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Following the description of the basic climatic characteristics of Meiyu in East Asia, we present a comprehensive review of multi–time scale variabilities of the Meiyu together with the long‐term change of extreme precipitation during the Meiyu in this paper. The dynamic prediction skills of the Meiyu on subseasonal to seasonal time scales are further described and illustrated by using present numerical prediction models. For the multi–time scale variabilities of the East Asian Meiyu, they are closely related with the impacts of both quasi‐biweekly and 30–60 day oscillation from both the tropics and the middle and high latitudes on intraseasonal time scale, the influences of El Niño–Southern Oscillation and the Tropospheric Biennial Oscillation on interannual time scale, the variations of East Asian summer monsoon on decadal time scale, and the continued impacts of global warming, Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation on interdecadal scale and long‐term trend. Under the background of the global warming and the influences of urbanization and aerosol effects, the Meiyu shows some specific characteristics including significantly weakened continuous rain, uneven spatial distribution of precipitation, and increased (decreased) number of strong (weak) precipitation days. Improvements of prediction on rain belt location, total precipitation amount, persistent heavy precipitation events, and low‐frequency variability oscillation during Meiyu season have been achieved with the improved dynamic models of the Beijing Climate Center since 2010. Key Points: Meiyu's variabilities are related with intraseasonal oscillation, interannual to multidecadal oscillation of ocean, and global warmingMeiyu impacted by global warming, urbanization, and aerosol effects exhibits stronger rainfall eventsImprovements of prediction of East Asian Meiyu on multi‐time scale have been achieved with the present operational climate models [ABSTRACT FROM AUTHOR]

In this study, we developed a regional coupled model for the western North Pacific (WNP) and East Asian region. The atmospheric/oceanic component of the coupled model was the Weather Research and Forecasting and the Regional Ocean Modeling System, coupled through the National Center for Atmospheric Research Coupler version 7 (CPL7). An evaluation is provided through the simulation of the climatology and interannual variability of the summer monsoon climate from 1982 to 2015. The coupled model is also compared with a solely atmospheric run, which is driven by the observed sea surface temperature (SST) as the surface boundary. The results show that the coupled model has good capability in modeling the climate in the WNP and East Asian domain, including the climatology of summer precipitation and circulation, the subseasonal (month‐to‐month) variation in the western Pacific subtropical high and associated precipitation, and the seasonal cycle of the East Asian rain belt. One merit of this model is its ability to simulate the northward and eastward shift from early to late summer. With respect to the interannual variability, the model captures the spatial pattern of the leading mode of summer precipitation, with a north–south dipole mode in the studied region. The model also reproduces the larger SST variability in the northern part of this region. The temporal correlation coefficient between the coupled simulation and observation was 0.70 for the precipitation and 0.53 for the SST leading mode. The coupled model also captures the precipitation–SST relationship, which results from reasonably considering the air–sea coupling processes in the coupled run. Plain Language Summary: Due to the resolution of global models is relatively coarse and cannot describe the regional features, especially in the monsoon regions, regional climate model is an essential solution for regional climate simulation and projection. Compared with atmospheric alone model which is driven by prescribed sea surface temperature, regional air‐sea coupled model can describe reasonably the air‐sea coupling processes and has better performance. In this study, an regional coupled model is developed based on the Community Earth System Model coupler version 7 framework. Based on our analysis, the regional coupled model reasonably reproduced most key characteristics in the East Asian monsoon region. In addition to being used in regional climate simulation and projection, it can also be conveniently coupled with global models through the coupler 7. Thus with this useful tool in future we can develop global‐regional two‐way coupling simulation system for climate predictions and projections. Key Points: A regional coupled model is developed for East Asia and western North Pacific region based on Community Earth System Model frameworkClimatology and interannual variability of the summer monsoon climate have been evaluatedThe model can well capture the climatological northward and eastward movements of the western Pacific subtropical high from June to August [ABSTRACT FROM AUTHOR]

Drought is a recurring challenge, especially in the arid and semi‐arid regions. Therefore, understanding its spatial and temporal variation is important for pre‐disaster planning and sustainable water resource management during drought. However, the sparse and short length of the instrumental records in midlatitude East Asia hampered the full understanding of drought variation, especially at multidecadal and longer timescales. Here, we compiled a tree‐ring network of 364 chronologies in midlatitude East Asia and reconstructed the variation of the averaged May–August Standardized Precipitation Evapotranspiration Index at a spatial resolution of 0.5° × 0.5°, for the period 1501–2000 CE. The reconstruction captured the spatial and temporal variation of actual drought well and has a strong association with a drought atlas that was derived from historical documents. The study area has experienced an expansion of dry areas during the past decades; however, it is still within the natural variability of the past half millennium. According to drought variation during the instrumental period, the study area was divided into four subregions; however, running correlations showed that drought variation in some subregions was similar in past centuries, except in recent decades. This study provides new data for understanding the spatiotemporal variability of drought in midlatitude East Asia, and the vanished correlation between drought variation in some regions during the past decades indicates the complex forcing mechanism of regional drought variation. Plain Language Summary: We present a 500‐year drought reconstruction for midlatitude East Asia with a spatial resolution of 0.5° × 0.5°, by using a tree‐ring network of 364 chronologies. Based on this reconstruction, we found that the recent dry area expansion in midlatitude East Asia is still within the range of natural variability of the past 500 years. Our results also showed that, except for the past several decades, the drought variation in some subregions was significantly correlated. Key Points: We reconstructed drought variation of midlatitude East Asia over the past half millennium at a spatial resolution of 0.5°The recent drying and dry area expansion are within the range of natural variability of the reconstructionIn some regions, drought variations are currently uncorrelated, but have been similar in past centuries [ABSTRACT FROM AUTHOR]

Acting as efficient ice‐nucleating particles, dust particles can affect cirrus cloud properties through heterogeneous nucleation. A dust‐infused baroclinic storm (DIBS) over East Asia in May 2017 was examined using satellite observations and the Weather Research and Forecasting model coupled with chemistry (WRF‐Chem) to study the dust effects on cirrus clouds. Satellite observations showed that the ice number concentration (Nice) was extremely high, exceeding 1–10 cm−3 at the cirrus shield of the DIBS, and the ice effective radius (rei) was about 10–30 μm. An aerosol‐aware heterogeneous ice nucleation parameterization (Ullrich et al., 2017, https://doi.org/10.1175/jas-d-16-0074.1) was implemented into WRF‐Chem to explore the formation mechanism of such a high Nice. The simulated Nice from Ullrich17 was 1–2 orders of magnitude higher than that from the default scheme (Cooper, 1986, https://doi.org/10.1007/978-1-935704-17-1%5f4), and the rei was 2–3 times smaller. The results from Ullrich17 were more consistent with satellite observations, which can be attributed to the enhanced deposition nucleation from the high dust concentrations. Our results demonstrated that the extremely high Nice could be fully explained by the heterogeneous nucleation of dust particles in DIBS. A conceptual framework is proposed to explain the dust‐cloud interactions in DIBS. This study confirms the significant dust effects on cirrus clouds in DIBS and highlights the importance of using aerosol‐aware ice nucleation parameterizations in modeling cirrus clouds when the dust is present. Plain Language Summary: Cirrus clouds have a significant impact on the Earth's radiative budget and climate. Dust particles are efficient ice nucleating particles for enabling the ice formation process in cirrus clouds. We found extremely high ice number concentrations at the top cirrus shield of dust‐infused extratropical cyclone clouds using satellite observations. To understand how such high concentrations of ice crystals form, we implemented an aerosol‐aware ice nucleation parameterization into a regional chemistry‐climate model. The simulated ice number concentration and ice effective radius were significantly improved when using the newly added ice nucleation scheme. According to satellite observations and model results analysis, we proposed a conceptual framework for the formation mechanism of such high ice concentrations. Dust particles were transported to the altitude of the cirrus shield through the warm conveyor belt, and numerous ice crystals were formed from the deposition nucleation on dust particles with the consumption of water vapor. This study confirms the significant dust effects on cirrus shields in dust‐infused extratropical cyclone clouds. Future modeling work on cirrus clouds associated with dust should take the aerosol effects into account. Key Points: Extremely high concentrations of ice particles in dust‐infused baroclinic storm (DIBS) cirrus shield by the heterogeneous deposition nucleation of dust particles were foundThe importance of aerosol‐aware ice nucleation parameterizations in modeling dust‐cloud interactions within DIBS was demonstratedThe conceptual framework is proposed to explain the dust‐cloud interactions in DIBS [ABSTRACT FROM AUTHOR]

Long‐range U.S. summer rainfall prediction skill is low. Monsoon variability, especially over the West North Pacific Monsoon (WNPM) and/or East Asian Monsoon (EAM) region, can influence U.S. Great Plains hydroclimate variability via a forced Rossby wave response. Here, we explored subseasonal monsoon variability as a source of predictability for Great Plains rainfall. The boreal summer intraseasonal oscillation (BSISO) is related to Great Plains convection and Great Plains low‐level jet (LLJ) anomalies as well as a cross‐Pacific wave train. Using a causal effect network, we found that the time between BSISO‐related geopotential height anomalies and Great Plains rainfall anomalies is about 2 weeks; therefore, BSISO convection may be a valuable forecast of opportunity for subseasonal prediction of Great Plains convection anomalies. More specifically, causal link patterns/maps revealed that the above‐normal weekly EAM rainfall, rather than WNPM rainfall or general geopotential height activity over the East Asia, was causally linked to Great Plains LLJ strengthening and active Great Plains convection the following week. Plain Language Summary: Forecasting U.S. summer rainfall out past ∼7–10 days, considered the subseasonal timescale, is a challenge. However, there are times when subseasonal forecast skill is relatively higher due to propagating atmospheric waves from remote climate events. The West North Pacific Monsoon (WNPM) and East Asian Monsoon (EAM) can provide a remote influence via their related heating triggering atmospheric waves. Using an algorithm that effectively identifies and quantifies cause‐and‐effect relationships, we constructed a network that connects EAM rainfall and Great Plains rainfall via these atmospheric waves. We found that above‐normal EAM rainfall, rather than WNPM rainfall or general atmospheric wave activity over the East Asia, was causally linked to active Great Plains convection the following week. Therefore, monsoon variability, especially over the EAM region, might be a valuable source of subseasonal predictability for U.S. summer rainfall. Key Points: Subseasonal monsoon variability is linked to rainfall signals over U.S. Great Plains and its associated dynamical driversA cause‐and‐effect algorithm verified a pathway from regional monsoon rainfall to Great Plains rainfall, which takes approximately 2 weeksWeekly East Asian monsoon rainfall is causally linked to Rossby wave excitation and active Great Plains convection about 1 week later [ABSTRACT FROM AUTHOR]

Based on the normalized difference vegetation index (NDVI) and empirical orthogonal function analysis, a "northeast‐southwest" dipole pattern of spring vegetation in mid‐high latitude Asia was detected. This pattern was revealed to be associated with the autumn sea ice concentration (SIC) anomalies in the Barents‐Laptev Seas on the interannual variability. Increased autumn SIC over the Barents‐Laptev Seas tends to increase spring NDVI over the west of Lake Baikal and decrease spring NDVI in the Russian Far East. Further analyses indicated that the sea surface temperature (SST) anomalies persisting from winter to spring over the Northeast Atlantic and the Northwest Pacific play an important role in such a relationship. Increased autumn SIC over the Barents‐Laptev Seas is associated with a teleconnection pattern over the mid‐high latitudes in the following winter, accompanied by anomalous anticyclonic circulations over the Northeast Atlantic and the Northwest Pacific. Such changes in the large‐scale circulations induce downward net heat flux anomalies over the Northeast Atlantic and the Northwest Pacific, thereby contributing to the warming of SST which may persist to spring and in turn influence the atmospheric circulations. The Northeast Atlantic SST warming in spring may evoke a downstream wave train and cause positive geopotential height anomalies over the west of Lake Baikal, which increases local temperature and hence the vegetation. The Northwest Pacific SST warming in spring may lead to negative geopotential height anomalies over the Russian Far East through a meridional wave train, consequently resulting in a decrease in local temperature and hence vegetation. Plain Language Summary: The complex relationship between the climate and vegetation dynamics has been receiving a great deal of research attention. While much is known about how spring vegetation is controlled by the basic conditions such as temperature and precipitation, few studies have examined the response of the vegetation to Arctic sea ice. Our results reveal that the "northeast‐southwest" dipole pattern of spring vegetation in mid‐high latitude Asia is closely related to the preceding autumn sea ice concentration in the Barents‐Laptev Seas. The sea surface temperature anomalies persisting from winter to spring over the Northeast Atlantic and the Northwest Pacific play an important role in bridging such a relationship. These findings contribute to a better understanding of the change in spring vegetation over mid‐high latitude Asia. Key Points: A "northeast‐southwest" dipole pattern of spring vegetation is detected over mid‐high latitude AsiaThe spring vegetation dipole pattern is linked to the preceding autumn sea ice variation in the Barents‐Laptev SeasThe sea surface temperatures in the Northeast Atlantic and Northwest Pacific play an important role in bridging such a lag linkage [ABSTRACT FROM AUTHOR]

The impact of autumn Arctic sea ice reduction on the winter climate in Eurasia has been widely studied, but the role of the atmospheric circulation of the preceding summer has been mostly neglected. This study investigates a linkage between the summer Arctic circulation anomaly and the ensuing East Asian Winter Monsoon (EAWM) variability. The Arctic circulation anomaly, characterized by an anomalous anti‐cyclone occupying the Arctic Ocean and its marginal seas, can strongly melt Arctic sea ice in the Kara Sea‐Laptev Sea‐East Siberian Sea‐Chukchi Sea‐Beaufort Sea through dynamic and thermodynamic processes. The combination of the summer anti‐cyclone (cyclone) anomaly and light (heavy) autumn sea ice leads to an enhanced (weakened) EAWM. By introducing the coupling relationship between summer circulation and autumn sea ice into numerical experiments, the Community Atmospheric Model version 4 model has a good capability for capturing EAWM variability. Nevertheless, the dominant features of EAWM variability cannot be reproduced when the autumn sea ice mismatches the preceding summer circulation in the model. Therefore, the preceding summer circulation may modulate the impact of sea ice on Eurasia to some extent, which may increase uncertainties in the impact of Arctic sea ice loss on winter atmospheric circulation variability. Plain Language Summary: The enhanced East Asian Winter Monsoon (EAWM) leads to cold winter and has a significant impact on the economy, agriculture, and the lives of more than one billion people in East Asia, and the reduced autumn Arctic sea ice is generally believed to influence EAWM variability with great uncertainties due to strong atmospheric internal variability and impacts of other factors. In this study, through observational analysis and large ensemble model simulation experiments, a coupling relationship between the summer Arctic anti‐cyclone anomaly and the Arctic sea ice and their synergistic effect on EAWM variability are investigated. The summer anti‐cyclone anomaly over the Arctic corresponds to light sea ice and enhanced EAWM. Model experiments show that the summer initial conditions may modulate the lag impact of sea ice boundary conditions on winter circulation. Therefore, it is important to consider the synergistic effect of initial conditions and boundary conditions for predicting EAWM and winter surface temperature. Key Points: The Arctic anti‐cyclone (cyclone) anomaly in summer is a great predictor of the East Asian Winter Monsoon (EAWM)The combination of summer anti‐cyclone (cyclone) anomaly and light (heavy) autumn sea ice leads to an enhanced (weakened) EAWMFailure to consider the synergistic effect of initial conditions and sea ice may be one reason for the uncertainty of sea ice effect [ABSTRACT FROM AUTHOR]

Northeast China cold vortex (NECV) is the major influencing weather system in northern China. Yet the impacts of complex terrain on the evolution of NECV remains poorly understood. This work studies the influence of subgrid orographic drag (SOD) on a heavy‐rain‐producing NECV occurred in July 2011 using the Weather Research and Forecasting model. A series of numerical experiments are conducted with different parameterizations of SOD including turbulent orographic form drag (TOFD), flow blocking drag (FBD), and mountain wave drag (MWD). Results show that the NECV intensity is overestimated in the absence of SOD parameterization, accompanied with too‐low geopotential height (GPH) and too‐strong horizontal winds. The parameterization of TOFD can significantly decelerate the 10‐m winds, whereas the FBD and MWD play a minor role. However, the influence of TOFD is overwhelmed by FBD and MWD in the troposphere, especially the latter. This implies that the breaking of mountain waves play a more important role in weakening the NECV than the low‐level flow blocking. The lower‐tropospheric MWD directly weakens the convergence and ascent motion of the NECV, producing an anti‐cyclonic circulation that uplifts the GPH under the constraint of quasi‐geostrophic vertical vorticity. This MWD‐induced circulation indirectly weakens the NECV in the mid‐upper troposphere by producing a warm advection that counters the low‐level cold advection to the southwest of the NECV. The findings provide useful insights into the impacts of complex terrain on the NECV and highlight the importance of topographic drag parameterization in the simulation and short‐range forecast of NECV. Plain Language Summary: Northeast China cold vortex (NECV) is a major influencing weather system in northern China which often promotes severe convective weather like heavy rainfall, hail, and tornado. Past studies have revealed the importance of atmospheric circulations (e.g., Rossby waves associated with Eurasian blocking), sea surface temperature anomalies over North Pacific, and large‐scale orography in East Asia on the evolution of NECV. However, the underlying terrain in East Asia is much complex. It is still unclear how the NECV is affected by complex terrain. This work studies a NECV case using the Weather Research and Forecasting model, focusing on the impacts of different topographic drags including turbulent orographic form drag (TOFD), mountain wave drag (MWD), and flow blocking drag (FBD) produced by complex terrain. The influence of TOFD is basically confined in the boundary layer whereas the FBD and MWD play a major role in the troposphere, especially the latter. The low‐level MWD directly weakens the NECV in the lower troposphere by inducing an anti‐cyclonic circulation. Consequently, the low‐level cold advection to the southwest of the NECV is suppressed which indirectly weakens the NECV in the mid‐upper troposphere. The findings highlight the importance of topographic drag parameterization in the simulation and short‐range forecast of NECV. Key Points: The impacts of different topographic drag on the Northeast China cold vortex are firstly studied using numerical sensitivity experimentsTurbulent orographic form drag dominates the impact on near‐surface winds, while mountain wave drag plays a major role in the troposphereLow‐level mountain wave drag directly and indirectly weakens the cold vortex in the lower and mid‐upper troposphere, respectively [ABSTRACT FROM AUTHOR]

Understanding millennial‐scale East Asian summer monsoon (EASM) variability is critical for climate projection in East Asia in the context of slowing Atlantic Meridional Overturning Circulation (AMOC) caused by global warming. This study performs two groups of sensitivity experiments at 8.2 and 4.2 ka BP, both forced by the same North Atlantic freshwater hosing and corresponding orbital parameters using the Community Earth System Model, to explore the orbital effect on millennial‐scale EASM variability. Our simulations reveal that EASM variability differs significantly between these two cold events. During the 8.2 ka BP (4.2 ka BP) (0 BP = 1950 AD) cold event, North Atlantic freshwater forcing weakens the EASM, generating a meridional tripole (dipole) pattern of EASM precipitation anomalies. Furthermore, the same freshwater discharge causes a greater decline in the EASM, contrasting to a slight weaker AMOC slowdown, at 4.2 ka BP than at 8.2 ka BP. This suggests orbital parameters significantly influence the EASM response to North Atlantic cold events. The East Asian subtropical westerly jet, whose meridional position and intensity are controlled by summer insolation on an orbital timescale, plays a key role in this orbital effect. The westerly jet's meridional position determines the spatial pattern of EASM precipitation anomalies, while its intensity affects the amplitude of the EASM's response to freshwater forcing. Because of a larger EASM decline due to freshwater hosing with lower summer insolation, we anticipate a profound declining EASM precipitation in the future with low summer insolation if the AMOC continues to weaken. Key Points: Millennial‐scale East Asian summer monsoon (EASM) variability is modulated by Earth's orbital parametersThe EASM weakens more pronounced in response to North Atlantic freshwater forcing under lower summer insolationSummer insolation influences the EASM response to North Atlantic freshwater forcing via the westerly jet [ABSTRACT FROM AUTHOR]

In June‐July 2020, the Middle and Lower Yangtze River Region (MLYR) encountered the most severe precipitation event over the past 60 years. The Indian Ocean Dipole (IOD) in the previous autumn of the unusual precipitation event was the main contributing factor. Nonetheless, not every strong IOD event could bring anomalously high precipitation in the MLYR. This study showed significantly enhanced influence of IOD on East Asia climate since 2000. The IOD's effect on MLYR summer precipitation has strengthened significantly with the correlation coefficient up to 0.55 during 2000–2020. The northward movement of East Asia–Pacific pattern associated with IOD since 2000 (as compared with before) was primarily responsible for the enhanced effect. Since 2000, the MLYR has been controlled by a deep baroclinic instability system with anomalous low pressure in the lower troposphere and anomalous high pressure (completely different from before). Furthermore, the western Pacific subtropical high shifted northward and westerly jets were significantly enhanced with eastward expansion. All of these patterns contributed to the water vapor convergence and precipitation generation in the MLYR, which was not the case in the past. The record‐breaking IOD in 2019 autumn and the enhanced IOD's climatic effect in 2000–2020 contribute to the extreme Meiyu in 2020 jointly. The significant change in the influence of IOD and the enhanced climate effect of IOD highlight exciting new avenues for improving climate predictions in the MLYR. Plain Language Summary: The excessive Meiyu rainfall over the Middle and Lower Yangtze River Region (MLYR) during summer 2020 was beyond expectations of meteorologists, because in the 2019/20 winter, the Niño3.4 index was marginal at only 0.5°C as compared to 2.4°C and 2.6°C in 1997/98 and 2015/16 winters, respectively. Researches pointed out that the severely positive Indian Ocean Dipole (IOD) in the previous season was the main contributing factor on 2020 extreme Meiyu event in the MLYR. Nonetheless, not every strong IOD event could bring anomalously high precipitation in the MLYR. Our study shows significantly enhanced influence of IOD on East Asia climate since 2000. The IOD's effect on MLYR summer precipitation has strengthened significantly with the correlation coefficient up to 0.55 during 2000–2020. The IOD‐induced circulation patterns, including East Asia–Pacific pattern, the western Pacific subtropical high, and westerly jets, shifted northward with stronger intensity since 2000 (as compared with before). These results help us to reconsider the influence of tropical Indian Ocean sea surface temperature when forecasting weather or the possible climate changes under global warming. Key Points: The impact of Indian Ocean Dipole (IOD) on the Yangtze precipitation has enhanced in recent decadesThe IOD‐induced East Asia–Pacific pattern moves northward since 2000The interdecadal change in IOD's climatic effect largely contributes to the extreme Meiyu in 2020 [ABSTRACT FROM AUTHOR]

Regional air quality over East Asia, including South Korea, has recently become a center of public attention because of a few episodes of very high particulate matter (PM) concentrations. Predicting PM variation with lead time of a few hours up to days is one of the key areas that the governments are working on because it can benefit from an early warning system to short‐term mitigation effort. In this study, the influence of synoptic weather conditions on regional air quality was investigated with the occurrence frequencies of PM episodes as a function of various synoptic weather patterns during winter and spring. During winter, dry moderate (DM) types occur frequently alongside high PM cases (24 hr mean PM10 concentration >100μgm−3 $100\,{\upmu }\mathrm{g}{\mathrm{m}}^{-3}$). The composite weather map showed a weak northwesterly wind field as a potential cause. On the contrary, it is interesting to note that dry polar types can be associated with low PM cases (24 hr mean PM10 concentration <100μgm−3 $100\,{\upmu }\mathrm{g}{\mathrm{m}}^{-3}$) as well as high PM depending on near‐surface wind speed. Furthermore, DM and dry tropical types were found to be highly correlated with high (higher) PM concentrations during spring season, likely because of the enhanced static stability in the lower troposphere. It should be noted that PM concentration depends on the lower atmospheric stability. The close relationship between synoptic weather patterns and PM concentration suggests that synoptic weather can play an important role in regional air quality. Plain Language Summary: East Asia, including South Korea, has become a regional hot spot for the deteriorating air quality in recent years. In spite of the tough regulation policy introduced by the South Korean government, several high particulate matter (PM) episodes have still been reported. In this study, the relationship between the surface PM concentration and synoptic weather patterns over South Korea was investigated. A scientific basis for an early warning system and short‐term mitigation strategies was established. The near‐surface wind speed was likely a key variable during winter. On the contrary, atmospheric stagnant in the lower troposphere played an important role during spring season. The results indicate a close relationship between the synoptic weather patterns and surface PM concentration. Key Points: Several distinct synoptic weather patterns are highly associated with air quality degradation over South Korea during winter and springDuring winter, weak near‐surface northwesterly wind is a potential cause for high particulate matter (PM) under dry moderate (DM) types. On the other hand, during spring, enhanced stability in the lower atmosphere likely results in high PM in both DM and dry tropical typesInterestingly, the degree of PM concentration depends on the intensity of key weather variables such as wind speed and static stability in case of the same synoptic weather pattern [ABSTRACT FROM AUTHOR]

High‐temporal‐resolution geostationary satellite infrared measurements are always used to capture and predict typical characteristics at the cloud top of rapidly developing strong storms at the pre‐convection or convection initiation (CI) stage. However, the large false alarm rate of CI nowcasting is difficult to avoid due to the complex and unpredictable trigger factors. Although the microwave measurement technique can observe thick clouds and even the precipitation within clouds due to the weaker atmospheric extinction effect on microwave, microwave data from polar‐orbiting satellites are rarely used to observe the CI due to their relatively low temporal resolution. In this study, we analyze several previously unknown CI characteristics over the East Asia region from 2016 to 2019 based on spatially and temporally matched Advanced Technology Microwave Sounder data. These typical CI samples are initially identified by using continuous infrared images from the Himawari‐8 geostationary satellite. The results show that there is a distinct cloud optical depth at the pre‐convection stage in the western (deep cloud clusters) and eastern (shallow cloud clusters) Tibetan Plateau (TP). The shallow precipitating cloud clusters of the CI over the eastern TP are possibly attributed to the favorable local dynamic and thermal conditions stem from the Asian monsoon. Another notable finding shows that the fast‐developing CI over the ocean has thick clouds compared with the samples over the land. Overall, the unique CI characteristics found from microwave observations in this study indicate that the future geostationary microwave sounder technologies will almost certainly provide some new findings and enhance early warning capabilities about convection. Key Points: This study uses microwave sounder data to explore some previously unknown convection initiation (CI) characteristicsMore relatively shallow cloud clusters at the pre‐convection stage are found based on microwave observations in the eastern Tibetan PlateauCompared with the samples over the land, strong CI that develops rapidly over the ocean has thicker clouds [ABSTRACT FROM AUTHOR]

The intraseasonal meridional wave trains are the major features of East Asia summer monsoon (EASM), but the complete physical pictures of dynamic pathways from tropical and mid‐high latitudes and their climate impacts have not been fully illustrated. With NCEP‐DOE Reanalysis‐II daily data set, two boreal summer intraseasonal meridional oscillations (ISMOs) are isolated and identified by extended EOF of zonal wind anomalies along the coast of East Asia on 10‐ to 30‐day timescale, that is, ISMO1 and ISMO2. They both demonstrate obvious quasi‐biweekly oscillations with an equivalent barotropic structure in troposphere, and ISMO1 represents the southward propagating wave train with large variances in upper level, which is initiated from the West Europe and primarily forced by the soil moisture anomalies over mid‐high latitudes of Eurasian continent, whereas ISMO2 propagates northward in mid‐lower troposphere from the tropical western North Pacific to East Asia that is closely related to BSISO2. The two ISMOs are capable of explaining a large fraction of the total intraseasonal variances of EASM, wherein, ISMO1 is responsible for a meridional dipole pattern of precipitation anomalies over eastern China, while ISMO2 has major influence in southern China. Generally, ISMO‐caused changes of extreme precipitation probability are in good accordance with the spatial pattern of its related 10‐ to 30‐day intraseasonal precipitation anomalies. Since ISMO1 and ISMO2 can clearly separate the tropical and extratropical‐origin meridional oscillations and further have robust influences on precipitation over East Asia, they can be used as the new monitoring and predicting factors to the intraseasonal variations of EASM and their associated extreme precipitation. Key Points: Two intraseasonal meridional oscillations (ISMOs) over East Asia are identified with equivalent barotropic structure and biweekly periodISMOs can be forced by the tropical convection and the mid‐high latitude land surface and propagate northward and southward, respectivelyISMOs represent a large fraction of intraseasonal climate variations over East Asia and have significant impact on extreme precipitation [ABSTRACT FROM AUTHOR]

The model uncertainty, one of the major sources of projection uncertainty, is still a challenge in the climate change projection. In this study, the model uncertainty in simulating the East Asian summer monsoon rainfall and its physical link to the upper‐level jet streams and the western North Pacific subtropical high (WNPSH) are investigated from the Coupled Model Inter‐comparison Project Phase 6 (CMIP6) models. The results show that extracted by the inter‐model Empirical Orthogonal Function method, the leading inter‐model mode of the rainfall is characterized as a meridional pattern. The positive mode (a continent‐wet‐ocean‐dry pattern) is closely associated with a northward shift of the oceanic branch of the East Asian subtropical jet and a northward movement of the WNPSH, while the negative mode (a continent‐dry‐ocean‐wet pattern) is highly correlated with an enhanced East Asian polar‐front jet combined with a weakened land branch of the East Asian subtropical jet as well as a weakened and eastward recess of the WNPSH. This systematic link among the atmospheric circulations and the leading inter‐model mode is maintained by the negative phase of the Victoria Mode in the North Pacific and warming over the Atlantic Ocean in the positive mode, and the cooling over the Indian Ocean, Atlantic Ocean and the warming over the central Pacific in the negative mode. Our findings suggest that the physical linkage between the atmospheric circulations and monsoon rainfall is useful to understand the model uncertainty, which would be helpful in providing potential indicators of the East Asia summer monsoon change. Plain Language Summary: Monsoon rainfall has profound economic and social impacts, however large uncertainties lie in the climate model simulations. In this study, the inter‐model spread is used to extract the model uncertainty for the East Asian summer monsoon rainfall. The leading inter‐model mode is a meridional dipole pattern, which is closely associated with the concurrent variations of jet streams and the intensity and meridional movement of the western North Pacific subtropical high (WNPSH), but with the asymmetric response. The associated jet stream and the WNPSH variations are sustained by the oceanic conditions over the Atlantic Ocean, Pacific Ocean, and Indian Ocean, and therefore results in the inter‐model spread of the monsoon rainfall. Our findings suggest a useful metric to understand the traces of model uncertainties, focused on the physical linkage between the atmospheric circulations and the monsoon rainfall. Key Points: The leading inter‐model spread in East Asian summer monsoon rainfall is a meridional pattern from the Coupled Model Inter‐comparison Project Phase 6 modelsThe associated jet streams and western North Pacific subtropical high (WNPSH) variations exhibit asymmetric responses to this inter‐model spreadThe uncertainties in the north Pacific, Atlantic, and Indian Ocean have physically linked the jet stream and WNPSH variations to this inter‐model spread [ABSTRACT FROM AUTHOR]

Using a series of data from the National Oceanic and Atmospheric Administration (NOAA) and singular value decomposition (SVD) method, the dominant coupled mode between sea surface temperature (SST) anomaly in Maritime Continent (MC) and circulation anomaly in East Asia in summertime and its underlying mechanism are revealed. Results show that the first SVD mode is characterized by the in‐phase variations of SST anomaly in the entire MC and sea level pressure (SLP) anomaly in East Asia, and their co‐variation is measured by an SVD joint index, Isvd1 ${I}_{\mathrm{s}\mathrm{v}\mathrm{d}1}$. Based on composite difference fields, the ocean mixed layer heat budget reveals that the maintenance of the MC regional SST anomaly is jointly determined by ocean dynamics and heat flux. The anomalous SST warming near Java Island is dominated by the meridional advection of ocean current, while the SST warming in the Bay of Bengal, the South China Sea and the Northwest Pacific are mainly contributed by the increased downward latent heat flux and shortwave radiation flux. The SLP anomaly pattern in East Asia coupled with SST anomaly in the MC region is represented by the anomalous anticyclone in the Northwest Pacific, which can be maintained by the Isvd1 ${I}_{\mathrm{s}\mathrm{v}\mathrm{d}1}$‐related atmospheric vertical cell. The Isvd1 ${I}_{\mathrm{s}\mathrm{v}\mathrm{d}1}$‐related circulation anomalies tend to favor the summer precipitation in the middle and lower reaches of the Yangtze River and the south of Yunnan‐Guizhou Plateau, but lead to negative precipitation anomaly in central and Northeast China. Key Points: Summer sea surface temperature (SST) anomaly in the Maritime Continent (MC) varies in‐phase with sea level pressure anomaly in East Asia (EA)The MC SST‐EA circulation coupling mode is related to El Niño‐Southern Oscillation and maintained by the local ocean dynamical and thermodynamical processesThe anomalous circulation related to the coupling mode has important impact on summer precipitation in China [ABSTRACT FROM AUTHOR]

This study investigates the historical simulation of the Bay of Bengal–East Asia–Pacific (BEAP) teleconnection and its relationship with the El Niño–Southern Oscillation (ENSO) using 16 models from the Coupled Model Intercomparison Project phase 6 (CMIP6). The CMIP6 models can reasonably well reproduce the BEAP‐related diabatic heating variables and the ENSO sea surface temperature anomaly (SSTA). The CMIP6 models also show good performance in simulating the BEAP pattern at subseasonal and interannual time scales. Further investigation reveals that the BEAP–ENSO relationship changes from statistically insignificant to significant on an interdecadal timescale. Significant BEAP–ENSO correlation is associated with more positive SSTA over the tropical Indian Ocean (TIO) than in the period of insignificant BEAP–ENSO correlation. The positive SSTA difference acts as a heat source that intensifies the in situ atmospheric convection to generate considerable diabatic heating around the BEAP source region. The covariation of the Indo‐Pacific SSTA exhibits a tripole pattern, namely positive SSTA over the TIO, negative SSTA over the tropical central‐western Pacific, and positive SSTA over the tropical eastern Pacific. The SSTA tripole pattern is ascribed to the Indo‐Pacific capacitor effect and zonal advective feedback. The surface wind stress is weaker during the period of significant BEAP–ENSO correlation than during the non‐significant BEAP–ENSO period. The surface wind stress is also identified as a crucial factor in the projected changes in the BEAP teleconnection. The results indicate that the enhanced zonal wind stress results in more positive BEAP cases in the 21st‐century projection. Key Points: The Bay of Bengal–East Asia–Pacific (BEAP)–El Niño‐Southern Oscillation (ENSO) relationship changes from statistically insignificant to significant on an interdecadal timescaleSurface wind stress is a key factor for simulation of the BEAP teleconnection and the BEAP–ENSO relationshipEnhanced zonal wind stress results in more positive BEAP cases in 21st‐century projections [ABSTRACT FROM AUTHOR]

Previous studies have shown that increasing moisture convergence by transient eddies will cause winter precipitation increase in the future over the coastal lands in Eastern North America (ENA) and East Asia (EA). Using moisture budget and composite analyses, we investigate the physical processes responsible for the change of eddy moisture convergence and compare them between the two regions. We find that in addition to the "wet get wetter and dry get drier" ("WWDD") thermodynamic effect, changes in eddy moisture advection cause enhanced eddy moisture convergence north of 30°N and divergence to the south, with magnitudes comparable to the "WWDD" effect in these regions. The north‐south dipole pattern is reflected in the precipitation change of drying over the southern coastal lands in the future climate. It is caused by enhanced downgradient eddy moisture transport in the north and upgradient eddy moisture transport in the south, which is explained by the locations of the maximum magnitude of eddy relative humidity in conjunction with increase of mean saturation specific humidity. The eddy dynamic intensities associated with extreme precipitation events are found to increase in the future, contributing to the increase of eddy moisture convergence, but it plays a secondary role. The strong similarities of the underlying processes of eddy moisture change between ENA and EA suggest robust response of the spatially varying role of eddies in impacting future change of regional precipitation in ENA and EA. Key Points: There is enhanced eddy moisture convergence in the north and divergence in the south in both Eastern North America and East AsiaLocal thermodynamics associated with climatological wind convergence and increased moisture induces eddy convergence in the northSpatial thermodynamics generates eddy convergence in the north and divergence in the south due to maximum moisture fluctuation in the south [ABSTRACT FROM AUTHOR]

Inconsistencies in the Eocene climates of East Asia have been revealed in both geological studies and simulations. Several earlier reconstructions showed an arid zonal band in mid‐latitude China, but others showed a humid climate in the same region. Moreover, previous Eocene modeling studies have demonstrated that climate models can simulate both scenarios in China. Therefore, it is essential to investigate the cause of this model spread. We conducted a series of experiments using Norwegian Earth System Model 1‐F and examined the impact of mountains in Southern China on the simulated Eocene climate. These mountains, including the Gangdese and Southeast Mountains, are located along the main path of water vapor transport to East Asia. Our results reveal that the Southeast Mountains play the dominant role in controlling the simulated precipitation in Eastern China during the Eocene. When the heights of the Southeast Mountains exceed ∼2,000 m, an arid zonal band appears in mid‐latitude China, whereas humid climates appear in Eastern China when the elevation of the Southeast Mountains is relatively low. Key Points: Southeast Mountains control simulated Eocene precipitation in Eastern ChinaWhen the Southeast Mountains are high, an arid zonal band appears in mid‐latitude ChinaThe early Eocene climate in East Asia is not monsoonal climate [ABSTRACT FROM AUTHOR]

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

Understanding the climate controls of precipitation δ18O in the Tibetan Plateau (TP) is crucial for paleoclimate reconstructions from a wealth of regional archives. We use the outputs of iCAM5 model to quantify the different moisture contribution to local precipitation δ18O and to understand the climate controls of precipitation δ18O in the TP based on water‐tagging. The model shows some deficiencies in simulating the spatial and temporal characteristics of precipitation δ18O and the local climatic controls across the TP. Among all the tagged source regions, South Asia and the Indian Ocean contribute the most to the precipitation δ18O in the monsoon‐controlled domain, followed by the East Asia source region. The westerlies are identified as major moisture sources to the precipitation δ18O in the westerlies‐controlled domain. South Asia and the Indian Ocean also contribute substantially for the westerlies‐controlled domain. On interannual time scales, summer precipitation δ18O in the monsoon‐controlled domain is dominated by rainout processes occurring along the moisture transport pathway, indicating that precipitation δ18O variations here potentially record changes in the regional upstream convection. The δ18O signal can be altered by changes in the moisture source location, which implies that enhanced moisture delivery from remote source regions leads to more negative precipitation δ18O due to an increase in the rainout effect during transport. Our results have implications for the interpretation of past variations of archives with precipitation stable isotopes, such as ice cores, tree rings, lake sediments, and speleothems in the TP and surrounding regions. Plain Language Summary: Precipitation δ18O signal stored in climate proxy records from the Tibetan Plateau has long been used for paleoclimate reconstructions. However, the controls on precipitation δ18O over the TP remain debated. Studies of modern‐day climate controls on precipitation δ18O is crucial for interpreting past climate variations. We use the iCAM5 global atmospheric general circulation model fitted with water‐tagging capability to quantitatively decipher different climatic controls on precipitation δ18O across the TP. The model shows some deficiencies in simulating the spatial and temporal characteristics of precipitation δ18O and the local climatic controls across the TP. Among all the tagged source regions, South Asia and the Indian Ocean are identified as the most dominant moisture sources for the precipitation δ18O in the monsoon‐controlled domain, followed by the East Asia source region. For the westerlies‐controlled domain, the highest fractional contribution is from the westerlies. Changes in the rainout of water vapor during transport are the main driver of the interannual variability of precipitation δ18O in the monsoon‐controlled southern TP domain. The δ18O signal can be altered by changes in relative moisture contributions from different source regions. The amount effect contributes little to the precipitation δ18O variability in the southern TP. Key Points: Precipitation δ18O over the Tibetan Plateau (TP) is simulated with an AGCM implemented with water‐tagging capabilitySouth Asia and the Indian Ocean (the westerlies) contribute the most to precipitation δ18O in the southern (northern) TPVariability of precipitation δ18O in the monsoon‐controlled domain is dominated by rainout processes and moisture location changes [ABSTRACT FROM AUTHOR]

Pacific Decadal Variability (PDV) has enormous influences on North American and Eurasian climate and Pacific ecosystems. Its change under anthropogenic warming is of prodigious societal concern and scientific dispute. We show evidence that the observed PDV has amplified in the northeast Pacific horseshoe‐like region while weakened over the South Pacific and Kuroshio‐Oyashio Extension (KOE) region since the beginning of the 21st century. Congruently, under the influence of PDV, precipitation anomalies have significantly amplified globally and reversed the sign over Africa and East Asia. Analysis of the Coupled Model Intercomparison Project Phase 6 (CMIP6) historical simulations and future projections suggests that greenhouse forcing weakens the PDV in the South and northwestern Pacific and shortens its periodicity. However, the observed PDV's enhancement over the North Pacific eastern boundary is likely due to internal variability. Our findings on the PDV's response to anthropogenic forcing and internal variability shed light on the PDV's future change and decadal prediction. Plain Language Summary: Pacific Decadal Variability (PDV) is one of the primary modes of internal variability. There is an unprecedented change of the PDV after 1999, which reveals a sudden change in the spatial pattern, intensity, and climate impacts of the PDV. The amplitude of PDV has decreased over the South Pacific and Kuroshio‐Oyashio region but strengthened along the west coast of North America and equatorial central Pacific. This current PDV's cycle has amplified the land precipitation anomalies worldwide and reversed the precipitation anomalies over Africa, East Asia, and sub‐Arctic regions. We used the Coupled Model Intercomparison Project Phase 6 multi‐model results to illuminate that the recent unprecedented change of the PDV may be influenced by the combination of greenhouse warming and internal variability. Our findings reflect an advance in understanding the long‐term changes of the PDV and its remarkable impact on global land precipitation. Key Points: Observed Pacific Decadal Variability (PDV) has weakened over the South Pacific and Kuroshio‐Oyashio Extension while amplified over the northeast Pacific horseshoe‐like region since 1999Greenhouse gases forcing has a potential impact on weakening the PDV, which is also suggested by future warming scenarioThe increased PDV over the eastern boundary North Pacific and central Pacific may be associated with internal variability [ABSTRACT FROM AUTHOR]

It is well known that the El Niño‐Southern Oscillation (ENSO) has a profound impact on climate over southern China (SC). This study indicates that independent from the ENSO variability, a meridional tripolar sea surface temperature (SST) pattern over tropical‐North Pacific in February has a close relationship with interannual variations in the frequency of spring extreme consecutive dry days (extreme‐CDDs) over SC. Further analyses suggest that the tripolar SST pattern has a good persistence from February to the following spring and could influence the variations of SC extreme‐CDDs through two ways. On one hand, the extratropical SST anomalies of the tripolar pattern can cause the meridional shift of the North Pacific subarctic oceanic front, resulting in a meridional dipole atmospheric pattern over the region from the North Pacific to East Asia through eddy‐mean flow interaction. The meridional atmospheric pattern can influence the East Asian upper‐level jet and western Pacific subtropical high (WPSH), leading to anomalous vertical motion and moisture transport over SC. On the other hand, the SST anomalies of the tripolar pattern over the tropical western Pacific can excite an overturning circulation and influence the WPSH through the Matsuno‐Gill response, also contributing to anomalous vertical motion and moisture transport over SC. These physical processes are further confirmed by numerical simulations. Therefore, through the aforementioned two physical ways, the February tripolar SST pattern can influence the moisture and dynamical conditions associated with the occurrence of extreme‐CDDs, consequently providing a factor and predictor for the variations of SC spring extreme‐CDDs. Key Points: The interannual variations of spring southern China (SC) extreme consecutive dry days (extreme‐CDDs) are related to a tripolar sea surface temperature (SST) pattern over tropical‐North Pacific in FebruaryThe tripolar SST pattern affects SC extreme‐CDDs through mid‐latitude eddy‐mean flow interaction and tropical overturning circulationThe February tripolar SST pattern provides a prediction source for the interannual variations of SC spring extreme‐CDDs [ABSTRACT FROM AUTHOR]

The Pan‐Third Pole contains the largest number of glaciers outside the polar region that plays a crucial role in atmospheric circulation and the hydrological cycle. However, this pristine region has undergone rapid change through complex interactions including the black carbon (BC) enhanced warming effect and glacier melting. Study shows, Weather Research and Forecasting coupled with Chemistry (WRF‐Chem) simulation is able to capture distinctive seasonal variability of BC. The result from our sensitivity experiments revealed that South Asia (SA; 60.7%) and East Asia (EA; 32.9%) contributed more toward the Tibetan Plateau (TP). Our analysis on aerosol‐boundary feedback interaction revealed BC expand planetary boundary layer height by 5.0% and 4.8% over SA and EA, respectively, which facilitates BC dispersion and transportation. Whereas, we also found that under the influence of different wind regimes the significant BC transport flux aloft over the TP and the upper troposphere and lower stratosphere. Additionally, mountain‐valley channel and synoptic and local meteorological processes also facilitated BC transport to the TP. This study also evaluated the effect of BC on direct radiative forcing and calculated subsequent temperature changes. A strong dimming effect of BC corroborated with the following negative surface temperature changes. However, enhanced BC concentration during winter and spring caused the increase in temperature over the TP. Here, the WRF‐Chem model, synergy on aerosol‐boundary feedback, BC transport flux, and source‐receptor methods confirmed the significant BC contribution and transportation, and notable BC‐induced warming over TP. Such trans‐Himalayan BC transport and associated warming could grim glacier melt and water availability in the region. Key Points: Trans‐Himalaya long‐range transport is evident with significant black carbon (BC) transport flux aloft above Himalayas and Tibetan Plateau and free troposphere from South Asia (SA) and East Asia (EA) regionSynergy on aerosol‐boundary feedback interaction manifested that BC expand planetary boundary layer height by 5.01% and 4.80% over SA and EA, respectivelyElevated BC caused notable warming over Tibetan Plateau that could pose a threat in the cryosphere over that region [ABSTRACT FROM AUTHOR]

To better understand the characteristics of simulated raindrop size distributions (DSDs) and ice microphysical processes for convective systems in the East Asia monsoon region, a typical Meiyu event is simulated with the Weather Research and Forecasting (WRF) model using three two‐moment bulk microphysics schemes in this study. The simulated microphysical characteristics are then evaluated using polarimetric radar observations and retrievals. Although the observed linear storm structures are well simulated in terms of their location, there are significant deviations regarding simulated polarimetric radar variables and DSD parameters when compared to the observations. Compared to radar retrievals, all the simulated low‐level raindrops are found to have lower number concentration and larger mean sizes. To investigate the sources of the simulated DSD biases, vertical distributions of radar reflectivity and specific ice hydrometers (snow, graupel), as well as profiles of liquid/ice water contents from radar retrievals and simulations are further compared. In addition, variations about the occurrence frequency and transfer rate for four categories of ice processes (deposition, aggregation, riming, and melting) among the three schemes are analyzed. Results indicate that the overprediction of snow and graupel from riming processes is likely to be responsible for the production of extremely large raindrops at low levels. Key Points: Simulated microphysical structures for a Meiyu convective system were evaluated using polarimetric radar observations for the first timeRemarkable raindrop size distribution biases exist in the microphysics schemes when simulating this Meiyu caseThe extremely large raindrops in simulations are attributed to the overprediction of specific ice particles at higher levels [ABSTRACT FROM AUTHOR]

As a potential approach to counteract global warming, geoengineering has attracted much attention in recent years. We investigate the impacts of stratospheric aerosol injection (SAI) geoengineering on summer (June‐August, JJA) temperature and precipitation over East Asia as well as the East Asian summer monsoon (EASM) by using model outputs archived in the G4 stratospheric aerosol injection experiments of the Geoengineering Model Intercomparison Project (GeoMIP). In the G4 experiment, injected sulfate aerosols cause decreases in top‐of‐atmosphere radiative forcing, surface air temperature, and precipitation, and changes in the EASM and drought/flood pattern in summer over East Asia. The SAI‐induced temperature changes show consistent cooling with strong magnitudes over the East Asian continent, while the precipitation and EASM changes vary among regions and models. SAI leads to anomalous anticyclones in the lower troposphere, mainly due to the strong cooling in the middle‐to‐upper troposphere. The thermodynamic and dynamic mechanisms of SAI‐induced summer precipitation change over East Asia are analyzed through the moisture budget equation. The results show that the spatial pattern of precipitation change is dominated by a dynamic divergent component under SAI forcing, indicating the leading role of atmospheric circulation change. This change is closely associated with anomalous cyclones and anticyclones in the lower troposphere. Key Points: We investigate the climatic response of the East Asian summer climate to stratospheric aerosol injection geoengineering and the associated mechanismsContinuous stratospheric sulfate aerosol injection induces cooling over East Asia, while its impacts on precipitation and the East Asian summer monsoon vary among regions and modelsThe spatial pattern of the East Asian summer precipitation change arising from stratospheric aerosol injection geoengineering mainly results from the dynamic divergence component, which corresponds to the wind convergence and divergence in the lower troposphere [ABSTRACT FROM AUTHOR]

Recent changes in the Earth's climate have led to renewed interest in extreme cold wave (ECW) events. This study identifies the ECW patterns over the Chinese mainland, their corresponding large‐scale meteorological patterns (LMPs) and their favorable planetary wave patterns over 1961–2015. A self‐organizing map classifies ECWs into northeast, nationwide, northwest–south and Qinghai–Tibetan Plateau clusters. The cold anomalies are primarily contributed by the anomalous wind advecting climatological mean temperature for the leading three clusters, but diabaitic heating for the Qinghai–Tibetan Plateau cluster. The associated LMPs are primarily characterized by a dipole with a positive height anomaly over Siberia and a negative height anomaly extending from Japan to the Iranian Plateau, which displaces southwestward among the four ECW clusters. The LMPs induce anomalous northerly flows extending from the upper troposphere to the near‐surface, which deepen the negative height anomaly southwestward from the East Asian trough and accumulate cold air masses over the key regions within the dipole that are phase‐locked with the LMPs (i.e., baroclinic growth). Such baroclinic growth of the LMP is larger during periods of a planetary wave (wavenumbers 1–5) resembling the Northern Annular Mode (NAM). Meanwhile, the negative (positive) phase of the NAM provides more direct contribution to the LMP of the northeast and nationwide (Qinghai‐Tibetan Plateau) ECW clusters and thus are likely to favor the occurrence of ECWs. The negative phase of NAM‐like planetary waves exhibit a positive trend after the transition year of 1987, and could potentially increase the occurrence frequency of nationwide ECWs. Key Points: The gridded temperature data identify a new extreme cold wave (ECW) cluster over the Qinghai–Tibetan PlateauThe Northern Annular Mode–like daily planetary wave patterns contribute more to the anomalous circulation producing ECWs than othersThe increasing trend of ECW occurrence over the Chinese mainland is attributable to the Northern Annular Mode–like daily planetary wave [ABSTRACT FROM AUTHOR]

The East Asian coastal mountains have been in place during the Late Cretaceous times, thus substantially influencing the Asian climate. So far, their altitude is uncertain. Here we investigate the influence of such mountains on Asian climate using an atmosphere‐ocean general circulation model, Community Earth System Model version 1.2.2. Simulation results show that extensive deserts would develop over the eastern part of the East Asia if the altitude of the coastal mountains was greater than 2 km. This is due to the pumping effect of the coastal mountains which deprives the moisture from the East Asian interior during summer and autumn, leading to less precipitation and greater potential evapotranspiration. The existence of extensive desert areas would be more consistent with the presented Asian paleoenvironmental reconstructions. Therefore, our results independently indicate that the altitude of the coastal mountains had attained 2 km or more by the early Late Cretaceous. Key Points: The East Asian coastal mountains had risen to 2 km or higher during the early Late CretaceousThe East Asian coastal mountains had a drying effect on the Asian climate during the Late CretaceousThe East Asian coastal mountains decreased the Asian precipitation by means of their pumping effect [ABSTRACT FROM AUTHOR]

Countries in East Asia have set ambitious goals for the development of wind energy to meet the increasing energy demand and to mitigate anthropogenic climate change. However, few studies have investigated changes in wind energy over East Asia under future climatic conditions. In this study, we investigate future changes of 100‐m wind speed and wind energy potential over the CORDEX‐East Asia region under the Representative Concentration Pathway (RCP) 8.5 scenario, by using ensemble simulations from the regional climate model Consortium for small‐scale modeling in CLimate Mode (CCLM). A multivariate bias adjustment method based on the N‐dimensional probability density function transform is used to correct raw simulated horizontal wind components. The comparison between future climate (2021–2050 and 2070–2099) and the present climate (1971–2000) shows decreases in wind speed, wind power density, and wind energy output over most of the CORDEX‐East Asia region, especially in the tropics. Projected increases are pronounced over the Himalayan regions, the Indo‐China Peninsula, the South China Sea, and the western Pacific Ocean in summer and over northeastern China, parts of Western China and the Indo‐China Peninsula in winter. Interannual and intra‐annual variability of wind power density are projected to intensify significantly for most of the CORDEX‐East Asia region. The occurrence of weak wind speeds (<3 m/s) is projected to increase, while strong wind speeds (>11 m/s) are projected to decrease over most of the ocean. Key Points: Future changes in 100‐m wind energy potentials over CORDEX‐East Asia are evaluated by using CCLM ensemble simulationsThe multivariate bias adjustment method is used to correct raw simulated wind components and is shown to be robust in reducing biasWind energy potentials are projected to decrease over most of the CORDEX‐East Asia region, especially for 2070–2099 [ABSTRACT FROM AUTHOR]

Black carbon (BC), brown carbon, and light‐absorbing iron oxides (FeOx) aerosols affect Earth's energy budget through their strong absorption of solar radiation. FeOx aerosols can also affect global biogeochemical cycles through their role as a nutrient for oceanic phytoplankton. However, observational data for these aerosols required for evaluating their effects using global models are scarce, especially for FeOx. Here, we summarize and compare the data sets of BC and FeOx from five ground‐based and three aircraft observation campaigns conducted in the East Asian and Arctic regions during the 2009–2018 period acquired using a modified single‐particle soot photometer. In these campaigns, >80% of FeOx‐containing aerosols in the 170–270 nm FeOx core size range had microphysical features indicating an anthropogenic origin. The particle size distribution for each of the BC and FeOx was similar in all of the data sets except for those dominated by fresh urban pollution or pristine Arctic air. The campaign‐averaged mass concentrations of FeOx and BC were ~60–360 ng/m3 and ~240–1,300 ng/m3, respectively, in East Asia, and ~6 ng/m3 and ~20–30 ng/m3, respectively, in the Arctic. The campaign‐averaged FeOx/BC mass concentration ratio varied within a narrow range of 0.2–0.6 in both East Asian and Arctic regions. In every campaign, FeOx, BC, and carbon monoxide were tightly correlated with each other with similar slope to the urban campaigns (around Tokyo), implying the spatiotemporal variation of anthropogenic FeOx emission around northern middle‐to‐high latitudes is similar to those of anthropogenic BC and CO emissions. Key Points: Mass concentrations of anthropogenic iron oxide (FeOx) were at least 20% of those of black carbon (BC) in both East Asia and the ArcticFeOx, BC, and carbon monoxide were tightly correlated with each other in both East Asia and the ArcticParticle size distributions of both FeOx and BC were presented and compared in detail [ABSTRACT FROM AUTHOR]

The winter temperature in East Asia from 1958 to 2001 has shown an obvious warming trend superposed with a large amplitude of decadal oscillations. To separate the relative contributions of external forcing and internal variability to the decadal change in winter temperature, we propose a method which combines reanalysis data, global atmosphere‐ocean coupled model outputs, and regional climate model. The results show that the weakening of the East Asian winter monsoon accounts for warming trend in the south Mongolia, the southeastern coast of Asia, and the adjacent seas to a large extent. In contrast, radiative forcing causes the warming trend in middle and high latitudes. The increasing concentration of aerosols could have resulted in local cooling in some areas. The winter temperature shows a decadal oscillation of 0.6 °C at a time scale of 8–20 a, which is mainly due to the oscillation of the Siberian‐Mongolia High and volcanic activities. The amplitude of temperature oscillations caused by volcanic activities was one third of that induced by the Siberian‐Mongolia High. Key Points: The winter warming in East Asia during 1958–2001 was due to greenhouse gas emissions and the weakening of the East Asia winter monsoonRadiative‐forced warming had a uniform pattern, while the warming caused by weakening monsoon was located in the eastern coast of EurasiaVolcanic aerosols caused an interdecadal oscillation of 0.2 °C, which was one third of the strength caused by internal variability [ABSTRACT FROM AUTHOR]

This study revisits precipitation change in East Asia caused by the Madden‐Julian oscillation (MJO) and its interannual variation due to the quasi‐biennial oscillation (QBO). Specifically, boreal‐winter precipitation, derived from weather stations across China, Korea, and Japan, is examined for MJO phases 2–3 and 6–8. Consistent with previous findings, precipitation in southern China and southern Japan increases by up to 36% during MJO phases 2–3, when the MJO convection is located in the Indian Ocean. In contrast, during MJO phases 6–8, precipitation decreases by 13%. More importantly, these MJO‐related precipitation anomalies become larger and more organized when the QBO is in its easterly phase. The difference in precipitation anomalies between the QBO easterly and westerly phases is approximately 40% for MJO phases 2–3 and 70% for MJO phases 6–8 from southern China to Japan. This result reaffirms that the QBO can affect surface weather in the northern extratropics through MJO teleconnection. Plain Language Summary: Deep convections in the tropics influence distant regions via propagation of energy in the form of waves. With its change dominant on the intraseasonal timescale, the Madden‐Julian oscillation (MJO) is known to change daily winter precipitation in East Asia. At the same time, far above in the tropical stratosphere, there is a year‐to‐year variation in zonal wind called the quasi‐biennial oscillation (QBO). It is widely believed that the MJO is stronger and more persistent when the QBO blows from east to west (easterly) than when it blows from west to east. Based on this belief, how MJO‐induced precipitation in East Asia is affected by the QBO is investigated. As expected, the degree of change in precipitation is larger with a stronger MJO amplitude during easterly QBO winters. During easterly QBO winters, MJO‐induced vertical motion near coastlines of East Asia is amplified by stronger upper‐level circulations. Furthermore, moisture transport from the subtropics is also enhanced with the stronger low‐level circulation in easterly QBO winters. In the sense that the QBO has a longer timescale as well as a longer memory than the MJO, we expect to utilize the QBO to predict MJO‐related surface weather changes in the extratropics better and earlier. Key Points: The MJO‐induced precipitation anomaly in East Asia is significantly influenced by QBO phaseThe MJO teleconnection in East Asia is strengthened during easterly QBO winters, when the MJO amplitude is enhancedThe moisture supply to East Asia by MJO‐induced circulation is enhanced during easterly QBO winters [ABSTRACT FROM AUTHOR]

The increased mean temperature and temperature variability under global warming can have many adverse impacts on human and natural systems. However, how soil moisture‐atmosphere interaction can affect future climate change over East Asia remains largely unclear. We use long‐term regional climate simulations with the Community Climate System Model‐Weather Research and Forecasting (CCSM‐WRF) model system to investigate the role of soil moisture feedbacks in future summer surface air temperature change over East Asia. Results show that summer surface air temperature and precipitation are projected to increase over most of East Asia by the end of 21st century under the Representative Concentration Pathway 8.5 (RCP8.5) scenario. Soil moisture feedbacks lead to an increased summer mean temperature of 0.15°C averaged over East Asia, with key regions appearing over the northern part of Tibetan Plateau, Sichuan Basin, and the middle and lower reaches of the Yangtze River Basin during 2071‐2100 under the RCP8.5 scenario. And regionally averaged interannual temperature variability induced by soil moisture feedbacks is substantially enhanced as a whole. Regarding the spatial distribution, soil moisture feedbacks on interannual temperature variability are projected to strengthen notably over the northern part of Tibetan Plateau, the Hexi Corridor, and Sichuan Basin and weaken over the south Tibetan Plateau, southeast China, and the areas surrounding the Lake Baikal. The stronger responses of surface heat and the atmospheric boundary layer to dry anomalies than wet anomalies lead to an obvious dry‐wet asymmetry of soil moisture feedbacks on summer surface air temperature over the key areas of East Asia. Key Points: Soil moisture feedbacks enhance future regionally averaged summer temperature change in terms of mean state and interannual variabilityThe spatial distribution of soil moisture feedbacks on interannual temperature variability is projected to substantially changeFuture temperature change responds much more strongly to dry anomalies than wet anomalies of soil moisture over key areas of East Asia [ABSTRACT FROM AUTHOR]

The long‐term trend in dust loading over East Asia remains under debate and is dependent on the study period chosen. In this study, the long‐term trends in springtime dust over East Asia and the North Pacific Ocean (NPO) during 1980–2017 were examined based on the Modern‐Era Retrospective Analysis for Research and Applications version 2 reanalysis. Results showed that there was a spatial gradient in dust aerosol loadings, with decreases from western China eastward toward the NPO. This pattern was corroborated by Cloud‐Aerosol Lidar with Orthogonal Polarization observations. Furthermore, the empirical orthogonal function method was used to reveal the leading modes of springtime dust aerosol optical depth (AOD) over East Asia and the NPO. An abrupt shift occurred in the dust AOD trend in 2010 for the empirical orthogonal function 1 mode. The dust AOD increased at a rate of approximately 2 × 10‐4/year during 1999–2009 and then decreased more sharply (around 5 × 10‐4/year) afterward. This trend reversal of dust AOD was closely associated with a decrease in 10‐m wind velocity, which induces reduced dust emission. Compared with 10‐m wind, the soil moisture is less correlated with the trend reversal in dust AOD. Additionally, the trends of dry (wet) deposition were closely associated with the trends of the dust AOD, especially for the period 2010–2016. Overall, our findings add new insights to the long‐term nonlinear variability of dust. Plain Language Summary: Dust aerosols originating from East Asia (EA) play an important role in the Earth's climate system, due to their strong radiative effects. The long‐term trend in dust loading in this region and surrounding areas remains unclear and is dependent on the study period chosen. Here, we investigated the long‐term trends in springtime dust aerosols over EA and the North Pacific Ocean (NPO) for the period 1980 to 2017, using the Cloud‐Aerosol Lidar with Orthogonal Polarization observations, along with the Modern‐Era Retrospective Analysis for Research and Applications version 2 reanalysis. Time series analyses from Rodionov sequential algorithm indicated that the springtime dust aerosol optical depth (AOD) over EA&NPO experienced an abrupt shift in 2010. The dust AOD increased (2 × 10‐4/year) during 1999–2009, followed by a decreasing trend (5 × 10‐4/year) afterward. Besides, the roles of atmospheric circulation, deposition, and soil moisture in the shift in springtime dust aerosol trends were further analyzed. The decrease in 10‐m wind velocity and reduced dry deposition partly account for this decreasing trend in dust AOD for the period 2010–2016. Our findings provides an insightful look into the drivers for the trend reversals observed in EA&NPO. Key Points: The dust AOD in East Asia and the North Pacific Ocean increased during 1999–2009 and dropped sharply afterwardThe trend reversal of dust AOD was partly attributed to the decrease in 10‐m wind velocity that leads to reduced dust emissionThe trends of dry‐and‐wet deposition were tightly associated with the trends of the dust AOD, especially for the period 2010–2016 [ABSTRACT FROM AUTHOR]

Using the data from ERA‐interim, the Hadley Centre Global Sea Surface Temperature data set, and the Climate Prediction Center Merged Analysis of Precipitation, after removing the simultaneous El Niño and Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) signals, we have investigated variations of anomalous convergence around Kalimantan Island in lower troposphere in associations with the East Asian summer and Australian winter monsoons. Results indicate that when negative sea surface temperature anomalies appear in the western Pacific on both sides of the equator, the atmospheric cooling over the northwestern Pacific and from the South Pacific Convergence Zone (SPCZ) to Australia is favorable for the maintenance of anticyclonic anomalies over the areas from the western Pacific to the South China Sea and from the south of the equator to the northeast of Australia. These anomalous anticyclonic circulations can induce equatorial easterly anomalies, which subsequently facilitate the maintenance of anomalous convergence around Kalimantan Island. In turn, the anomalous convergence in Kalimantan Island is favorable for the maintenance of anomalous anticyclonic over the northwestern Pacific and SPCZ and thereby intensifies both the western Pacific subtropical high and the Australian High, inducing concurrent intensifications of the East Asian summer monsoon and Australian winter monsoon. Related to the anomalous convergence over Kalimantan Island, precipitation and temperature decrease from the western Pacific to SPCZ but increase from the Indian Ocean to western Maritime Continent and Australia, while temperature is lower than normal in Kalimantan. The above results have remarkable implications for in‐depth understanding of the mechanism behind anomalies of the East Asian summer monsoon and Australian winter monsoon. Key Points: The anomalous convergence in Kalimantan Island is related to the forcing of SST anomalies in the Pacific and Indian OceanThe convergence anomaly in Kalimantan Island is highly correlated with anomalous activities of the Australian High and the WPSHCirculation anomalies related to the anomalous convergence in Kalimantan Island would affect climate variations in East Asia and Australia [ABSTRACT FROM AUTHOR]

Heat waves are the leading weather‐related cause of death in the United States, with the most recent examples occurring in the summers of 2011 and 2012 over the Great Plains. These events are unusual and largely unpredictable beyond the synoptic timescale. Their number and severity have increased and are projected to continue to increase, prompting the need to identify the physical processes that modulate heat waves and, consequently, can lead to improved prediction and future projection. Our results based on observations and model simulations suggest that convective latent heat release from the East Asian Monsoon enhances the likelihood of droughts and heat waves over the United States through an equivalent barotropic wave train along the subtropical jet stream, promoting an anticyclonic circulation pattern over the Great Plains. This anticyclone serves as a blocking pattern for transient synoptic‐scale systems and is supportive of persistent drought and clear sky conditions, promoting high temperatures and heat waves. Key Points: The influence of the East Asian Monsoon (EAM) on the summer climate of the Great Plains of the United States is investigatedThe EAM forces an upper‐level ridge over the Great Plains of the United States, increasing temperature and drought over that region in boreal summerThe amplitude and frequency of occurrence of heat waves increases as a result of the reduced precipitation and stagnant circulation [ABSTRACT FROM AUTHOR]

A new teleconnection pattern (the BEAP) across the Bay of Bengal‐East Asia‐Pacific region in boreal summer is revealed in this study using mainly ERA‐Interim reanalysis data from the European Centre for Medium‐Range Weather Forecasts. The BEAP index (BEAPI) is defined as the signed sum of standardized apparent moisture sinks at five centers along the pathway. Correlation analysis of the apparent heat sources and apparent moisture sinks has verified the existence of the BEAP teleconnection. Variations in BEAP can affect precipitation anomalies resulting from the anomalous moisture transport and the antiphase surface temperature variation. Wave flux analysis has verified the Rossby wave propagation route that originates around the central Bay of Bengal and extends across North China to the West Pacific. La Niña‐type sea surface temperature anomalies (SSTAs) appearing simultaneously in the same season can excite a positive BEAP pattern by enhancing convection over the Bay of Bengal, while El Niño‐type SSTAs have the opposite effect. Significant correlation between the BEAPI and the SSTAs can last from early summer to early winter. Numerical experiments confirm the BEAP teleconnection pattern and the associated physical processes. Key Points: The BEAP teleconnection is excited by the latent‐heat release over Bay of BengalENSO, especially the SST over tropical western Pacific, plays a key role in affecting the interannual variability of BEAP teleconnectionThe BEAP teleconnection is closely related to the precipitation or surface temperature in East Asia [ABSTRACT FROM AUTHOR]

Abstract: The tropical cyclone (TC) in East Asia varies strongly each year, indicating the different spectral characteristics of the TC cloud systems (TCCSs) with the distance from the center of TC. We report a new perspective of optical properties of TCCS by using the Moderate Resolution Imaging Spectroradiometer and Tropical Rainfall Measuring Mission data over the years from 2010 to 2014 for the 35 TCs in East Asia. We investigate the spatial distribution of the cloud‐top height, radar reflectivity, polarization corrected temperature in 85.5 GHz (PCT85.5), hydrometeor vertical profile, cloud water path, cloud optical thickness, and cloud particle effective radius of TCCS in the development, maturity, and decay stages of TC. The results indicate the significant differences of cloud characteristics in the maturity stage in comparison to other two stages, showing the higher radar reflectivity up to 30 dBZ and the PCT85.5 as low as 232.98 K in the TC eye wall. Meanwhile, the mean hydrometeor profile indicates more ice particles accumulating above the height of 10 km but less liquid droplets near 3 km. The peak of cloud water path and cloud optical thickness in the maturity stage can reach to 1,300 g/m2 and 75, respectively. The mean cloud particle effective radius and precipitation in the three stages could be influenced by aerosols. Based on these quantified results, several ideal fitting equations and the models are constructed to denote the properties of TCCS. Two cases are analyzed to examine the accuracy of the quantified mean state for different stages of TCCS and the relationship between aerosols and clouds. [ABSTRACT FROM AUTHOR]