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The Tibetan Plateau (TP) plays a key role in the water cycle of High Asia and its downstream regions. The respective influence of the Indian and East Asian summer monsoon on TP precipitation and the regional water resources, together with the detection of moisture transport pathways and source regions are subject of recent research. In this study we present a twelve-year high-resolution climatology of the atmospheric water transport (AWT) on and towards the TP, using a new dataset, the High Asia Reanalysis (HAR), which better represents the complex topography of the TP and surrounding high mountain ranges than coarse resolution datasets. We focus on spatio temporal patterns, vertical distribution and transport through the TP boundaries. The results show that the mid-latitude westerlies have a higher share in summertime AWT on the TP than assumed so far. Water vapour (WV) transport constitute the main part, whereby transports of water as cloud particles (CP) play also a role in winter in the Karakoram and western Himalayan regions. High mountain valleys in the Himalayas facilitate AWT from the south whereas the high mountain regions inhibit the AWT to a large extend and limit the influence of the Indian summer monsoon. No transport from the East Asian monsoon to the TP could be detected. Our results show that 40% of the atmospheric moisture needed for precipitation comes from outside the TP, while the remaining 60% are provided by local moisture recycling. How far precipitation variability can be explained by variable moisture supply has to be studied in future research by analysing the atmospheric dynamic and moisture recycling more in detail. [ABSTRACT FROM AUTHOR]

Long‐term decreasing trends of near‐surface wind speed (SWS) have been well demonstrated in China, and at the same time the factors causing the slowdown in SWS have also been explored. However, changes in wind speed and pressure gradient force (PGF) at higher elevations have received little attention. In this paper, the spatio‐temporal changes of wind speed and PGF at different heights were explored in eastern China during the period 1980–2011, and the potential causes inducing the changes of wind speed were analysed. The results included that the reduction in wind speed emerged from the near surface to 300 hPa, while the PGF also exhibited a synchronous reduction. The influence of PGF on the decrease of wind speed was relative smaller at near surface than that at higher levels (850–300 hPa). At the near surface, 71.8% of changes in annual mean SWS could be attributed to the changes of PGF, in which the seasonal difference of the influence of PGF on wind speed was less than 7.0%. At the higher levels, most of the changes in wind speed (>90%) was induced by PGF, in which the seasonal difference of the influence of PGF was less than 1.0%. Furthermore, the changes of PGF in eastern China could be mainly influenced by both the Northern Hemisphere annular mode (NAM) and the Pacific Decadal Oscillation (PDO). The NAM could affect the inter‐annual and inter‐decadal changes of PGF, and the effects of NAM played more significant role on the inter‐annual scale than that on the inter‐decadal scale. At the same time, the correlation between NAM and PGF increased with height. Otherwise, the PDO mainly affected the inter‐decadal changes of PGF, and their correlation decreased with height. [ABSTRACT FROM AUTHOR]

This paper presents the impact of two snow cover schemes (NY07 and SL12) in the Community Land Model version 4.5 (CLM4.5) on the snow distribution and surface energy budget over the Tibetan Plateau. The simulated snow cover fraction (SCF), snow depth, and snow cover days were evaluated against in situ snow depth observations and a satellite-based snow cover product and snow depth dataset. The results show that the SL12 scheme, which considers snow accumulation and snowmelt processes separately, has a higher overall accuracy (81.8%) than the NY07 (75.8%). The newer scheme performs better in the prediction of overall accuracy compared with the NY07; however, SL12 yields a 15.1% underestimation rate while NY07 overestimated the SCF with a 15.2% overestimation rate. Both two schemes capture the distribution of the maximum snow depth well but show large positive biases in the average value through all periods (3.37, 3.15, and 1.48 cm for NY07; 3.91, 3.52, and 1.17 cm for SL12) and overestimate snow cover days compared with the satellite-based product and in situ observations. Higher altitudes show larger root-mean-square errors (RMSEs) in the simulations of snow depth and snow cover days during the snow-free period. Moreover, the surface energy flux estimations from the SL12 scheme are generally superior to the simulation from NY07 when evaluated against ground-based observations, in particular for net radiation and sensible heat flux. This study has great implications for further improvement of the subgrid-scale snow variations over the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

A comprehensive and robust dataset of tropospheric aerosol properties is important for understanding the effects of aerosol–radiation feedback on the climate system and reducing the uncertainties of climate models. The "Third Pole" of Earth (Tibetan Plateau, TP) is highly challenging for obtaining long-term in situ aerosol data due to its harsh environmental conditions. Here, we provide the more reliable new vertical aerosol index (AI) parameter from the spaceborne-based lidar CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) on board CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) for daytime and nighttime to investigate the aerosol's climatology over the TP region during 2007–2020. The calculated vertical AI was derived from the aerosol extinction coefficient (EC), which was rigorously quality-checked and validated for passive satellite sensors (MODIS) and ground-based lidar measurements. Generally, our results demonstrated that there was agreement of the AI dataset with the CALIOP and ground-based lidar. In addition, the results showed that, after removing the low-reliability aerosol target signal, the optimized data can obtain the aerosol characteristics with higher reliability. The data also reveal the patterns and concentrations of high-altitude vertical structure characteristics of the tropospheric aerosol over the TP. They will also help to update and make up the observational aerosol data in the TP. We encourage climate modelling groups to consider new analyses of the AI vertical patterns, comparing the more accurate datasets, with the potential to increase our understanding of the aerosol–cloud interaction (ACI) and aerosol–radiation interaction (ARI) and their climate effects. Data described in this work are available at 10.11888/Atmos.tpdc.300614 (Huang, 2023). [ABSTRACT FROM AUTHOR]

As near-surface wind speed plays a role in regulating surface evaporation and thus the hydrological cycle, it is crucial to explore its spatio-temporal characteristics. However, in-situ measurements are scarce over the Tibetan Plateau, limiting the understanding of wind speed climate across this high-elevation region. This study explores the climatology of near-surface wind speed over the Tibetan Plateau by using for the first time homogenized observations together with reanalysis products and regional climate model simulations. Measuring stations across the center and the west of the plateau are at higher elevations and display higher mean and standard deviation, confirming that wind speed increases with increasing altitude. By exploring wind characteristics with a focus on seasonal cycle through cluster analysis, three regions of distinct wind regimes can be identified: (1) the central Tibetan Plateau, characterized by high elevation; (2) the eastern and the peripheral areas of the plateau; and (3) the Qaidam basin, a topographic depression strongly influenced by the blocking effect of the surrounding mountainous terrain. Notably, the ERA5 reanalysis, with its improvements in horizontal, vertical, and temporal spacing, model physics and data assimilation, demonstrates closer agreement to the measured wind conditions than its predecessor ERA-Interim. It successfully reproduces the three identified wind regimes. However, the newest ERA5-Land product does not show improvements compared to ERA5, most likely because they share most of the parametrizations. Furthermore, the two dynamical downscalings of ERA5 analyzed here fail to capture the observed wind statistics and exhibit notable biases and discrepancies also when investigating the diurnal variations. Consequently, these high-resolution downscaling products do not show add value in reproducing the observed climatology of wind speed compared to ERA5 over the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Previous studies have examined the projected climate types in China by 2100. This study identified the emergence time of climate shifts at a 1◦ scale over China from 1990 to 2100 and investigated the temporal evolution of Köppen-Geiger climate classifications computed from CMIP5 multi-model outputs. Climate shifts were detected in transition regions (7%-8% of China's land area) by 2010, including rapid replacement of mixed forest (Dwb) by deciduous forest (Dwa) over Northeast China, strong shrinkage of alpine climate type (ET) on the Tibetan Plateau, weak northward expansion of subtropical winterdry climate (Cwa) over Southeast China, and contraction of oceanic climate (Cwb) in Southwest China. Under all future RCP (Representative Concentration Pathway) scenarios, the reduction of Dwb in Northeast China and ET on the Tibetan Plateau was projected to accelerate substantially during 2010-30, and half of the total area occupied by ET in 1990 was projected to be redistributed by 2040. Under the most severe scenario (RCP8.5), sub-polar continental winter dry climate over Northeast China would disappear by 2040-50, ET on the Tibetan Plateau would disappear by 2070, and the climate types in 35.9% and 50.8% of China's land area would change by 2050 and 2100, respectively. The results presented in this paper indicate imperative impacts of anthropogenic climate change on China's ecoregions in future decades. [ABSTRACT FROM AUTHOR]

The Third Pole region, especially the Himalayas, is a lightning hotspot. Predicting lightning activity in this region is difficult due to the complex monsoon and westerly circulations, as well as the complex orography. Km-scale simulations can explicitly, without parameterization, tackle deep convective phenomena. A year-long (October 2019–September 2020) ICON-CLM simulation was performed with a km-scale horizontal grid spacing of 3.3 km to assess the region's lightning activity and evaluate the model ICON-CLM. The simulated lightning potential index (LPI) was compared against the lightning proxy CAPE × PREC (CP) derived from ICON-CLM and reanalysis ERA5. In addition, the LPI was evaluated against the TRMM lightning climatology and observed flashes from the International Space Station Lightning Imaging Sensor (ISS-LIS). The LPI reproduced the major spatial, seasonal, and diurnal features of lightning activity as represented in the TRMM climatology. In contrast, the CP from both ICON-CLM and ERA5 performed less well regarding the location of events and the diurnal features. Taking the mean values of the LPI and CP of all the grids within 90 km × 90 km around the ISS-LIS detected lightning event, we found that over 80% of lightning events were recorded using the ICON-CLM simulation. Analysis of individual cases showed that the LPI predicted localization of lightning events better, but flash counts were slightly lower than the CP. Therefore, the combined use of ICON-CLM's simulated LPI and CP can be a valuable predictor for lightning events over the Third Pole region. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamical processes through which the Tibetan Plateau (TP) influences the East Asian summer monsoon (EASM) within the framework of the moist static energy (MSE) budget, using both observations and atmospheric general circulation model (AGCM) simulations. The focus is on the most prominent feature of the EASM, the so-called meiyu-baiu (MB), which is characterized by a well-defined, southwest-northeast elongated quasi-stationary rainfall band, spanning from eastern China to Japan and into the northwestern Pacific Ocean between mid-June and mid-July. Observational analyses of the MSE budget of the MB front indicate that horizontal advection of moist enthalpy, and primarily of dry enthalpy, sustains the front in a region of otherwise negative net energy input into the atmospheric column. A decomposition of the horizontal dry enthalpy advection into mean, transient, and stationary eddy fluxes identifies the longitudinal thermal gradient due to zonal asymmetries and the meridional stationary eddy velocity as the most influential factors determining the pattern of horizontal moist enthalpy advection. Numerical simulations in which the TP is either retained or removed show that the TP influences the stationary enthalpy flux, and hence the MB front, primarily by changing the meridional stationary eddy velocity, with reinforced southerly wind over the MB region and northerly wind to its north. Changes in the longitudinal thermal gradient are mainly confined to the near downstream of the TP, with the resulting changes in zonal warm air advection having a lesser impact on the rainfall in the extended MB region. [ABSTRACT FROM AUTHOR]

Long-term highly accurate surface soil moisture data of TP (Tibetan Plateau) are important to the research of Asian monsoon and global atmospheric circulation. However, due to the sparse in-situ networks, the lack of soil moisture observations has seriously hindered the progress of climate change researches of TP. Based on the Dual-Channel soil moisture retrieval algorithm and the satellite observation data of AMSR-E (Advanced Microwave Scanning Radiometer for EOS), we have produced the surface soil moisture data of TP from 2003 to 2010 and analyzed the seasonal characteristic of the soil moisture spatial distribution and its multi-year changing trend in area of TP. Compared to the in-situ observations, the accuracy of the soil moisture retrieved by the proposed algorithm is evaluated. The evaluation result shows that the new soil moisture product has a better accuracy in the TP region than the official product of AMSR-E. The spatial distribution of the annual mean values of soil moisture and the seasonal variations of the monthly-averaged soil moisture are analyzed. The results show that the soil moisture variations in space and time are consistent with the precipitation distribution and the water vapor transmission path in TP. Based on the new soil moisture product, we also analyzed the spatial distribution of the changing trend of multi-year soil moisture in TP. From the comparisons with the precipitation changing trend obtained from the meteorological observation sites in TP, we found that the spatial pattern of the changing trend of soil moisture coincides with the precipitation as a whole. [ABSTRACT FROM AUTHOR]

Bacteria! abundances in ice cores vary in response to climatic conditions. This paper presents annual bacterial abundances measured in ice deposited over the past 70 years and trapped within a core retrieved from Mount Geladaindong, on the central Tibetan Plateau. The bacterial abundance was lowest in 1938 and highest in 1997. Analyses of correlations between bacterial abundance and δ18O and Ca2+ concentrations indicate that bacterial abundance correlates positively with both temperature and amount of dust transported onto the glacier. These correlations imply that both higher temperatures and more frequent dust deposition influence bacterial abundance in the Geladaindong ice core. Bacterial genetic diversity also changes seasonally, and the diversity during the monsoon season appears much higher than during the nonmonsoon season. Bacterial sequences representing the monsoon season were related to bacteria originating from various environmental conditions while these, representing the nonmonsoon season, were typically related to microorganisms coming from cold environments and soils. [ABSTRACT FROM AUTHOR]

The climatological distribution of mesoscale convective systems (MCSs) over China and its vicinity during summer is statistically analyzed, based on the 10-year (1996-2006, 2004 excluded) June-August infrared TBB (Temperature of black body) dataset. Comparing the results obtained in this paper with the distribution of thunderstorms from surface meteorological stations over China and the distribution of lightning from low-orbit satellites over China and its vicinity in the previous studies, we find that the statistic characteristics of TBB less than -52°C can better represent the spatiotemporal distribution of MCSs over China and its vicinity during summer. The spreading pattern of the MCSs over this region shows three transmeridional bands of active MCSs, with obvious fluctuation of active MCSs in the band near 30°N. It can be explained by the atmospheric circulation that the three bands of active MCSs are associated with each other by the summer monsoon over East Asia. We focus on the diurnal variations of MCSs over different underlying sur- faces, and the result shows that there are two types of MCSs over China and its vicinity during summer. One type of MCSs has only one active period all day long (single-peak MCSs), and the other has multiple active periods (multi-peak MCSs). Single-peak MCSs occur more often over plateaus or mountains, and multi-peak MCSs are more common over plains or basins. Depending on lifetimes and active periods, single-peak MCSs can be classified as Tibetan Plateau MCSs, general mountain MCSs, Ryukyu MCSs, and so on. The diurnal variation of multi-peak MCSs is very similar to that of MCCs (mesoscale convective complexes), and it reveals that multi-peak MCSs has longer life cycle and larger horizontal scale, becomes weaker after sunset, and develops again after midnight. Tibetan Plateau MCSs and general mountain MCSs both usually develop in the afternoon, but Tibetan Plateau MCSs have longer life cycle and more active MαCSs. Ryukyu MCSs generally develop after midnight, last longer time, and also have more active MαCS. The abundant moisture and favorable large-scale environment over Indian monsoon surge areas lead to active MCSs and MαCSS almost at any hour all day during summer. Due to local mountain-valley breeze circulation over the Sichuan Basin, MCSs are developed remarkably more often during the nighttime, and again there are also more active MαCSS. Because of local prominent sea-land breeze circulation over Guangxi and Guangdong, the MCSs over this region propagate from sea to land in the afternoon and from land to sea after midnight. The statistic characteristics of TBB less than -52°C clearly display the different climatological characteristics of MCSs owing to the thermal difference among water, land and rough terrain. Not only the large-scale atmospheric circulation but also the local atmospheric circulation caused by the thermal difference among water, land and rough terrain, to a great extent, determines the climatological distribution of MCSs over China and its vicinity during summer. [ABSTRACT FROM AUTHOR]

The hydrological impact of forest removal on the southeast Tibetan Plateau during the second half of the last century is investigated in this study using an atmospheric general circulation model. The effects of deforestation are investigated by examining the differences between the forest replacement and control experiments. Model results demonstrate that deforestation of the southeast Tibetan Plateau would influence the local and the remote climate as well. It would lead to decreased transpiration and increased summer precipitation in the deforested area and a wetter and warmer climate on the Tibetan Plateau in summer. This may produce more runoff into the rivers originating from the Tibetan Plateau and worsen flooding disasters in the downstream areas. The numerical experiments also show that deforestation would remotely impact Asian climate, and even global climate, although the statistical significance is small. A strong drought is found at middle and lower reaches of the Yellow River, where livelihoods and economics have suffered from recent droughts. Ecosystem research on the Tibetan Plateau is a relatively new topic and needs further interdisciplinary investigation. [ABSTRACT FROM AUTHOR]

In this paper we present results of a numerical study using the NASA finite-volume GCM to elucidate a plausible mechanism for aerosol impact on the Asian summer monsoon involving interaction with physical processes over the Tibetan Plateau (TP). During the pre-monsoon season of March–April, dusts from the deserts of western China, Afghanistan/Pakistan, and the Middle East are transported into and stacked up against the northern and southern slopes of the TP. The absorption of solar radiation by dust heats up the elevated surface air over the slopes. On the southern slopes, the atmospheric heating is reinforced by black carbon from local emission. The heated air rises via dry convection, creating a positive temperature anomaly in the mid-to-upper troposphere over the TP relative to the region to the south. In May through early June in a manner akin to an “elevated heat pump”, the rising hot air forced by the increasing heating in the upper troposphere, draws in warm and moist air over the Indian subcontinent, setting the stage for the onset of the South Asia summer monsoon. Our results suggest that increased dust loading coupled with black carbon emission from local sources in northern India during late spring may lead to an advance of the rainy periods and subsequently an intensification of the Indian summer monsoon. The enhanced rainfall over India is associated with the development of an aerosol-induced large-scale sea level pressure anomaly pattern, which causes the East Asia ( Mei-yu) rain belt to shift northwestward, suppressing rainfall over East Asia and the adjacent oceanic regions. [ABSTRACT FROM AUTHOR]

This paper reviews recently published literature, most of which was published in Chinese, and searches for regional patterns of Holocene changes useful in depicting global patterns. The Holocene in the Xinjiang region can be divided into three stages: a warming and dry early stage (from 11 ∼ 10 to 8 ∼ 7 ka BP), a warm and wet middle stage (from 8 ∼ 7 to 4.5 ∼ 3 ka BP) and a fluctuating cool and dry late stage (since 4.5 ∼ 3 ka BP). The Holocene in the northern Tibetan Plateau can also be divided into three stages: a warming and wet stage (from 10.5 ∼ 10 to 5 ∼ 4 ka BP), followed by a variable drying and probably warm stage (5 ∼ 4 to 3 ka BP) and ending with a cool and dry stage (since 3 ka BP). In the Inner Mongolian Plateau, the early Holocene (from 10.5 ∼ 9.5 to 8 ∼ 7.5 ka BP) was warming and dry, and a warm and wet climate occurred from 7.5 to 3.5, during which the best time was 6.3–3.8 ka BP; the climate has been variably drying and probably cooling since 3.5 ka BP. In the northwestern part of the Loess Plateau, several Holocene palaeosols have been identified (10–9, 7.5–5, 4–3 and 2.7–2 ka BP) with the 7.5–5 ka BP palaeosol being most strongly expressed. The best-developed palaeosol-equivalent in major valleys is a swamp-wetland facies deposited between 8885 and 3805 14C yr BP under an extremely wet regime. The climate has fluctuated significantly at least three times around a dry and probably cool regime after the swamp-wetland facies-depositional period. Our summary shows that the Holocene Climatic Optimum occurred nearly contemporaneously (8–5 ka BP) at all sites in the Xinjiang region, in the Inner Mongolian Plateau and in the northwestern part of the Loess Plateau. A warming and wet early Holocene (10–8 ka BP) in the northern Tibetan Plateau is most likely related to high effective soil moisture resulting from snow and ice melting. We propose here that the middle Holocene Climatic Optimum (8–5 ka BP) in arid to semi-arid China was primarily a delayed response of the low latitude oceans to high latitude peak insolation (9–8 ka BP). [ABSTRACT FROM AUTHOR]

Atmospheric simulation-based gridded precipitation datasets have been widely used in hydrological and land surface modeling, but may contain larger uncertainties in mountainous regions. This study compared the performance of the fifth European Centre for Medium-Range Weather Forecasts reanalysis (ERA5) precipitation data with two fused precipitation datasets [China Meteorological Administration Land Data Assimilation System version 2.0 (CLDAS2.0) and China Meteorological Forcing Dataset (CMFD)] in the Yarlung Zangbo River basin (YZRB), which has a complex terrain and climate. Compared to in situ observations, ERA5 could capture the spatial--temporal pattern of precipitation but showed high precipitation, especially in the downstream region (lower Nuxia discharge station). In terms of the correlation coefficient, the overall performance of the ERA5 data was slightly worse than that for CMFD data at both the monthly and yearly scales, and was comparable to that of the CLDAS2.0 data. Given that the spatial mismatch between the gridded and in situ data may influence the evaluation, we also employed the water balance method to constrain basinwide precipitation amounts. We found that CLDAS2.0 and CMFD precipitation data tended to cause long-term water imbalance, and ERA5, with a much larger multiyear average annual precipitation, could better close the water budget. Further analysis showed that the differences in multiyear average annual precipitation between ERA5 and in situ observations were closely related to the slope and standard deviation of the subgrid-scale orography, indicating the substantial influence of subgrid topography on precipitation simulation. These findings highlight that ERA5 could be a potential reference dataset for hydrological modeling of the YZRB. [ABSTRACT FROM AUTHOR]

To aid the understanding of atmospheric circulation climatology over the Tibetan Plateau (TP), this study investigated the comprehensive potential vorticity (PV) budget over the TP using model‐level reanalysis data. Our findings demonstrate the effects of diabatic heating, friction, gravity wave drag, advection, and convection in determining circulation over the TP, from the PV budget perspective. In summer, the diabatic heating‐generated positive (negative) PV tendency facilitates cyclonic (anticyclonic) circulation near the surface (in the middle troposphere). Low PV in the upper troposphere, pertaining to the Asian monsoon anticyclone and monsoonal overturning circulation is induced by the upward transportation of diabatic heating‐generated low PV in the middle troposphere. Horizontal advection further spreads the low PV—that is vertically inputted from the middle troposphere—to a wide area around the TP in the upper troposphere. In winter, the diabatic heating‐generated positive PV near the surface is balanced by the sinking motion‐carried low PV. In addition, gravity wave drag‐generated PV is prominent in the upper troposphere in winter and can affect the downstream climate through advection. We further revealed the crucial role of the diurnal cycle in shaping the near‐surface cyclonic circulation in summer by regulating the vertical structure of diabatic heating. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau Vortex (TPV) is an important low-pressure system that affects the weather and climate in the Qinghai-Tibet Plateau. It is of great importance to study the water cycle of the TPV to further understand the TPV and its resulting disastrous weather. This study is different from the previous studies of TPV cases or of the atmospheric water cycle of the Qinghai Tibet Plateau. Focusing on the moving TPV weather system, from the perspective of climatology, the characteristics of the atmospheric water cycle of the TPV and the atmospheric circulation that affects the activity of the TPV water cycle are studied using statistical methods based on the reanalysis data. The results show that the TPV water cycle is mainly affected by external circulation. The overall water vapour utilization efficiency of the TPV water cycle first decreases and then increases, and its activity degree first decreases and then increases. The high-value area of TPV precipitation is located in the middle of the plateau and annual TPV precipitation has a good correlation with TPV water cycle activity. The large-scale system is closely related to the vortex water cycle of the plateau. When the intensity of the South Asian high (SAH) is relatively strong, the West Pacific subtropical high (WPSH) advances westward, and there is a stronger warm rising area over the main body of the plateau. When the southerly airflow on the south side of the low-level plateau is strong, the water cycle of the TPV is more active, easily moves eastward and produces more precipitation, and vice versa. [ABSTRACT FROM AUTHOR]

Thundersnow is a special kind of thunderstorm that combines snowfall and lightning. A 10‐year thundersnow climatology over China was obtained based on observations during 2008–2017. Our results show that thundersnows are widely distributed in China, and most of the high‐frequency areas are located in the Tibetan Plateau and northeastern China. The average frequency of thundersnow decreases with decreasing altitude, and thundersnow usually occurs at low‐altitude stations once every 10 years. Thundersnow, which likely induces great total snowfall depths, appears mostly in spring, autumn and late winter and can occur in high‐altitude areas in summer. The blizzard probability on a thundersnow day is 12.7%. The percentage of positive cloud‐to‐ground lightning of winter thundersnow is approximately 20.7%, which is lower than those in other seasons. The negative phase of the Arctic Oscillation and anomalous western North Pacific anticyclone are favorable background conditions for thundersnow events. Plain Language Summary: Though the snowfall process is different from common rainfall processes that are accompanied by lightning, it can also occasionally produce lightning. This special type of thunderstorm is called thundersnow. It can induce heavy snowfall, which results in partial paralysis of modern cities. Electrified winter clouds may pose an aviation hazard. Although the frequency of thundersnow is low, it is widely distributed in China. Thundersnow can occur throughout the year, mainly in February‐May and October‐November. Thundersnow events increase the probability of blizzards, especially in the Shandong Peninsula in spring, North China and the Changbai Mountain in autumn, and the middle and lower reaches of the Yangtze River basin and Bohai Rim in winter. The variations of the thundersnow number are closely associated with extratropical atmospheric circulation anomalies. The climatological and atmospheric conditions of thundersnow in China that are revealed by this study help establish an important basis for thundersnow forecasting. Key Points: A 10‐year climatology of thundersnow in China was revealed for the first timeThe high‐frequency areas of thundersnow are mainly located in the Tibetan Plateau and northeastern ChinaThundersnow is significantly influenced by the Arctic Oscillation and associated with the anomalous western North Pacific anticyclone [ABSTRACT FROM AUTHOR]

Serving as the successor to the ERA‐Interim dataset, a new global reanalysis (i.e., ERA5) has been released by the European Centre for Medium‐Range Weather Forecasts. However, evaluation of the performance of ERA5 in relation to the Tibetan Plateau (TP) remains lacking. Using in situ eddy covariance observations from eight stations located on the TP, this study evaluated the uncertainties of both ERA5 and ERA‐Interim. Results showed that ERA5 effectively corrects the overestimation of both sensible heat flux (H) and latent heat flux (LE) over the TP, which is severe in ERA‐Interim. In most seasons, the bias errors (BEs) of H and LE are generally smaller in ERA5 than in ERA‐Interim, although the BEs of wintertime H and LE in spring and autumn are not decreased significantly from ERA‐Interim to ERA5. The spatiotemporal relationships with the Global Land Data Assimilation System (GLDAS) and the Global Land Evaporation Amsterdam Model (GLEAM) reanalysis data were investigated. Analysis of correlation coefficients and root mean squared errors revealed large inconsistency in H between ERA5/ERA‐Interim and GLDAS, but good agreement in LE between ERA5/ERA‐Interim and GLEAM. Overall, the level of agreement of ERA5 with GLEAM was better than that of ERA‐Interim. Anomaly correlation coefficients (ACCs) between the two ERA datasets (ERA5 and ERA‐Interim) and the two reference datasets (GLDAS and GLEAM) were also investigated. The ACC results further confirmed that ERA5 has better agreement than ERA‐Interim with GLEAM in terms of LE over the TP. [ABSTRACT FROM AUTHOR]

Changes in vegetation dynamics play a critical role in terrestrial ecosystems and environments. Remote sensing products and dynamic global vegetation models (DGVMs) are useful for studying vegetation dynamics. In this study, we revised the Community Land Surface Biogeochemical Dynamic Vegetation Model (referred to as the BGCDV_CTL experiment) and validated it for the Tibetan Plateau (TP) by comparing vegetation distribution and carbon flux simulations against observations. Then, seasonal–deciduous phenology parameterization was adopted according to the observed parameters (referred to as the BGCDV_NEW experiment). Compared to the observed parameters, monthly variations in gross primary productivity (GPP) showed that the BGCDV_NEW experiment had the best performance against the in situ observations on the TP. The climatology from the remote sensing and simulated GPPs showed similar patterns, with GPP increasing from northwest to southeast, although the BGCDV_NEW experiment overestimated GPP in the semi-arid and arid regions of the TP. The results show that temperature warming was the dominant factor resulting in the increase in GPP based on the remote sensing products, while precipitation enhancement was the reason for the GPP increase in the model simulation. [ABSTRACT FROM AUTHOR]

Investigated in this study are the seasonal and semi‐diurnal variations of the cloud‐phase climatology over the southern Himalayas and adjacent regions by using 5 years of Himawari‐8 cloud‐product data (2016–2020). The four selected regions from south to north are the Gangetic Plains (I), Himalayan foothills (II), southern slope of the Himalayas (III), and the Himalayan–Tibetan Plateau region (IV), respectively. Results showed that the cloud frequency of cloud gradually increases from region I via II to III, then sharply decreases as the altitude increases up to IV. Ice‐phase clouds occurs more frequently over regions I/II (III/IV) during boreal summer (winter), while water‐phase cloud has a higher frequency over region III/IV (I/II) in summer (winter), respectively. All of the different cloud phases have a clear seasonal cycle. Furthermore, the semi‐diurnal variation shows that water‐phase clouds tends to have an occurrence frequency peak around noon (in the later afternoon) over regions I/II/III in summer (winter), whereas over region IV it only occurs more in the morning in both seasons. Ice‐phase cloud generally occurs more in the late afternoon in both boreal summer and winter, especially over region IV. Further analysis showed that the differences in the cloud‐phase characteristics over the southern Himalayas and adjacent regions are likely related to the interactions of the synoptic‐scale circulation, the topography, and the water vapor transport. Plain Language Summary: By using 5 years geostationary weather satellite cloud product, we investigated the seasonal and semi‐diurnal variations of the cloud‐phase climatology characteristics over the southern Himalayas and adjacent regions, including four select sectors of the plain, foothill, slope and plateau. We found that the cloud frequency gradually increases from plain via foothill to slope, then decreases as the terrain increases up to plateau. All different phase clouds have a clear seasonal cycle and semi‐diurnal variations. Such as ice‐phase cloud occurs more over the plain and the foothill during summer season, while it occurs more over the slope region and plateau in winter; water‐phase cloud has a peak at noon (later afternoon) over the plain/foothill/slope in summer (winter), while over the plateau, it only occurs more in the morning. The results are important for comprehend how the southern Himalayas impact regional climate. Key Points: Cloud frequency increases significantly from region I via II to III, then decreases as the elevation further increases up to region IVIce‐phase clouds occurs more frequently over regions I/II (III/IV) in summer (winter), which is opposite to the occurrence of water‐phase cloudWater‐phase clouds tend to occur more around noon (in the later afternoon) over regions I/II/III in summer (winter), while it only occurs more in the morning over region IV [ABSTRACT FROM AUTHOR]

The eight datasets of the summer (June-August) surface sensible heat (SH) flux over the Tibetan Plateau (TP) are compared on the time scales of the climatology, interannual variability and linear trend during 1980-2006. These data sets include five reanalyses (National Center for Environmental Prediction reanalysis, NCEPR1 and NCEPR2, NCEP climate forecast system reanalysis, CFSR, Japanese 25-year reanalysis, JRA, and European Centre for Medium Range Weather Forecasts reanalysis, ERA40), two land surface model outputs (Noah model data of Global Land Data Assimilation System version 2, G2_Noah, and Simple Biosphere version 2 output by Yang et al., YSiB2), and estimated SH based on China Meteorological Administration (CMA) station observations, ObCh. The results suggest that the summer SH on the TP differs from one dataset to another due to different inputs and calculations. Climatologically, the ERA40 and JRA distribute rather uniformly while the other six products show similar regional disparities, that is, larger in the west than in the east and stronger in the north and the south than in the middle of the plateau. The mean magnitude of the SH averaged over the 76 stations above the TP varies considerably among each dataset with the difference of more than 20 W m between the maximum (G2_Noah) and minimum (ObCh). Nevertheless, they are consistent in the interannual variability and mostly show a significant decreasing trend corresponding to the weakening surface wind speed, in spite of the distinct trend for the ground-air temperature difference among the different data sets. These two consistencies indicate the particular availability of the SH products, which is helpful to the relevant climate dynamics research. [ABSTRACT FROM AUTHOR]

The Zhada basin is a large Neogene extensional sag basin in the Tethyan Himalaya of southwestern Tibet. In this paper we examine environmental changes in the Zhada basin using sequence stratigraphy, isotope stratigraphy, and lithostratigraphy. Sequence stratigraphy reveals a long-term tectonic signal in the formation and fi lling of the Zhada basin, as well as higher-frequency cycles, which we attribute to Milankovitch forcing. The record of Milankovitch cycles in the Zhada basin implies that global climate drove lake and wetland expansion and contraction in the southern Tibetan Plateau from the Late Miocene to the Pleistocene. Sequence stratigraphy shows that the Zhada basin evolved from an overfi lled to underfi lled basin, but continued evolution was truncated by an abrupt return to fl uvial conditions. Isotope stratigraphy shows distinct drying cycles, particularly during times when the basin was underfi lled. A long-term environmental change observed in the Zhada basin involves a decrease in abundance of arboreal pollen in favor of nonarboreal pollen. The similarity between the long-term environmental changes in the Zhada basin and those observed elsewhere on and around the Tibetan Plateau suggests that those changes are due to global or regional climate change rather than solely the result of uplift of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Desertification in Qinghai-Xizang (Tibet) Plateau is part of Chinese desertification. In the past decades, due to the climate warming, the climate condition in Qinghai-Xizang (Tibet) Plateau has been relatively dry. This has resulted in permafrost degradation and other environmental problems. In addition, the vegetation and the soil layer were also destroyed by unreasonable economic activities. Cultivated and grassland lands have become deserted. Nowadays, the desertification is still expending. In this paper, the factors affecting the desertification in Qinghai-Xizang (Tibet) Plateau were examined, and the desertification as well as its relationship with permafrost degradation was also discussed. [Copyright &y& Elsevier]

The frequently observed tropospheric warm cores over the Tibetan Plateau (TP) are unique climate phenomena and are crucial to the Asian summer monsoon development. However, their climatological structure and formation mechanisms remain elusive and inconsistent among previous studies. In this work, two vertically separated warm cores, the upper-level warm cores (ULWCs) and lower-level warm cores (LLWCs), are identified based on the zonal temperature deviation. The LLWCs are basically confined below 450 hPa, and the ULWCs are mostly observed at 200–400 hPa. The active region of the LLWCs is generally within the TP domain and characterized by regional patches with high frequency occurrences. In contrast, the active region of the ULWCs is featured by a zonally elongated band along the southern TP. The physical mechanisms for the formations of these two distinct types of warm cores are revealed: the LLWCs are mainly generated and maintained by the surface diabatic heating, while the ULWCs are dominated by the large-scale circulation associated with the convection over the Indo-Pacific warm pool. During March–June, the ULWCs within the TP domain occur most frequently and the intensities attain their maxima. In March–April, the ULWCs are mainly determined by the TP adiabatic subsidence induced by the convection over the Indo-Pacific warm pool. In May–June, the warm advection induced by westerlies generates the downstream ULWCs and enhances the ULWCs formed in previous months. Hence it might be inappropriate in traditional view to attribute the tropospheric warm cores around the TP solely to the direct thermal effect of the elevated topography. [ABSTRACT FROM AUTHOR]

Dust aerosol can affect the atmospheric thermal structure and exert great melting potential on snow and ice sheets. In this study, the decadal climatology of dust‐forced radiative heating (DRH) in the atmosphere over Tibetan Plateau and its surroundings (TPS) was investigated using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model along with the CALIPSO satellite observations from 2007 to 2016. After screening out other aerosols, the vertical distribution of dust aerosol was examined to accurately assess the DRH. The net DRH showed a significant warm effect mainly by dust loading, which covers from the center of dust sources to their adjacent transport regions. The maximum value of the DRH appeared at the near‐surface, while the DRH decreased with an increase in height. The climatic average DRH at the near‐surface reached 16.8 K/month at the Taklimakan Desert (TD) and 10.8 K/month at the Gangetic Plain in spring, 13.7 K/month at the Indus Plain in summer, which is 3–3.6 times warmer than the column‐averaged DRHs. This study also found the most significant influence of dust events on the Qaidam Basin in the TPS, in which the near‐surface DRH was 4.7 K/month during spring. It is also noteworthy that the intermonth and interannual variations of the DRH highlighted the significant warming effect of dust aerosols on the atmospheric thermal structure, especially at the near‐surface. In addition, we need to pay more attention to changes in snow‐related processes influenced by absorbing aerosols and the light‐absorbing impurities deposited in snow over the TPS. Key Points: Dust‐forced radiative heating (DRH) has a significant warming effect with the center from dust sources to adjacent transport regionsThe near‐surface DRHs over the Tibetan Plateau and its surroundings (TPS) are 3–3.6 times larger than the column‐averaged valueDust aerosols over the TPS may have the potential to exert more snow melting driven by the remarkable near‐surface warming effect [ABSTRACT FROM AUTHOR]

The Eocene was the initial stage of the Cenozoic global climatic transition from greenhouse to icehouse conditions. Our understanding of the Eocene climate is based mainly on marine records, and comparison of marine and terrestrial climate records of the Eocene has revealed inconsistencies. Thus, there is a need for more continuous, high‐resolution Eocene sedimentary records from land. Xining Basin in the northeastern Tibetan Plateau contains a sequence of well‐exposed and complete Eocene strata. Extending previous research, we have conducted a new high‐resolution lithostratigraphic and magnetostratigraphic study of the Xijigou section in Xining Basin. The results indicate that the Xijigou section spans the interval from ~34.2 to 53 Ma, representing an average sediment accumulation rate of ~1.4 cm/kyr. The basal ages of the Mahalagou and Honggou Formations are ~39.9 and ~52.4 Ma, respectively. A comparison of all available Eocene sedimentary records from Xining Basin indicates that the strata deposited during ~53–35 Ma developed conformably and are well correlated over space. We conclude that sediment deposition was not affected by large‐scale tectonic activity at the time and rather was controlled by the global climate. After ~35 Ma, the sediment accumulation rate increased to ~4 cm/kyr, which may reflect the far‐field influence of the India‐Eurasia collision on Xining Basin. Key Points: A new high‐resolution lithostratigraphy and magnetostratigraphy of Eocene terrestrial sediments in Xining BasinA synthesis of the Eocene magnetostratigraphic framework in Xining Basin via basin‐wide stratigraphic correlationDuring ~53‐35 Ma, there was minimal tectonic influence and sediment accumulation was uniform in Xining Basin [ABSTRACT FROM AUTHOR]

To assess the recent warming on the Tibetan Plateau (TP), some tree‐ring‐based temperature reconstructions have been performed. However, most of the previous studies focused on the local or regional scale. In this study, we analyzed the recent variability of August‐September temperature using observations from 79 TP meteorological stations, and the observed records were extended back to 1,572 based on a tree‐ring maximum density network comprising 17 sites. Moreover, the future August‐September temperature scenarios on the TP are also presented using the ensemble mean of five regional climate models. The tree‐ring maximum late‐wood density network shows good capacity to reconstruct the August‐September temperature variability at the spatial scale of the whole TP (i.e., 79‐station average; r1951–2014 = 0.80, P < 0.01). The reconstruction suggests that the instrumental epoch is the warmest interval of August‐September over the past four and a half centuries on the TP, and the decadal‐scale August‐September warming since the 1960s is unprecedented. The ensemble simulation of five regional climate models indicates that persistent August‐September warming will occur on the TP in the future. The magnitude of August‐September warming is approximately 1.56 ± 0.30°C and 3.02 ± 0.29°C over the period 2006–2049 under the Representative Concentration Pathways (RCPs) 4.5 and P8.5 scenarios, respectively. These results imply a further ecological and environmental change on the TP linked to the persistent warming in the future. Key Points: Significant August‐September warming occurred over the Tibetan Plateau (TP) during the instrumental periodThe instrumental epoch is the warmest interval of August‐September since 1572 on the TPThe increase in August‐September mean temperature will likely exceed 2°C above preindustriallevels until the mid-21st century on the TP [ABSTRACT FROM AUTHOR]

This study implements a variable resolution version of Community Earth Systems Model (VR‐CESM; regionally refined at 1/8° resolution) to assess the improvement in simulating the seasonal climate across the Tibetan Plateau (TP) at higher horizontal resolutions compared to its uniform (UN) 1° counterpart (UN‐CESM). The Weather Research and Forecasting (WRF) model, run at 12‐km horizontal grid spacing, is compared to both CESM simulations. VR‐CESM and WRF are more comparable to satellite and surface‐based observations than UN‐CESM in simulating summertime (June to August) temperature across the TP and TP foothills, respectively. WRF and VR‐CESM also more accurately simulate precipitation than UN‐CESM across the region due to more accurate terrain treatment. The number of days in which effective (>2.5 mm/day) and heavy (>25 mm/day) precipitation events are generally better captured in VR‐CESM compared to UN‐CESM and WRF. Finally, snow cover fraction in VR‐CESM is better simulated for all months compared to UN‐CESM, with the largest improvements simulated from June to August, while WRF performs even better than VR‐CESM in simulating snow cover fraction. The improvements in simulated temperature, precipitation, and snow cover are due to WRF and VR‐CESM's ability to resolve more complex topographic features rather than time step differences between the UN‐CESM and VR‐CESM experiments. While it is fairly intuitive that improved topography accuracy should bring forth more accurate simulated meteorology, this evaluation suggests that VR‐CESM is competitive or may even be preferred over regional climate models (such as WRF) when examining internal and external climate variability, as it bypasses several drawbacks associated with regional climate models. Key Points: VR‐CESM more accurately captures Tibet's heterogeneous temperature, precipitation, and snow fields compared to tradition 1‐degreee CESMImprovements in simulated meteorology are brought about by better‐resolved mesoscale circulations, which regulate the surface energy budgetVR‐CESM better simulates moisture convergence and precipitation across Nepal, compared to 1‐degree CESM [ABSTRACT FROM AUTHOR]

Based on the observed rainfall data at 34 stations over the Tarim Basin (TB) and the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data during 1961–2012, the concurrent effects of the plateau monsoon (PM) over the Tibetan Plateau and the South Asian monsoon (SAM) on summer rainfall over the TB are investigated. Mid‐upper tropospheric temperature (MUTT) plays an important role in linking the PM and the SAM with summer rainfall over the TB. The concurrent influential mechanisms of the PM and the SAM on summer rainfall over the TB can be summarized as follows. The strengthened (weakened) PM and the weakened (strengthened) SAM cause mid‐upper tropospheric cooling (warming), which tends to result in the migration of the subtropical westerly jet further southward (northward). Then an anomalous southerly (northerly) flow prevails over the TB, and more (less) water vapour is transported into the TB by a two‐step process. All above contribute significantly to an increase (decrease) in the occurrence of summer rainfall over the TB. In addition, we also discuss the relative contribution of the PM and the SAM to summer rainfall over the TB. Partial correlations show that the PM and the SAM can both individually influence summer rainfall over the TB. The PM has a direct effect on summer rainfall over the TB, for its considerable relations not only with MUTT but also with atmospheric circulation. Whereas the SAM has an indirect effect for its only influence on MUTT, which then give rise to an anomalous circulation related to summer rainfall over the TB. Locations of the observational stations (dots) and the climatological characteristics of summer rainfall (contours, mm) over the Tarim Basin. Shaded areas indicate terrain height. [ABSTRACT FROM AUTHOR]

Circulation‐type classifications (CTCs) are useful tools for systematically describing atmospheric circulation and studying its variation and impact on surface climate. However, few circulation classification methods (CCMs) have been applied in the Tibetan Plateau (TP). In this study, six frequently used CCMs using 500 hPa geopotential height data were assessed with respect to their abilities in explaining observed daily mean temperature and precipitation variations in the central and eastern TP for the period 1980–2014. Two statistical measures, the explained variance and the Kolmogorov–Smirnov test, were used to quantify the performance of the CTCs in describing climate variable variations. SAN (simulated annealing and diversified randomization clustering) and KRZ (Kruizinga's eigenvector‐based scheme) were identified as optimum CCMs for synoptic typing over the study region. The daily mean temperatures are well conditioned on SAN‐CTC with 43.9–62.4% explained variance at annual scale and 11.1–25.2% at seasonal scale. For daily precipitation variations, the explained variance at the annual scale is less than 40%. The spatial characters of climate variation affected by large‐scale circulation are identified. Daily mean temperature variations in the Qaidam Basin and the Qilian Mountains (90°–103°E and 35°–40°N) all year round and in the region between the Tanggula Mountains and the Himalayan Mountains (88°–97°E and 30°–34°N) in wet season (May–September) are well resolved by the CTCs. Daily precipitation variations in the eastern TP in the dry season (October–April) and a region from the Brahmaputra River basin to the Tanggula Mountains (85°–92°E and 28°–32°N) and the southern Hengduan Mountains (98°–102°E and 27°–31°N) in the wet season show a close relationship with the identified CTCs by SAN. Schematic diagram of the circulation systems related to TP climate variations. The boundaries of the four spatial domains for circulation classification are drawn with different kinds of dashed lines (domain 1: 40°–135°E, 5°S–70°N, domain 2: 50°–125°E, 5°–60°N, domain 3: 60°–115°E, 15°–50°N, domain 4: 70°–105°E, 25°–40°N). [ABSTRACT FROM AUTHOR]

Based on the European Centre for Medium‐Range Weather Forecasts (ECMWF) ERA‐Interim reanalysis data from 1979 to 2016, an index for Tibetan Plateau (TP) soil moisture (ITPSM), which could represent inter‐annual variation in spring soil moisture, is defined after removing the linear trend in soil moisture. The late spring soil moisture variation over the TP and its influences on the plateau summer monsoon are analysed. The results show that the TP soil moisture variation is non‐uniform, and spring soil moisture over the northeastern TP shows an increasing trend, while the western TP (especially the peripheral area) renders a significantly decreasing trend. When the ITPSM shows positive (negative) anomalies (i.e., spring soil moisture over the northeastern TP is higher (lower), soil moisture over the western TP is lower (higher) than normal), the plateau summer monsoon may be stronger (weaker). Anomalous variations in spring TP soil moisture can eventually affect the plateau summer monsoon by changing atmospheric circulation, diabatic heating, and water vapour transportation. It is found that when the ITPSM exhibits positive anomalies, diabatic heating over the centre and eastern TP is remarkably enhanced, and warm and humid moisture from the Bay of Bengal and Arabian Sea and cold air from high latitudes merge over the central and eastern TP; coupled with lower‐level convergence and upper‐level divergence, all these contribute to an increase in plateau summer monsoonal precipitation. When the ITPSM shows negative anomalies, diabatic heating over the centre and eastern TP is weakened, the anomalous cyclone to the south of the TP hinders warm and humid air flows transportation to the TP, and the anomalous anticyclone to the southeast of Lake Baikal weakens cold air to the south; coupled with weakened convergence and upwards motion, these factors all lead to a decrease in plateau summer monsoonal precipitation. [ABSTRACT FROM AUTHOR]

Variations of surface air temperature (SAT) are key in affecting the hydrological cycle, ecosystems and agriculture in western China in summer. This study assesses the seasonal forecast skill and reliability of SAT in western China, using the GloSea5 operational forecast system from the UK Met Office. Useful predictions are demonstrated, with considerable skill over most regions of western China. The temporal correlation coefficients of SAT between model predictions and observations are larger than 0.6, in both northwestern China and the Tibetan Plateau. There are two important sources of skill for these predictions in western China: interannual variation of SST in the western Pacific and the SST trend in the tropical Pacific. The tropical SST change in the recent two decades, with a warming in the western Pacific and cooling in the eastern Pacific, which is reproduced well by the forecast system, provides a large contribution to the skill of SAT in northwestern China. Additionally, the interannual variation of SST in the western Pacific gives rise to the reliable prediction of SAT around the Tibetan Plateau. It modulates convection around the Maritime Continent and further modulates the variation of SAT on the Tibetan Plateau via the surrounding circulation. This process is evident irrespective of detrending both in observations and the model predictions, and acts as a source of skill in predictions for the Tibetan Plateau. The predictability and reliability demonstrated in this study is potentially useful for climate services providing early warning of extreme climate events and could imply useful economic benefits. [ABSTRACT FROM AUTHOR]

The dynamics of basin-scale water budgets over the Tibetan Plateau (TP) are not well understood nowadays due to the lack of in situ hydro-climatic observations. In this study, we investigate the seasonal cycles and trends of water budget components (e.g. precipitation P, evapotranspiration ET and runoff Q) in 18 TP river basins during the period 1982-2011 through the use of multi-source datasets (e.g. in situ observations, satellite retrievals, reanalysis outputs and land surface model simulations). A water balancebased two-step procedure, which considers the changes in basin-scale water storage on the annual scale, is also adopted to calculate actual ET. The results indicated that precipitation (mainly snowfall from mid-autumn to next spring), which are mainly concentrated during June-October (varied among different monsoons-impacted basins), was the major contributor to the runoff in TP basins. The P, ET and Q were found to marginally increase in most TP basins during the past 30 years except for the upper Yellow River basin and some sub-basins of Yalong River, which were mainly affected by the weakening east Asian monsoon. Moreover the aridity index (PET=P ) and runoff coefficient (Q=P) decreased slightly in most basins, which were in agreement with the warming and moistening climate in the Tibetan Plateau. The results obtained demonstrated the usefulness of integrating multi-source datasets to hydrological applications in the data-sparse regions. More generally, such an approach might offer helpful insights into understanding the water and energy budgets and sustainability of water resource management practices of data-sparse regions in a changing environment. [ABSTRACT FROM AUTHOR]

The Late Cenozoic East Asian winter monsoon (EAWM) enhancement has been attributed to several factors, such as uplift of the Tibetan Plateau, retreat of the Paratethys Sea, and global cooling related to polar ice volume increment. However, the fundamental forcing factors remain enigmatic due to the absence of long and continuous climate records and sensitive indicators. Here we reanalyzed the published grain-size record of Sikouzi fine sediments in the western Chinese Loess Plateau through end-member (EM) modeling. The results indicate that EM 2 with grain-size peaks between 10–100 μm decreased in content from 20.1 to 17 Ma and stepwise increased from 17 to 0.07 Ma during the following six stages (17–15 Ma, 15–12 Ma, 12–8 Ma, 8–6 Ma, 6–4 Ma and 4–0 Ma). Such varying trends can be successively correlated in seven stages with the integrated benthic δ18O record, implying that global warming weakened the EAWM from 20.1 to 17 Ma and global cooling has stepwise strengthened the EAWM since 17 Ma. Therefore, we conclude that global temperature change played a major role on the evolution of EAWM during the Neogene period. By contrast, Late Cenozoic palaeogeographic reorganization caused by uplift of the Tibetan Plateau and retreat of the Paratethys Sea contributed less to the evolutionary evolution of EAWM. Spectral analysis of the EM 2 data first provided direct evidence of orbitally influenced deposition in the study area and thus the EAWM variations during the Neogene period. The 100-kyr period became weak since ~10 Ma, possibly due to the decrease in sensitivity of a more stable, continental-scale ice sheet in Antarctica to local insolation forcing, deserving further investigation. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) experienced a rapid warming and wetting in recent decades. The elevation dependence of warming rate has been established, while the question of trend in precipitation against the elevation gradient remains open. By using the in situ observation of precipitation, air temperature, and surface specific humidity from 91 stations over and around the TP, this study investigated how the trends in summer precipitation varied along the elevation gradient over and around the TP during the period 1970-2014. The major findings are as follows: (1) the trends in summer precipitation from 1970 to 2014 displayed an increasing tendency at a rate of 0.83% decade-1 km-1 with the increased elevation, and the rate for 1991–2014 (2.23% decade-1 km-1) is even greater and (2) the temporal trends in surface air temperature, surface specific humidity (surface water vapour) from in situ observations and total column of water vapour from Japanese 55-year reanalysis (JRA-55) data overmost stations consistently display similar elevation dependence, which provides a plausible explanation for the elevation dependence of the summer precipitation trends based on the Clausius–Clapeyron relationship. The large-scale atmospheric circulations are other possible factors influencing the elevation dependence of summer precipitation trends, which needs further investigations. [ABSTRACT FROM AUTHOR]

We use the output of twenty-seven Global Climate Models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5) to investigate the temperature changes and their dependence on the elevation in the Tibetan Plateau, Himalaya and Karakoram mountains and in the surrounding areas in historical model simulations and in future projections. The aim of this study is to explore if and to what extent the CMIP5 models show elevation-dependent warming (EDW) in this part of the globe and to investigate what are the driving factors at play and their relative importance. Our results indicate that the models show enhanced rates of warming at higher elevations in the Tibetan Plateau-Himalayan region in the twentieth century, and this phenomenon is projected to strengthen by the end of the twenty-first century under a high-emission scenario. We find a nonlinear relationship between the warming rates and the elevation, for both the minimum and the maximum temperature: regions with temperatures below the freezing level of water show more warming than the regions with temperatures above, likely suggesting a key role of mechanisms involving water phase changes, the presence/absence of snow and the snow-albedo feedback. We consider the main variables simulated by the CMIP5 models whose change may be related to temperature changes at higher elevations. We find that changes in surface albedo, atmospheric humidity and downward longwave radiation are relevant factors for EDW in the Tibetan Plateau-Himalayas, with surface albedo being the leading driver. [ABSTRACT FROM AUTHOR]

Phylogeographical studies have suggested that several plant species on the Tibetan Plateau (TP) underwent recolonization during the Quaternary and may have had distinct range dynamics in response to the last glacial. To further test this hypothesis and locate the possible historical dispersal routes, we selected 20 plant species from different parts of the TP and modeled their geographical distributions over four time periods using species distribution models (SDMs). Furthermore, we applied the least-cost path method together with SDMs and shared haplotypes to estimate their historical dispersal corridors. We identified three general scenarios of species distribution change during the late Quaternary: the ‘contraction-expansion’ scenario for species in the northeastern TP, the ‘expansion-contraction’ scenario for species in the southeast and the ‘stable’ scenario for widespread species. During the Quaternary, we identified that these species were likely to recolonize along the low-elevation valleys, huge mountain ranges and flat plateau platform (e.g. the Yarlung Zangbo Valley and the Himalaya). We inferred that Quaternary cyclic glaciations along with the various topographic and climatic conditions of the TP could have resulted in the diverse patterns of range shift and dispersal of Tibetan plant species. Finally, we believe that this study would provide valuable insights for the conservation of alpine species under future climate change. [ABSTRACT FROM AUTHOR]

The hydrology of the lake-rich Tibetan Plateau is important for the global climate, yet little is known about the thermal regime of Tibetan lakes due to scant data. We (i) investigated the characteristic seasonal temperature patterns and recent trends in the thermal and stratification regimes of lakes on the Tibetan Plateau and (ii) tested the performance of the one-dimensional lake parameterization scheme FLake for the Tibetan lake system. For this purpose, we combined 3 years of in situ lake temperature measurements, several decades of satellite observations, and the global reanalysis data. We chose the two largest freshwater Tibetan lakes, Ngoring and Gyaring, as study sites. The lake model FLake faithfully reproduced the specific features of the high-altitude lakes and was subsequently applied to reconstruct the vertically resolved heat transport in both lakes during the last 4 decades. The model suggested that Ngoring and Gyaring were ice-covered for about 6 months and stratified in summer for about 4 months per year with a short spring overturn and a longer autumn overturn. In summer the surface mixed boundary layer extended to 6-8m of depth and was about 20% shallower in the more turbid Gyaring. The thermal regime of the transparent Ngoring responded more strongly to atmospheric forcing than Gyaring, where the higher turbidity damped the response. According to the reanalysis data, air temperatures and humidity have increased, whereas solar radiation has decreased, since the 1970s. Surprisingly, the modeled mean lake temperatures did not change, nor did the phenology of the ice cover or stratification. Lake surface temperatures in summer increased only marginally. The reason is that the increase in air temperature was offset by the decrease in radiation, probably due to increasing humidity. This study demonstrates that air temperature trends are not directly coupled to lake temperatures and underscores the importance of shortwave radiation for the thermal regime of high-altitude lakes. [ABSTRACT FROM AUTHOR]

Land surface models (LSMs) are useful tools to estimate land evapotranspiration at a grid scale and for long-term applications. Here, the Community Land Model, version 4.0 (CLM4.0); Dynamic Land Model (DLM); and Variable Infiltration Capacity model (VIC) were driven with observation-based forcing datasets, and a multiple-LSM ensemble-averaged evapotranspiration (ET) product (LSMs-ET) was developed and its spatial-temporal variations were analyzed for the China landmass over the period 1979-2012. Evaluations against measurements from nine flux towers at site scale and surface water budget-based ET at regional scale showed that the LSMs-ET had good performance in most areas of China's landmass. The intercomparisons between the ET estimates and the independent ET products from remote sensing and upscaling methods suggested that there were fairly consistent patterns between each dataset. The LSMs-ET produced a mean annual ET of 351.24 ± 10.7 mm yr−1 over 1979-2012, and its spatial-temporal variation analyses showed that (i) there was an overall significant ET increasing trend, with a value of 0.72 mm yr−1 ( p < 0.01), and (ii) 36.01% of Chinese land had significant increasing trends, ranging from 1 to 9 mm yr−1, while only 6.41% of the area showed significant decreasing trends, ranging from −6.28 to −0.08 mm yr−1. Analyses of ET variations in each climate region clearly showed that the Tibetan Plateau areas were the main contributors to the overall increasing ET trends of China. [ABSTRACT FROM AUTHOR]

Climatic significance of ice core stable isotope record in the Himalayas and southern Tibetan Plateau (TP), where the climate is alternately influenced by Indian summer monsoon and mid-latitude westerlies, is still debated. A newly drilled Zuoqiupu ice core from a temperate maritime glacier on the southeastern TP covering 1942-2011 is investigated in terms of the relationships between δO and climate parameters. Distinct seasonal variation of δO is observed due to high precipitation amount in this area. Thus the monsoon (June to September) and non-monsoon (October to May) δO records are reconstructed, respectively. The temperature effect is identified in the annual δO record, which is predominantly contributed by temperature control on the non-monsoon precipitation δO record. Conversely, the negative correlation between annual δO record and precipitation amount over part of Northeast India is mostly contributed by the monsoon precipitation δO record. The variation of monsoon δO record is greatly impacted by the Indian summer monsoon strength, while that of non-monsoon δO record is potentially associated with the mid-latitude westerly activity. The relationship between Zuoqiupu δO record and Sea Surface Temperature (SST) is found to be inconsistent before and after the climate shift of 1976/1977. In summer monsoon season, the role of SST in the monsoon δO record is more important in eastern equatorial Pacific Ocean and tropical Indian Ocean before and after the shift, respectively. In non-monsoon season, however, the Atlantic Multidecadal Oscillation has a negative impact before but positive impact after the climate shift on the non-monsoon δO record. [ABSTRACT FROM AUTHOR]

Based on the 13-year data from the Tropical Rainfall Measuring Mission (TRMM) satellite during 2001-2013, the influencing geographical location of the Tibetan Plateau (Plateau) monsoon is determined. It is found that the domain of the Plateau monsoon is bounded by the latitude between 27° N and 37° N and the longitude between 60° E and 103° E. According to the annual relative precipitation, the Plateau monsoon can be divided into three sections: the Plateau winter monsoon (PWM) over Iran and Afghanistan, the Plateau summer monsoon (PSM) over the central Plateau, and the transiting zone of the Plateau monsoon (TPM) over the south, west, and east edges of the Plateau. In PWM and PSM, the monsoon climatology has a shorter rainy season with the mean annual rainfall of less than 800 mm. In TPM, it has a longer rainy season with the mean annual rainfall of more than 1800 mm. PWM experiences a single-peak monthly rainfall with the peak during January to March; PSM usually undergoes a multi-peak pattern with peaks in the warm season; TPM presents a double-peak pattern, with a strong peak in late spring to early summer and a secondary peak in autumn. The Plateau monsoon also characterizes an asymmetrical seasonal advance of the rain belt. In the east of the Plateau, the rain belt migrates in a south-north orientation under the impact of the tropical and subtropical systems' oscillation. In the west of the Plateau, the rain belt advances in an east-west direction, which is mainly controlled by the regional Plateau monsoon. [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, we examined the annual precipitation amounts, the seasonality over global land and their linear trends, as well as the uncertainties in two observations (precipitation reconstruction and Global Precipitation Climatology Centre), and then compared them with historical runs by multiple models. Overall, the large-scale patterns of both the climatology of the annual precipitation amount and the seasonality are consistent between the two observations. Nevertheless, some noticeable differences existed, particularly in the regions with fewer gauge observations, such as northern Africa and the Tibetan Plateau. For long-term changes, significant drying trends during 1948-2005 were observed in the tropical areas of northern Africa, accompanied by significant wetting trends in the polar region of Canada. The seasonality change during the period was dominated by a decreasing trend in precipitation, especially in the western portion of Russia. The model simulations of the Coupled Model Intercomparison Project, Phase 5 ( CMIP5) reproduced the climatological mean state of annual precipitation and its seasonality in the observations, as well as to some extent the zonal mean trends of precipitation amounts, but did not reproduce the zonal mean trends of seasonality. The two-dimensional distribution of linear trends of annual precipitation and seasonality simulated by CMIP5 models showed little consistency with their observational counterparts. One possibility for the inconsistencies was that they were largely determined by internal variations of the climate system rather than external forcings. In contrast, it might also suggest a challenge for state-of-the-art climate models to correctly simulate the spatial distribution of responses of annual precipitation amounts and seasonality to the evolution of external forcings. Our results suggest that, in addition to the precipitation amount, seasonality should be used as a metric to assess the ability of a climate model to simulate current climate conditions and project future climate change. [ABSTRACT FROM AUTHOR]

Estimating the potential of species to cope with rapid environmental climatic modifications is of vital importance for determining their future viability and conservation. The variation between existing populations along a climatic gradient may predict how a species will respond to future climate change. Stipa purpurea is a dominant grass species in the alpine steppe and meadow of the Qinghai-Tibetan Plateau (QTP). Ecological niche modelling was applied to S. purpurea, and its distribution was found to be most strongly correlated with the annual precipitation and the mean temperature of the warmest quarter. We established a north-to-south transect over 2000 km long on the QTP reflecting the gradients of temperature and precipitation, and then we estimated the morphological by sampling fruited tussocks and genetic divergence by using 11 microsatellite markers between 20 populations along the transect. Reproductive traits (the number of seeds and reproductive shoots), the reproductive-vegetative growth ratio and the length of roots in the S. purpurea populations varied significantly with climate variables. S. purpurea has high genetic diversity (He = 0.585), a large effective population size (Ne >1,000), and a considerable level of gene flow between populations. The S. purpurea populations have a mosaic genetic structure: some distant populations (over 1000 km apart) clustered genetically, whereas closer populations (< 100 km apart) had diverged significantly, suggesting local adaptation. Asymmetrical long-distance inter-population gene flow occurs along the sampling transect and might be mediated by seed dispersal via migratory herbivores, such as the chiru (Pantholops hodgsonii). These findings suggest that population performance variation and gene flow both facilitate the response of S. purpurea to climate change. [ABSTRACT FROM AUTHOR]

The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland. [ABSTRACT FROM AUTHOR]

Unrealistic topographic effects are generally incorporated in global climate simulations and may contribute significantly to model biases in the Asian monsoon region. By artificially implementing the Arakan Yoma and Annamese Cordillera-two south-north-oriented high mountain ranges on the coasts of the Indochina Peninsula-in a 1° global climate model, it is demonstrated that the proper representation of mesoscale topography over the Indochina Peninsula is crucial for realistically simulating the seasonality of the East Asian-western North Pacific (EAWNP) summer monsoon. Presence of the Arakan Yoma and Annamese Cordillera helps simulate the vertical coupling of atmospheric circulation over the mountain regions. In late May, the existence of the Arakan Yoma enhances the vertically deep southwesterly flow originating from the trough over the Bay of Bengal. The ascending southwesterly flow converges with the midlatitude jet stream downstream in the southeast of the Tibetan Plateau and transports moisture across the Indochina Peninsula to East Asia. The existence of the Annamese Cordillera helps the northward lower-tropospheric moisture transport over the South China Sea into the mei-yu-baiu system, and the leeside troughing effect of the mountains likely contributes to the enhancement of the subtropical high to the east. Moreover, the eastward propagation of wave energy from central Asia to the EAWNP suggests a dynamical connection between the midlatitude westerly perturbation and mei-yu-baiu. Including the Annamese Cordillera also strengthens a Pacific-Japan (PJ) pattern-like perturbation in late July by enhancing the cyclonic circulation (i.e., monsoon trough) in the lower-tropospheric western North Pacific. This suggests the contribution of the mountain effects to the intrinsic variability of the summer monsoon in the EAWNP. [ABSTRACT FROM AUTHOR]

The evolution of plateau monsoons is essential to synoptic climatology processes over the Qinghai-Xizang Plateau. Based on ERA-Interim Reanalysis data covering 1979-2014 from the European Centre for Medium-Range Weather Forecasts (ECMWF), we propose a new plateau monsoon index (ZPMI) that can effectively reflect the evolution of monsoons and compare this new index with the existing Plateau Monsoon Indices (PMI), i.e., the Traditional Plateau Monsoon Index (TPMI), the Dynamic Plateau Monsoon Index (DPMI), and the PMI proposed by Qi et al. (QPMI). The results show that the onset and retreat of plateau monsoons determined by the TPMI are approximately 1-2 months earlier than those of the ZPMI and DPMI and that the ZPMI can better reflect seasonal and inter-annual variations in precipitation over the plateau. The plateau summer and winter monsoons have similar inter-annual and inter-decadal variation characteristics and show a rising trend, but the increasing trend of the summer monsoon is more significant. The ZPMI is also capable of effectively reflecting meteorological elements. In stronger plateau summer monsoon years, more (less) precipitation and a higher (lower) air temperature appear over the eastern and central (western) plateau. The ZPMI and soil moisture in April and May are used to explore the influence of soil moisture on plateau monsoons, and a significant correlation is found between the plateau soil moisture in the spring (April-May) and plateau summer monsoons. It is found that when the soil moisture over the central and eastern plateau is higher (lower) than normal (while the soil moisture over the western plateau is lower (higher)), the plateau summer monsoon may be stronger (weaker). [ABSTRACT FROM AUTHOR]

Knowledge about the spatiotemporal tree growth variability and its associations with climate provides key insights into forest dynamics under future scenarios of climate change. We synthesized 17 tree-ring width chronologies from four tree species at the high-elevation sites in the southeast Tibetan Plateau (SETP) to study the regional tree growth variability and climate-growth relationships. Despite of diverse habitats and different physiological characteristics of these species, these tree-ring chronologies shared a significant common variance in SETP. An unprecedented increase in the shared variance is found along the latter half of the 20th century, coinciding with the enhancement of the frequency of extreme rings among chronologies. It is found that minimum winter temperature tends to be the dominant climate for trees in this region. The site-specific responses in cold (1965–1980) and warm (1990–2005) intervals by means of Fuzzy Cmeans (FCM) clustering reveal that the remarkable enhancement of growth synchrony among trees mainly occur in warm conditions. This is different from previous findings indicating that increased consistence among temperature sensitive tree rings in cold periods. This may be related to the reduced temperature sensitivity of regional tree growth as winter minimum temperature is lower than a certain threshold, which is in agreement with the “principle of ecological amplitude”. In addition, it is worth noting that precipitation in June have started to restrain the tree growth since the beginning of the 1980s, which is possibly an important contributor for synchronized growth among trees in SETP. [ABSTRACT FROM AUTHOR]

Glaciochemistry can provide important information about climatic change and environmental conditions, as well as for testing regional and global atmospheric trace transport models. In this study, δ18O and selected chemical constituents records in snowpits collected from eight glaciers in the Tibetan Plateau and adjacent areas have been investigated. Drawing on the integrated data, our study summarized the seasonal and spatial characteristics of snow chemistry, and their potential sources. Distinct seasonal patterns of δ18O values in snowpits indicated more negative in the south TP controlled by Indian monsoon, and less negative in the north TP and Tien Shan. Overall increasing concentrations of microparticles and crustal ions from south to north indicated a strength of dust deposition on glaciers from semi-arid and arid regions. Principal component analysis and air mass trajectories suggested that chemical constituents were mainly attributable to crustal sources as demonstrated by the high concentrations of ions occurring during the non-monsoon seasons. Nevertheless, other sources, such as anthropogenic pollution, played an important role on chemical variations of glaciers near the human activity centers. This study concluded that air mass transport from different sources played important roles on the spatial distributions and seasonality of glaciochemistry. [ABSTRACT FROM AUTHOR]

Aims: A lacking of understanding about cooling effects on methane (CH) fluxes and potential asymmetrical responses to warming and cooling causes uncertainty about climate change effects on the atmospheric CH concentration. We investigated CH fluxes in an alpine meadow on the Tibetan Plateau in response to climate warming and cooling. Methods: A 2-year reciprocal translocation experiment was implemented to simulate climate warming (i.e. downward translocation) and cooling (i.e. upward translocation) along an elevation gradient with four different vegetation types (at 3200, 3400, 3600 and 3800 m elevation) during the growing season (May to October) in 2008 and 2009. Results: Although the effects of warming and cooling varied depending on vegetation type, elevation and timescale (i.e., daily and seasonally), warming increased average seasonal CH uptake by 60 %, while cooling reduced it by 19 % across all vegetation types, based on a 1.3-5.1 °C difference in soil temperature at 20 cm depth. Soil temperature over the range of 4-10 °C explained 11-25 % of the variation in average seasonal CH fluxes, while there was no relationship with soil moisture over the range of 13-39 % and soil NH-N and NON content. Methane uptake was more sensitive to warming than to cooling. Conclusions: Because of warming and cooling spells in the alpine region, warming effects on CH uptake would be over-estimated by 64 % if cooling effects on it are not considered. Our findings suggest that asymmetrical responses of CH fluxes to warming and cooling should be taken into account when evaluating the effects of climate change on CH uptake in the alpine meadow on the Tibetan plateau. [ABSTRACT FROM AUTHOR]