ± 0.07 to 39.54 ± 0.06 kyr BP, associated with a southward shift of the Intertropical Convergence Zone (ITCZ). The second phase was a long weak monsoon, spanning 1.06 kyr from 39.54 ± 0.06 to 38.48 ± 0.05 kyr BP and corresponding to an ice-rafted debris event in the North Atlantic Ocean and an intense pluvial phase in Northeast (NE) Brazil, suggesting that the ITCZ lingered at its southernmost position during this interval. Following the end of this phase, EASM was gradually enhanced for 720 yrs through 37.76 ± 0.05 kyr BP. The feature expressed in the Xianyun record agrees with the variations in low-latitude climate signals recorded in the Northern Greenland Eemian Ice Drilling (NEEM) 17O-excess and anti-phase matches with dry-wet transition recorded in NE Brazilian stalagmites. These relations suggest multi-phased responses of tropical atmospheric/oceanic circulations to forcing from northern hemisphere high latitudes. Our findings offer essential evidence for understanding low- and high-latitude climate teleconnections and the relationship between the monsoon and the tropical hydrologic cycle. • An 8-yr-resolved δ18O stalagmite record from Xianyun Cave shows the EASM history from 41.3 to 37.0 kyr BP. • The revealed three-phase EASM evolution is from 40.0 to 37.8 kyr BP during the Heinrich Stadial 4 event. • The gradual 500-yr onset and 720-yr termination of the weak EASM were modulated by tropical hydroclimate. [ABSTRACT FROM AUTHOR]

A better understanding of the water and energy cycles at climate scale in the Third Pole Environment is essential for assessing and understanding the causes of changes in the cryosphere and hydrosphere in relation to changes of plateau atmosphere in the Asian monsoon system and for predicting the possible changes in water resources in South and East Asia. This paper reports the following results: (1) A platform of in situ observation stations is briefly described for quantifying the interactions in hydrosphere-pedosphere-atmosphere-cryosphere-biosphere over the Tibetan Plateau. (2) A multiyear in situ L-Band microwave radiometry of land surface processes is used to develop a new microwave radiative transfer modeling system. This new system improves the modeling of brightness temperature in both horizontal and vertical polarization. (3) A multiyear (2001–2018) monthly terrestrial actual evapotranspiration and its spatial distribution on the Tibetan Plateau is generated using the surface energy balance system (SEBS) forced by a combination of meteorological and satellite data. (4) A comparison of four large scale soil moisture products to in situ measurements is presented. (5) The trajectory of water vapor transport in the canyon area of Southeast Tibet in different seasons is analyzed, and (6) the vertical water vapor exchange between the upper troposphere and the lower stratosphere in different seasons is presented. [ABSTRACT FROM AUTHOR]