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Extreme high temperatures occur frequently over the densely populated Yangtze River basin (YRB) in China during summer, significantly impacting the local economic development and ecological system. However, accurate prediction of extreme high-temperature days in this region remains a challenge. Unfortunately, the Climate Forecast System Version 2 (CFSv2) exhibits poor performance in this regard. Thus, based on the interannual increment approach, we develop a hybrid seasonal prediction model over the YRB (HMYRB) to improve the prediction of extreme high-temperature days in summer.The HMYRB relies on the following four predictors: the observed preceding April–May snowmelt in north western Europe; the snow depth in March over the central Siberian Plateau; the CFSv2-forecasted concurrent summer sea surface temperatures around the Maritime Continent; and the 200-hPa geopotential height over the Tibetan Plateau. The HMYRB indicates good capabilities in predicting the interannual variability and trend of extreme high-temperature days, with a markable correlation coefficient of 0.58 and a percentage of the same sign (PSS) of 76% during 1983–2015 in the one-year-out cross-validation. Additionally, the HMYRB maintains high PSS skill (86%) and robustness in the independent prediction period (2016–2022). Furthermore, the HMYRB shows a good performance for years with high occurrence of extreme high-temperature days, with a hit ratio of 40%. These predictors used in HMYRB are beneficial in terms of the prediction skill for the average daily maximum temperature in summer over the YRB, albeit with biases existing in the magnitude. Our study provides promising insights into the prediction of 2022-like hot extremes over the YRB in China. [ABSTRACT FROM AUTHOR]

We used observational data and a long‐term piControl simulation from the Community Earth System Model Version 2 to investigate the influence of the Pacific Decadal Oscillation (PDO) on the winter climate over the Tibetan Plateau. The results showed that changes in the phase of the PDO have a significant effect on winter temperatures and precipitation over the southern Tibetan Plateau. Changes in the sea surface temperature (SST) during the positive PDO can weaken the Walker circulation and increase the SST in the Indian Ocean. Our analyses of the moist static energy showed that warming of the tropical troposphere over the Indian Ocean caused by the increased SST has resulted in the horizontal advection of anomalous moist enthalpy by the climatological zonal winds, which was responsible for anomalous ascending motion over the Tibetan Plateau. The additional moisture budget suggests that enhanced vertical motion contributes to the increase in winter precipitation and related total cloud cover over the Tibetan Plateau, leading to the increase of snow depth. The increased total cloud cover and snow depth, in turn, reduces net surface shortwave radiation. The surface air temperature of the Tibetan Plateau is then decreased as a result of the reduction in the net surface shortwave radiation. The PDO therefore has an important modulating role in the interdecadal variability of the winter climate over the Tibetan Plateau. We therefore need to focus on changes in the PDO in research related to the decadal prediction of the climate over the Tibetan Plateau. Plain Language Summary: Under the background of global change, the climate of the Tibetan Plateau has undergone significant changes, and it has an important impact on the regional and global climate. Therefore, it is very important to find out the mechanisms of climate variabilities on the Tibetan Plateau. In this study, we aim to investigate the influences of the Pacific Decadal Oscillation (PDO) on the winter climate of the Tibetan Plateau and the related physical mechanisms by using observational data and a long‐term piControl simulation from the Community Earth System Model Version 2. Results suggest that the PDO has an important modulating role in the interdecadal variability of the winter climate over the Tibetan Plateau. The positive PDO phase can increase winter precipitation and decrease the surface air temperature of the Tibetan Plateau. The related mechanisms are also investigated in this study. Key Points: The positive Pacific Decadal Oscillation (PDO) can increase the precipitation and thereby decreasing the temperature in winter over the southern Tibetan PlateauThe horizontal advection of anomalous moist enthalpy is responsible for anomalous ascending motion and increased precipitationThe anomalous advection of zonal warm air is caused by warming of the tropical troposphere over the Indian Ocean due to the positive PDO [ABSTRACT FROM AUTHOR]

Deciphering the Meiyu behavior during the Last Interglacial (∼127 ka; LIG) may deepen our understanding of drought and flooding events over East Asia in a warmer‐than‐present world induced by Earth's orbit. Based on dynamical downscaling simulations, we suggested a 15‐ and 30‐day earlier onset and retreat of the Meiyu during the LIG relative to preindustrial, respectively, leading to a shortened Meiyu season. Meantime, extreme precipitation in the Meiyu season became stronger and occurred more frequently. Intensified monsoonal circulation, poleward‐located western North Pacific subtropical high, and poleward shift of East Asian westerly jet during the LIG provided favorable moisture conditions for earlier onset and retreat of the Meiyu. The variations of atmospheric circulations were further regulated by the joint effect of the three oceans and diabatic heating over Tibetan Plateau. Our results highlight an important role of Earth's orbit in the Meiyu and imply more flooding events in a warmer world. Plain Language Summary: The record‐breaking Meiyu in 2020 reemphasizes the importance of investigating the evolution of the rainy season in East Asia. This study reveals the response of the Meiyu to changes in the Earth's orbit during the Last Interglacial (LIG, 130–115 ka)—the warmest interglacial of the past 800 ka and a warmer world comparable to the low emission scenarios at the end of the 21st century. The Meiyu season occurred and ended earlier compared with the present day, and the duration was shortened. Additionally, more frequent and intense extreme precipitation events occurred in the Meiyu season during the LIG. The enhanced East Asian summer monsoonal flow, strengthened western North Pacific subtropical high, and poleward shift of the East Asian westerly jet in June provided favorable conditions for the earlier occurrence and termination of the Meiyu during the LIG. Moreover, changes in the sea surface temperature over the three oceans can jointly influence the Meiyu via triggering Kelvin waves, Rossby waves, and teleconnections by atmospheric circulations, with the contribution from the diabatic heating over the Tibetan Plateau. The results of this study help us better understand the evolution of the rainy season over East Asia in a warmer world. Key Points: Earlier onset and shortened duration of Meiyu season during the Last Interglacial (LIG)Stronger and more frequent extreme precipitation events occurred in Meiyu season during the LIGIntensified monsoonal circulation, poleward‐located subtropical high and westerly jets led to changes in Meiyu during the LIG [ABSTRACT FROM AUTHOR]

The South Asian high (SAH) experienced a decadal weakening in the late 1970s under global warming. Based on an evaluation of the historical runs from CMIP6 models, we quantitatively assessed the contributions of different external forcing using "good" models that reasonably simulated the decadal decline of the SAH. All‐forcing runs yielded the weakened SAH after the late 1970s, albeit the decadal decline was underestimated by most models. Compared to the insignificant contributions of greenhouse gas and natural forcing, anthropogenic aerosol played a dominant role in the decadal decline of the SAH. The increased aerosol likely drove a cooling surface over the Tibetan Plateau (TP) and East China via its effect on radiation. Consequently, the weakened heat source over the TP and associated thermodynamic effects over East China would have driven a cooling of eddy temperature and cyclonic anomalies in the upper troposphere, respectively, thereby causing the decline of the SAH. Plain Language Summary: Under global warming, the South Asian high (SAH) measured by eddy geopotential height experienced a decadal decline in the late 1970s. However, the mechanism responsible for the decadal decline of the SAH has not been investigated. In this study, the contributions of external forcing to the decadal decline of the SAH are accessed using "good" CMIP6 models that can reasonably simulate the decadal changes of SAH. Results indicate that anthropogenic aerosol plays an important role in weakening the SAH. The increased aerosol emission over the Tibetan Plateau (TP) and East China cools the ground through the radiation effect. The weakened heat effect of TP and East China can contribute to the weakening of SAH. By contrast, the contributions of greenhouse gas and natural forcing are almost completely insignificant due to their homogenized and only very slight effects on the upper‐tropospheric eddy temperature over the SAH region, respectively. Key Points: ALL forcing can yield a weakening of the South Asian high (SAH), and anthropogenic aerosol provided the dominant contributionAnthropogenic aerosol drove the decline of the SAH by weakening the effect of the heat source over the Tibetan PlateauThe contribution of greenhouse gas and natural external forcing to the decadal decline of the SAH is insignificant [ABSTRACT FROM AUTHOR]

Investigation of the variations of hydrological cycles during the Last Interglacial (130–115 ka; LIG) may deepen our understanding of climate change in a warmer‐than‐present world induced by Earth's orbit. Here we revealed an intensified atmospheric branch of the hydrological cycle over the Tibetan Plateau (TP) in summer during the LIG relative to the preindustrial period, using the mesoscale Weather Research and Forecasting model driven by the Community Earth System Model. Our results showed that precipitation over the TP increased by 5.65 × 107 kg s−1, with 63.2% of the increase contributed by advected moisture transports, and the remaining 36.8% caused by local moisture recycling processes. As for advected moisture transports, the inflow increased by 1.93 × 107 kg s−1 and the outflow decreased by 0.87 × 107 kg s−1, respectively. Variations of the moisture transport were more profound at the eastern and northern edges, which were linked with changes in Indian summer monsoon and westerly jets. Regarding local moisture recycling processes, evaporation enhanced by 2.85 × 107 kg s−1 over the TP, influenced by variations in surface air temperature, surface net radiation flux, surface relative humidity, and surface wind fields. Increased evaporation accompanied by enhanced moisture inflow resulted in an enriched precipitation recycling ratio of ∼1% over the TP during the LIG relative to the preindustrial in summer. Our results aid in understanding the atmospheric branch of the hydrological cycle over the TP in an orbit‐induced warmer world and shed light on the future evolution of the hydrological cycle over the TP at multi‐millennial and orbital timescale. Key Points: Dynamical downscaling simulations for the Last Interglacial from Weather Research and Forecasting driven by Community Earth System ModelIntensified atmospheric branch of the summer hydrological cycle over the Tibetan Plateau during the Last Interglacial (LIG)Intensified hydrological cycle was manifested in both external and internal cycles during the LIG [ABSTRACT FROM AUTHOR]

The changing characteristics of lake ice phenology over the Tibetan Plateau (TP) are investigated using historical satellite retrieved datasets during 2002–15 in this study. The results indicate that the freezing process mainly starts in December, and the ice melting process generally occurs in April for most lakes. However, the changes in lake ice phenology have varied depending on the location in recent years, with delayed break-up dates and prolonged ice durations in the southern TP, but no consistent changes have occurred in the lakes in the northern TP. Further analysis presents a close connection between the variation in the lake ice break-up date/ice duration over the southern TP and the winter North Atlantic Oscillation (NAO). The positive NAO generally excites an anomalous wave activity that propagates southward from the North Atlantic to North Africa and, in turn, strengthens the African–Asian jet stream at its entrance. Because of the blocking effect of the TP, the enhanced westerly jet can be divided into two branches and the south branch flow can deepen the India–Myanmar trough, which further strengthens the anomalous cyclonic circulation and water vapor transport. Therefore, the increased water vapor transport from the northern Indian Ocean to the southern region of the TP can increase the snowfall over this region. The increased snow cover over the lake acts as an insulating layer and lowers the lake surface temperature in the following spring by means of snow–ice feedback activity, resulting in a delayed ice break-up date and the increased ice duration of the lakes over the southern TP in recent years. [ABSTRACT FROM AUTHOR]

The near-surface freeze/thaw cycle in cold regions plays a major role in the surface energy budget, hydrological activity, and terrestrial ecosystems. In this study, the Community Land Model, Version 4 and a suite of high-resolution atmospheric data were used to investigate the changes in the near-surface soil freeze/thaw cycle in response to the warming on the Tibetan Plateau from 1981 to 2010. The in situ observations-based validation showed that, considering the cause of scale mismatch in the comparison, the simulated soil temperature, freeze start and end dates, and freeze duration at the near-surface were reasonable. In response to the warming of the Tibetan Plateau at a rate of approximately 0.44 °C decade, the freeze start-date became delayed at an area-mean rate of 1.7 days decade, while the freeze end-date became advanced at an area-mean rate of 4.7 days decade. The delaying of the freeze start-date, which was combined with the advancing of the freeze end-date, resulted in a statistically significant shortening trend with respect to the freeze duration, at an area-mean rate of 6.4 days decade. Such changes would strongly affect the surface energy flux, hydrological processes, and vegetation dynamics. We also found that the rate of freeze-duration shortening at the near-surface soil layer was approximately 3.0 days decade lower than that at a depth of 1 m. This implied that the changes in soil freeze/thaw cycles at the near surface cannot be assumed to reflect the situation in deeper soil layers. The significant correlations between freeze duration and air temperature indicated that the shortening of the near-surface freeze duration was caused by the rise in air temperature, which occurred especially in spring, followed by autumn. These results can be used to reveal the laws governing the response of the near-surface freeze/thaw cycle to climate change and indicate related changes in permafrost. [ABSTRACT FROM AUTHOR]

In this study, a Lagrangian particle dispersion model, Flexible Particle (FLEXPART), is employed to simulate the trajectories of global air parcels during 2000-09 with the purpose of revealing the moisture sources of the semiarid grasslands of China, especially on precipitation days. Based on land-cover and precipitation data, two areas of semiarid grasslands are identified: one in North China and one in the Tibetan Plateau. Using the FLEXPART simulation results, air parcels reaching these two target regions are traced back for 10 days to examine their temporal variations in position (longitude, latitude, and altitude) and specific humidity. The moisture sources of these semiarid grasslands are discussed for different precipitation categories. Moreover, the contributions of different moisture sources to the precipitation in the target regions are computed and compared. The results indicate that the moisture released in the target regions is substantially from the Eurasian continent, in both summer and winter. During May-September, the southern and eastern adjacent land areas seem to be the main moisture sources of rainfall in the grasslands of North China, while the Eurasian continent on the north and west tends to be the predominant contributor to the rainfall over the grasslands of the eastern Tibetan Plateau. During October-April, moistures released in both target regions principally originate from the Eurasian continent on the north and west. Overall, although the moisture uptake over oceanic sources is also considerable, most released moisture over the target regions is from the Eurasian continent throughout the year, while little of the contribution of oceanic sources is due to great loss of moisture en route. [ABSTRACT FROM AUTHOR]

We have identified the northern Tibetan Plateau as having experienced the most significant warming of any region in the entire plateau domain since 1961. Warming in the northern plateau violates the previously suggested elevation dependency of warming trends. Further analysis shows that the increase in surface air temperature in summer has played a primary role in the rapid increase of the annual mean air temperature in the northern Tibetan Plateau since the mid-1980s. In addition, the summer air temperature is correlated with ozone in the region, a result which is statistically significant. This correlation seems to have a relationship with solar radiation and ozone depletion ratios. Further discussion shows that the most significant warming in the northern plateau may be related to radiative and dynamical heating that are results of pronounced stratospheric ozone depletion. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Geographic variations in summer (July-August) precipitation data for the northern Qinghai-Xizang (Tibetan) Plateau, collected during the lOP (Intense Observation Period) of GAME-Tibet, were examined. Results indicated that, basically, the daily precipitation amount consistently varies temporally at all sites. An increase in precipitation amount is evident from north to south. The distribution of summer monsoon precipitation is affected by latitude, altitude, and other factors (i.e. atmosphere circulation, water vapor transportation). The latitude effect of precipitation in July and August was significant. August precipitation varied with both latitude and altitude. The site with higher elevation received more precipitation. Topoclimatic controls operating over precipitation on slopes include elevation. The distribution of the precipitation during July-August mainly showed the effects of latitude, but this was modified by the altitude effect. Redistribution processes caused by topography induce increased precipitation with altitude at some sites. Owing to the complexity of surface conditions on the Qinghai-Xizang (Tibetan) Plateau, precipitation is controlled by many factors simultaneously. Without benefit of an expanded observation network, it is difficult to separate the effects of the many factors influencing the distribution of precipitation in the region. [ABSTRACT FROM AUTHOR]

Geological research has illustrated the transition of palaeoenvironmental patterns by the earliest Miocene from a planetary-wind-dominant type to a monsoon-dominant type, indicating that the East Asian monsoon became markedly intensified and played a leading role in the East Asian climate. From a modeling point of view, the pioneering research using the reduced number of scenarios had demonstrated that both the Tibetan Plateau uplift and the Paratethys Sea retreat were important for understanding the Asian monsoon evolution. However, the sensitivity of the Paratethys retreat to the East Asian climate still needs further studies based on the more detailed scenarios. Thirty numerical experiments under the six Paratethys Sea and the five Tibetan Plateau conditions illustrate the shifts from zonal climate to the monsoon climate in East Asia. The results confirm again that both the Paratethys retreat and the Tibetan plateau uplift play important roles in the formation of the monsoon-dominant environmental pattern, and show that the Paratethys retreat can strengthen the East Asian monsoon and greatly increase humidity and aridity respectively in the monsoon areas and Northwest China, which is similar to the impact of the Tibetan Plateau uplift on the East Asian climate. Furthermore, the fact that the Paratethys Sea retreats to the Turan Plate is found to be the key criterion for the palaeoenvironmental patterns'' transition in China. The shrinkage of Paratethys Sea leads to the reconstructions of the pressure system and the atmospheric circulations, which result in the variations of precipitation and the transition of palaeoenvironmental patterns. [Copyright &y& Elsevier]

Abstract: Recently, several ice cores were drilled on the Tibetan Plateau to examine climate and environmental changes. Based on the temperature proxy records in the Guliya ice core, climate oscillations over the past 120kyr were examined using wavelet analysis and singular spectrum analysis methods. The results showed two main Milankovitch-type oscillatory modes, 22 and 44kyr. The 22kyr period corresponds to the precession period and 44kyr period corresponds to the Earth axis''s obliquity inclination period. The two periods combined explain ∼43% of the variance. In addition, there are millennial and 10 thousand years time scales periods, which may be related to the Dansgaard–Oeschger (D–O) cycles and the Heinrich (H) events. [Copyright &y& Elsevier]

• Extreme lake level changes (LLCs) occur on Tibetan Plateau in 2015 and 2018. • Mid-summer LLCs robustly connect with subregional rainfall. • The weakened westerlies are critical for 2015. • The strengthened East Asian summer monsoon predominates 2018 rainfall surplus. Previous studies reveal robust lake expansion on TP since the late 1990s. Debate on the quantitative contribution from precipitation and other factors including glacier melting continues, but with more evidence showing that precipitation dominates the interdecadal increase in inner TP lake water storage. However, the TP lake level changes (LLCs) and the potential connection with regional precipitation at interannual timescale and the underlying atmospheric processes, especially for the extreme years, remain unclear yet. The year 2015 and 2018 witness the largest lake level decrease and increase for some major TP lakes during past decades, accompanying extreme rainfall deficit and surplus in mid-summer (July-August) in these two years, respectively. Understanding such extreme hydroclimate events over TP is of great importance for the water resource security in Asia. The central to eastern TP (CETP) is divided into 8 subregions according to the geographical locations of data available lakes and meteorological stations. The mid-summer LLCs on central TP (CTP, subregion II) are robustly and highly related with the concurrent rainfall there, while LLCs on northern central TP (subregion III) are significantly linked to the rainfall over northeastern TP (NETP, subregion VI). The extreme TP lake level decrease and corresponding rainfall deficit in 2015 is closely related to the strong anomalous water vapor divergence, which is mainly induced by weakened westerly winds. Meanwhile, strong wave propagates from the Ural Mountains and North Atlantic to TP and East Asia. In contrast, the extremely high lake level increase and rainfall surplus in 2018 is predominated by easterly winds which are related to the strengthened East Asian summer monsoon. Simultaneously, the western Pacific subtropical high becomes much stronger and extremely northwestward. The CTP rainfall deficit year composite mostly reflects the 2015 case, and NETP rainfall surplus year composite largely resembles the 2018 case, showing similar but weaker atmospheric circulation signals. [ABSTRACT FROM AUTHOR]

An analysis of dust storms and blowing sand records at 681 stations in China during 1961–2000 and in Mongolia during 1980–2000 reveals that the dust source regions in central Asia and the Tibetan Plateau have monthly and interannual northward shifts from the Tibetan Plateau to Mongolia. The monthly shift is closely related to the location of the 200hPa westerly jet and to the location and intensity of the 500hPa westerly jet over central Asia and the Tibetan Plateau. The causes for interannual shifts vary by region. The westerly jet appears to drive the shift on the Tibetan Plateau; the intensity of the central Asian mid-latitude westerly, the Arctic oscillation (AO) and the East Asian winter monsoon may be the drivers in the Hexi Corridor region to the north of the Tibetan Plateau; and the AO and the location of the westerly jet in the Mongolian region. All these causes are closely related to the AO variations, which may provide a connection between climatic changes in East Asia and the North Atlantic, and the long-distance transport of dust. This connection could explain the shifts of dust source regions at interannual and millennial timescales and the roughly synchronous climate changes recorded in the Chinese loess and deep-sea sediments in the North Atlantic Ocean. [Copyright &y& Elsevier]