The great Himalayas, the world’s highest mountain system, is home to millions of people and hundreds of unique species. It has one of the world's largest concentrations of cryospheric components (glaciers, snow, and permafrost). The Himalayas supply continued meltwater to some of Asia’s greatest river systems and play a vital role in the South Asian monsoon environment by guarding theIndian subcontinent from the dry, cold air masses of central Asia and blocking the warm, moist airflow from the Indian Ocean. Unfortunately, this water tower has been experiencing rapid changes driven by climate change in recent decades. Changes in this region have had and will continue to have major negative consequences for people living in the area and globally. However, changes in the climate extremes and their consequences have not been understood well yet because of the extreme topography that hinders the establishment and maintenance of monitoring networks. We will introduce some outstanding ongoing research activities in understanding key processes and changes in high-mountain meteorology, climate extremes, and glacier evolution over the southern slopes of the Himalayas. Results suggest that elevation-dependent warming accompanied by rapid glacier retreat is accelerating in the region. In addition, climate extremes are likely to increase with intensifying drought and floods. 

How to cite: Aryal, D., Shrestha, D., and Bagale, D.: Changing climate and its impacts over the southern slope of the Himalayas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6210, https://doi.org/10.5194/egusphere-egu23-6210, 2023.

Increased attention directed at cryosphere hydrology is prompted by climate change. In spite of an increasing number of field measurements and modeling studies, the impact of cryospheric change, especially of frozen soil, on hydrological processes at the catchment scale is still largely unclear. Traditional frozen soil hydrology models have mostly been developed based on a “bottom-up” approach, i.e. by aggregating prior knowledge at point scale, which is an approach notoriously suffering from equifinality and uncertainty. Therefore, in this study, we explore the impact of frozen soil at catchment-scale, following a “top-down” approach, implying: expert-driven data analysis -> qualitative perceptual model -> quantitative conceptual model -> testing of model realism -> future prediction. The complex mountainous Hulu catchment, northeast of the Tibet Plateau (TP), was selected as the study site. Firstly, we diagnosed the impact of frozen soil on catchment hydrology, based on multi-source field observations, model discrepancy, and our expert knowledge. Two new typical hydrograph properties were identified: the low runoff in the early thawing season (LRET) and the discontinuous baseflow recession (DBR). Secondly, we developed a perceptual frozen soil hydrological module, to describe the LRET and DBR properties. Thirdly, based on the perceptual model and a landscape-based modeling framework (FLEX-Topo), a semi-distributed conceptual cryosphere-hydrologic model (FLEX-Cryo) has been developed, considering all cryospheric factors, including glacier and snow accumulation/ablation, and soil freeze/thaw processes. The results demonstrate that the FLEX-Cryo model can represent the effect of soil freeze/thaw processes on hydrologic connectivity and groundwater discharge and significantly improve hydrograph simulation. Furthermore, its realism has been confirmed by alternative multi-source and multi-scale observations, particularly the freezing and thawing front in the soil, the lower limit of permafrost, and the trends in groundwater level variation. In the end, we used the FLEX- Cryo model to predict the impacts of future climate change on hydrology, including the glacier retreat, the decreasing snow cover area, and permafrost degradation. The FLEX- Cryo model is a novel conceptual cryosphere-hydrologic model, which represents these complex processes and has potential for wider use in the vast TP and other cold mountainous regions.

How to cite: Gao, H., Chang, Z., Han, C., Chen, R., Wang, K., Fenicia, F., and Savenije, H.: Cryospheric-hydrologic modeling and prediction of a mountainous catchment in the northeast Tibet Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4693, https://doi.org/10.5194/egusphere-egu23-4693, 2023.

Extreme cooling during boreal winter in Tibetan Plateau (TP) poses great threats to local environment and people’s live safety, and it has usually been attributed to climate internal varaibility. Here we show that the recent five large tropical volcanic eruptions since 1863  induced an extreme TP cooling up to -0.8 K in the first boreal winter post-eruptions, much larger than the global average terrestrial cooling of -0.3 K. This extreme TP cooling response (-0.79 K)  to tropical eruptions is simulated by the multimodel ensemble mean of the Phase 6 Coupled Model Intercomparison Project when realistic sea surface temperature is specified for the atmospheric models, and it is much larger than the direct aerosol cooling (-0.36 K) simulated by the historical runs. The positive North Atlantic Oscillation during the post-eruption winter plays the key role in amplifing the TP cooling through atmospheric teleconnection, which overwhelms the warming response associated the frequently occurring El Niños. Results from this study put into perspective the potential volcanic contribution in certain extreme Tibetan Plateau cooling events. 

How to cite: Liu, F. and Dong, W.: Extreme Tibetan Plateau cooling caused by tropical volcanism, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2473, https://doi.org/10.5194/egusphere-egu23-2473, 2023.

To explore the driving mechanisms of elevation-dependent warming (EDW) over the Tibetan Plateau (TP), the output from a suite of numerical regional climate models (RCMs) under the Coordinated Regional Climate Downscaling Experiments-East Asia (CORDEX-EA-II) project is examined. Results show that all RCMs can broadly capture the observed temperature distributions over the TP with consistent cold biases, and the spread in temperature simulations could to a large extent be explained by their spreads in the surface albedo feedback (SAF). The simulated EDW during winter is mainly caused by the SAF, and the clear-sky downward longwave radiation (LW) plays a secondary role in shaping EDW. Further analysis suggests that a marked EDW signal over the TP is simulated under the Representative Concentration Pathway emission scenario 8.5 (RCP8.5) for all seasons, particularly in autumn, and the SAF is also the primary contributor to EDW and acts as the main source of uncertainty in EDW projections among RCMs. The LW is the dominant factor in regulating the surface air temperature change over the TP, and its contribution to EDW is model-dependent. Furthermore, the structure and magnitude of projected EDW are sensitive to the RCM physics and driving GCM, as they can alter the projections of snow cover and albedo, which modulate the simulated SAF and its effect on EDW.

How to cite: niu, X.: Contributors to the Elevation-Dependent Warming over the Tibetan Plateau in the CORDEX-EA-II simulations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3729, https://doi.org/10.5194/egusphere-egu23-3729, 2023.

The Tibetan Plateau (TP) features unique and highly heterogeneous soils, terrains, vegetation, and climate. Accurately modeling complex freeze-thaw processes and their hydrothermal impacts remains a great challenge. This study focused on deciphering the spatiotemporal variability of diverse parameterization schemes in the soil hydrothermal simulations using the Noah-MP land surface model. We first discussed the spin-up time required by the model to reach the equilibrium state, and then performed a sensitivity analysis of these schemes. The Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature and Soil Moisture Active Passive (SMAP) remote sensing products were used as benchmarks to evaluate the schemes’ performance. Results show that longer spin-up times are required in permafrost regions owing to water phase changes. Ground temperature and soil temperature are mainly sensitive to energy-related schemes. Vegetation-related schemes play an important role after the growing season begins on the southeastern TP. Soil water content shows strong sensitivity to schemes related to both water and energy transport. However, the sensitivity of these energy-related schemes is weakened when simulating total soil moisture, including the total amount of water and ice, indicating that these schemes have marked impacts on soil freeze-thaw processes. These results reveal the different spatial (both regional and depth-related) and temporal effects of parameterization schemes; we also provided a preliminary selection of these schemes at a regional scale that could facilitate the further improvement of the soil hydrothermal simulations on the TP.

How to cite: Hu, W., Ma, W., Yang, Z.-L., and Xie, Z.: Sensitivity Analysis of the Noah-MP Land Surface Model for Soil Hydrothermal Simulations over the Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4101, https://doi.org/10.5194/egusphere-egu23-4101, 2023.

Precipitation patterns and variations over the Tibetan Plateau (TP) are mainly dominated by the Asian summer monsoon, the westerlies and their interactions. The precise scope of the Asian summer monsoon's influence, however, remains unclear. Referring to the climatological northern boundary index of the East Asian summer monsoon, this paper demonstrates that the 300 mm precipitation from May to September can be used as an index of the northern boundary of the Asian summer monsoon over the TP, and explores the spatial characteristics of the climatological and interannual northern boundary. The results show that the climatological northern boundary of Asian summer monsoon over the TP is located along the eastern Qilian Mountains-Tanggula Mountains-Qiangtang Plateau-Gangdise Mountains-Western Himalayas. It describes the boundary of the dryland during the rainy season and depicts the location of the convergence of westerly wind (westerlies) and southerly wind (monsoon) at lower troposphere over the TP. Precipitation variations in the north (south) area to the climatological northern boundary are considerably positively associated with changes in the latitudinal (longitudinal) water vapour budget. The interannual fluctuation range of northern boundary and the distribution of the TP's vegetation are related. The climatological northern boundary can more accurately reflect the region that is continuously under the influence of the monsoon and has a clearer understanding of the boundaries in the westerlies-monsoon circulation, ecology, and climate than the meteorological northern boundary (the pentad precipitation more than 4 mm/day). The westerlies influence zone, monsoon influence zone, and westerlies-monsoon transition zone are identified based on the interannual fluctuation range of northern boundary. This study can serve as a foundation for further investigation into the linkages between the westerlies-monsoon and the TP's hydrological and ecological systems. 

How to cite: Huang, L., Chen, J., and Chen, F.: The northern boundary of the Asian summer monsoon and division of westerlies and monsoon regimes over the Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15353, https://doi.org/10.5194/egusphere-egu23-15353, 2023.

Upper Indus Basin (UIB) represents three vast mountain ranges of the Himalayan-Karakoram-Hindukush (HKH) ranges in Pakistan. Recent regional warming trends even at high altitudes have confirmed the alteration of the hydrological cycle attributed to global warming. This warming tendency affects the monsoon precipitation in terms of wetting and drought in Pakistan with unprecedented intensity, causing either severe flooding or episodic drought. Therefore, it is worth observing the recent spring and summer monsoon changes in extreme precipitation and drought severity throughout Pakistan. The present study examined 8 precipitation indices in the past 50-year period (1971–2020) (stretched to two data periods) using Mann–Kendall and Sen’s method to investigate the direction and magnitude of the observed trends. For drought estimation, the Percentage Normal (PN), and Percentage Deviation (PD) indexes were analyzed. We observed that spring and summer wet days significantly increased in the central-eastern (Kakul, Kotli, Jhelum) and western (Cherat, Chitral, Peshawar) regions in the 1st data period but significantly decreased in areas including the southern region in the 2nd data period. We further observed the high-intensity precipitation days (R10, R20) in the same seasons. The intensity of summer R20 was much stronger throughout Pakistan in the 1st data period which reduced significantly during the 2nd data period in northern and southern regions. We extended the circle of investigation to very heavy and extreme precipitation (R30 and R50). The intensity of R30 and R50 in summer followed the same pattern as observed for R10 and R20. However, R30 and R50 in pre-monsoon significantly increased in the northern, east-western, and south-eastern regions during the 2nd data period. Similarly, drought analysis proposed an extreme wetting tendency in the western UIB and lower areas of southern Punjab in the last two decades. Summer monsoons and westerly humid regions also experienced severe drought in terms of heavy and very heavy precipitation extremes. Our results concluded that the most significant changes in precipitation extremes and drought severity occurred with higher intensity and recurring frequency for all indices in spring and summer monsoon during the 2nd data period.

How to cite: Ali, M. A., Latif, Y., sahar, A., and Yaseen, M.: Drought analysis under changing precipitation extremes in the Upper Indus Basin Pakistan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8639, https://doi.org/10.5194/egusphere-egu23-8639, 2023.

Global warming accelerates the water cycle worldwide, and directly affects hydrological changes and may cause changes in water availability. The Tianshan Mountains, known as “water tower of Central Asia”, is situated in the Eurasia hinterland. It serves as the main water source and ecological barrier in Central Asia. Most rives originated from the Tianshan Mountains are recharged with rainfall, glacier melt and snow meltwater. The hydrological processes in the Tianshan Mountains are strongly affected by changes in temperature and precipitation, as well as changes in the snow and glaciers. Increases in temperature have important consequences for the hydrological cycle, particularly in areas dominated by glacier and snow melt.

This study systematically investigated precipitation and temperature changes and their impacts on glaciers, snow cover and hydrological processes in the Tianshan Mountains using station observations, remote sensing data and reanalysis data. In a warming climate, precipitation is more likely to occur as rainfall rather than snowfall. Temperature-induced precipitation shifted from snow to rain since mid-1990s, with S/P experiencing an overall declining trend at a rate of 0.5%/decade. In addition, an overall increase in extreme precipitation was detected, as reflected in 25 indices. The number of consecutive dry days decreased from 87.02 to 69.35 while the number of consecutive wet days increased from 3.89 to 4.61. Changes in extreme precipitation frequency were shown to increase with event rareness. For R95p, the observed changes in frequency are 34.46%, but these jump to 96.58% for R99p.  By creating a long-term, high-quality, daily snow cover extent (HMASCE) product (1982–2019, spatial resolution of 5 km), the spatial and temporal variability in snow metrics (snow cover area and snow cover phenology) has investigated. Snow cover in the Tian Shan region showed a slight increase during this period, mainly in West Tianshan (0.66% a^-1), Hissar Alay (0.64% a^-1), and East Tianshan (0.24% a^-1).

Approximately 97.52% of glaciers in the Tianshan Mountains showed a retreating trend. For the northern TianShan Mountains,  total area and volume of glaciers exhibited negative trends, decreased by 456.43 km² (16.08%) and 26.14 km³ (16.38%), respectively, from 1990 to 2015. The reduction in the glacier area exhibited an accelerating trend, with a decreasing rate of 0.60% a^-1 before 2000, but of 0.71% a^-1 after 2000. River runoff responds in a complex way to changes in climate and cryosphere. For example, the runoffs of the Kaidu River and the Aksu River, located in the south flank of the Tianshan Mountains, have increased by 27.4% and 14.4%, respectively, during 1960 to 2021. The total water storage in the Tianshan Mountains also experienced a significant decreasing trend with a rate of 12.12 mm a^-1 during 2020~2021..

This study sheds light on current and future changes in water cycle under global warming in the Tianshan Mountains. More efforts should be made on the interpretation of impacts and mechanisms of these changes on runoff, which is a key factor that controls the amount and seasonality of freshwater resources for domestic and agricultural needs.

How to cite: Chen, Y., Fang, G., and Li, Z.: Recent climate and hydrological changes in the Tianshan Mountains, Central Asia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2478, https://doi.org/10.5194/egusphere-egu23-2478, 2023.

This research utilized GeoSOS-FLUS model to simulate and predict the distribution of vegetation coverage grade in the Tibetan Plateau in the year 2035 under two scenarios: natural development scenario based on historical evolution projection, and ecological protection scenario based on limited transformation policy. First of all, future precipitation and maximum temperature are selected as the main driving factors, supplemented by other factors including relative humidity, sunshine hours, population spatial distribution, slope, slope aspect, elevation, distance to railway and distance to highway, etc.. The vegetation coverage grade of the Tibetan Plateau in 2003 is taken as the base period, and that in 2019 is taken as the end period. Then, a GeoSOS-FLUS prediction model is constructed, based on the cost matrix and neighborhood factors and other related parameters obtained from the two scenarios. Finally, the future vegetation coverage grade distribution in 2035 is predicted by using Markov chain.

The results indicated that:

 ( 1 ) From 1998 to 2019, the bare land of the Tibetan Plateau has the tendency of been transformed into low vegetation coverage, medium vegetation coverage or medium-high vegetation coverage, whereas the area of high vegetation coverage is decreasing.

( 2 ) Under the natural development scenario, the areas of the bare land, medium-high and high vegetation coverage of the Tibetan Plateau in 2035 will be reduced by about 2 % compared with the actual vegetation coverage in 2019; the areas of low and medium vegetation coverage will be increased by 2.8 % and 10.3 % respectively. Under this scenario, the vegetation coverage evolution of the Tibetan Plateau bears a positive trend, although the trend will be weakened compared to the historical period.

( 3 ) Under the ecological protection scenario, compared with the natural development scenario, the areas of bare land and high vegetation coverage will decrease, and the area of low, medium and medium-high vegetation coverage of the Tibetan Plateau in 2035 will increase. Compared with the results predicted under the natural development scenario, under the ecological protection scenario, the improvement of future vegetation coverage of the Tibetan Plateau is very obvious, and the improvement is mainly contributed by the increase of medium vegetation coverage.

How to cite: Dong, X. and Gong, C.: Simulation of Future Vegetation Coverage Prediction under Different Development Scenarios in the Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17136, https://doi.org/10.5194/egusphere-egu23-17136, 2023.

Despite knowledge of the presence of the Tibetan Plateau (TP) in reorganizing large-scale atmospheric circulation, it remains unclear how surface albedo darkening over TP will impact local glaciers and remote Asian monsoon systems. Here, we use a coupled land-atmosphere global climate model and a glacier model to address these questions. Under a high-emission scenario, TP surface albedo darkening will increase local temperature by 0.24 K by the end of this century. This warming will strengthen the elevated heat pump of TP, increasing South Asian monsoon precipitation while exacerbating the current “South Flood-North Drought” pattern over East Asia. The albedo darkening-induced climate change also leads to an accompanying TP glacier volume loss of 6.9%, which further increases to 25.2% at the equilibrium, with a notable loss in western TP. Our findings emphasize the importance of land-surface change responses in projecting future water resource availability, with important implications for water management policies.

How to cite: Tang, S., Vlug, A., Piao, S., Li, F., Wang, T., Krinner, G., Li, L. Z. X., Wang, X., Wu, G., Li, Y., Zhang, Y., Lian, X., and Yao, T.: Regional and tele-connected impacts of the Tibetan Plateau surface darkening, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2550, https://doi.org/10.5194/egusphere-egu23-2550, 2023.

High Mountain Asia (HMA), known as Earth’s “third pole” and “Asia’s water tower,” is the largest glacier and snow reservoir on Earth except for the polar ice sheets. Snow is an important component of the HMA cryosphere, and its variability directly affects the water and energy balances in the region. Identifying long-term changes in snow cover in the HMA region is important for the development of downstream water resources, prevention of water disasters, and survival and social stability of the “Third Pole” region.

We had developed a long-term, high-quality, daily High Mountain Asia Snow Cover (HMASCE) product to systematically study the snow cover indicators (SCA and snow cover phenology (SCP)) in different sub-regions and altitudes in HMA over the past 40 years in the context of global climate change. The results show that (1) the accuracy of the HMASCE product was validated using station snow depth data, with OA, PA, and UA values of 81.99%, 84.20%, and 76.39%, respectively. (2) the SCA shows a significant trend of shrinkage (-0.56% a^-1), snow cover days (SCD) shortens by 15.5 days, and snow cover start date (SOD) is delayed by about 5.6 daysand snow cover end date (SED) has advanced by 10 d in HMA over the last 40 years. (3) Another important finding is the altitudinal dependence of SCD, where, below 5000 m, higher altitudes experience lead to greater SCD reduction than lower altitudes. The possible mechanisms underlying this phenomenon related to the region's own characteristics, the elevation dependence of warming (EDW), and the increased black carbon.

How to cite: Li, Y. and Chen, Y.: The continuing shrinkage of snow cover in High Mountain Asia over the last four decades, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16661, https://doi.org/10.5194/egusphere-egu23-16661, 2023.

Land surface temperature (LST) is an important parameter in land surface processes. Improving the accuracy of LST retrieval over the entire Tibetan Plateau (TP) using satellite images with high spatial resolution is an important and essential issue for studies of climate change on the TP. In this study, a random forest regression (RFR) model based on different land cover types and an improved generalized single-channel (SC) algorithm based on linear regression (LR) were proposed. Plateau-scale LST products with a 30 m spatial resolution from 2006 to 2017 were derived by 109,978 Landsat 7 Enhanced Thematic Mapper Plus images and the application of the Google Earth Engine. Validation between LST results obtained from different algorithms and in situ measurements from the Tibetan observation and research platform showed that the root mean square errors of the LST results retrieved by the RFR and LR models were 1.890 K and 2.767 K, respectively, which were smaller than those of the MODIS product (3.625 K) and the original SC method (5.836 K).

How to cite: Wang, X., Zhong, L., and Ma, Y.: Estimation of 30 m land surface temperatures over the entire Tibetan Plateau based on Landsat-7 ETM+ data and machine learning methods, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6093, https://doi.org/10.5194/egusphere-egu23-6093, 2023.

The Tibetan Plateau is one of the most sensitive areas responding to global environmental changes, especially global climate change, and has thus been deemed an important indicator of global change. The vegetated areas in Tibetan Plateau are expected to respond to environmental change because vegetation cover is a key part of the ecosystem. However, the vegetation disturbance behavior in the region remains poorly understood. Since the various change detection algorithms perform differently across complex natural systems, the combination of different approaches is currently a mainstream solution for better quantification of vegetation disturbances. The main objective of this study was to map the vegetation disturbances across the Tibetan Plateau using satellite data and a combination of change detection algorithms. We applied an ensemble strategy and satellite data to map the three decades of vegetation disturbances over the Tibetan Plateau. The two leading disturbance detection algorithms (Continuous Change Detection and Classification algorithm, CCDC; Landsat-based detection of Trends in Disturbance and Recovery algorithm, LandTrendr) were involved in the ensemble strategy with a Random Forests-based fusion for aggregating the classifiers. The reference data were taken from a total of 15,680 manually interpreted Landsat pixels, including 1,739 disturbed vegetation points, 3,696 stable vegetation points, and 10,245 non-vegetation points. It is found that a total area of about 105.83 M ha has experienced vegetation disturbance with considerable spatial variability across the Tibetan Plateau over the past three decades, and large differences among the disturbance patches were found. The identified unexpected scale of vegetation disturbance can further facilitate the understanding of the dramatic ecological changes in the ecologically fragile Tibetan Plateau region in response to climate change and more frequent human activities.

How to cite: Wang, Y., Guo, H., Xu, X., He, Y., and Shi, Z.: Mapping the vegetation disturbances over the Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16770, https://doi.org/10.5194/egusphere-egu23-16770, 2023.

The Tibetan Plateau snow cover is characterized by rapid changes on a weekly time-scale, which can cause rapid changes in surface albedo. Using snow and surface albedo data from satellite observations, we find that changes in snow coverage on the Tibetan Plateau dominate the rapid changes in surface albedo. However, snow depth also has a distinct effect on rapid changes in surface albedo in some areas especially with unstable snow cover. We test the snow depth-dependent snow albedo parameterization scheme in the land surface model. The results show that whether or not the variation of snow albedo with snow depth is considered directly affects the rapidly changing characteristics of the simulated snow cover on the Tibetan Plateau, which further affects the simulation of surface albedo. These results highlight the rapid response of surface albedo to both snow coverage and depth over the Tibetan Plateau.

How to cite: Miao, X., Guo, W., Li, W., and Cao, Y.: Tibetan Plateau surface albedo responds instantly to both snow coverage and depth, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3907, https://doi.org/10.5194/egusphere-egu23-3907, 2023.

Accurate assessment of the state and changes of permafrost active layer thickness (ALT) on the Qinghai-Tibet Plateau (QTP) is critical to understanding the underlying processes driven by the global climate change. The Interferometric Synthetic Aperture Radar (InSAR) technology has been proven to be a method for quantifying deformation caused by natural and degradational processes of permafrost changes. Given its high accuracy, this method has been applied to monitoring local and regional permafrost deformation in QTP. However, there is a lack of improved large-scale regional ALT mapping algorithm using the accurate InSAR deformation data. Here, we examine the complex processes where the active layer melts spatio-temporally in depth during the thawing season, and the ground subsides due to the volume difference induced by the ice - water conversion. We developed a new model that infers ALT from the surface subsidence with help of other parameters in the process. This model takes the advantage of long-term InSAR derived deformation data, including both seasonal signal and inter-annual trend. In addition, it introduces an empirical parameter to represent the contribution of the ice-water phase change with consideration of additional water contribution from other sources. We implemented the developed method in Kekexili regional of the QTP. The seasonal deformation was obtained from radar images of Sentinel-1 by using the Small Baseline Subset Interferometry (SBAS-InSAR) technology. The thawing water was estimated in combination with soil moisture, precipitation, evapotranspiration and runoff data. Based on deformation data, vegetation cover information and existing ALT products, the empirical parameter was obtained by a data-driven regression method. Finally, a new InSAR-derived permafrost ALT map in the Kekexili region from 2015 to 2020 is produced. The results show that the average ALT is of 1.94 m with a standard deviation of 0.35 m. A comparative discussion with permafrost maps produced using other methods is given.

How to cite: Li, R., Chang, T., Han, J., Yi, Y., Hao, T., Lu, P., Wen, Y., and Li, Z.: Regional map of InSAR-based active layer thickness of permafrost in Qinghai-Tibet Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10773, https://doi.org/10.5194/egusphere-egu23-10773, 2023.

In the context of global warming, the Tibetan Plateau, as the “third pole”, is still unclear about the impact of climate warming on the climate anomalies in the surrounding areas. Using mathematical statistics and climate diagnosis, we compared the anomalies of thermal and dynamic field caused by plateau warming during winter-spring with the continuous drought events in Southwest China from 1991 to 2020. Here we show that, there is a three-year lagged correlation between the plateau climate warming and southwest China precipitation. The correlation coefficient between sensible heat and drought degree exceeds -0.498 and confidence level is greater than the 95%. The warming of the Tibetan Plateau leads to the positive vorticity change around the plateau, which strengthens the westerly circulation of the southern branch, weakens the westerly (cold) wind of the northern branch. Thus, the Southwest China is controlled by a single dry and warm air mass,  and eventually leads to continual winter-spring drought events. When the plateau warming is accompanied by the La Niña event, the drought will last longer and be stronger. The results are of  reference value for the prediction of extreme climate under the action of special terrain, and have certain significance for local disaster prevention.

How to cite: Shi, H., Tian, R., Lou, X., and Jin, Z.: Warming of Tibetan Plateau and continual winter-spring drought in Southwest China in the background of global warming, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4641, https://doi.org/10.5194/egusphere-egu23-4641, 2023.

The Yarlung Tsangbo Grand Canyon (YGC), one of the world’s deepest canyons, is located within the East Himalayas, which are remote and poorly instrumented. A rain‐gauge network was established around the YGC region. More than three years data collected from the network, disclose that the spatial pattern of rainfall distribution. There are two regions (500 m and 2500 m AMSL) with high precipitation in the YGC. Diurnal cycles showed some variations among sites, but a clear floor was visible around afternoon and peak values exhibited in the early morning. The monthly precipitation in the YGC region shows two peaks in April and July. Vertical convection and vapor transport are important for extreme rainfall in this region.

GPM IMERG evaluation demonstrates that the data reasonably captured the observed seasonal and diurnal variations in the precipitation but with much weaker seasonal and diurnal variations compared with the gauge data. The GPM IMERG overestimated and underestimated the light and heavy precipitation, respectively, leading to a significant underestimation of the rainfall frequency and intensity at both the daily and monthly scales. Some possible mechanism for the underestimation was investigated to help scientists to improve the satellite precipitation product.

Our observations indicate that ERA5 cannot reproduce the diurnal patterns of precipitation in the YGC region. ERA5 showed a wet bias when estimating light cumulus rainfall and a dry bias when estimating heavier (convective) precipitation. The erroneous diurnal variation of ERA5 precipitation (false afternoon rainfall) was due to the CAPE (Convectively Available Potential Energy)-based convective precipitation scheme. The higher ERA5 precipitation than observation was due to the large-scale rainfall scheme in the Integrated Forecasting System (IFS) of ERA5.

These analysis have help us understanding the impacts of YGC valley on the water vapor transport and extreme rainfall outbreak mechanism.

How to cite: Chen, X.: An observational view of rainfall characteristics and evaluation of rainfall products in the Yarlung Tsangbo Grand Canyon, China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2196, https://doi.org/10.5194/egusphere-egu23-2196, 2023.

Mount Emei is located in the eastern edge of the Tibetan Plateau, on the transition zone between the main body of the Tibetan Plateau and the Sichuan Basin in China. It is not only the necessary place for the eastward movement of the plateau system, but also the place where the southwest vortex begins to develop. Its special geographical location makes it particularly important to understand the turbulence characteristics and surface energy balance of this place. Based on the Platenay Boundary Layer (PBL) tower data, radiation observation data and surface flux data of Emeishan station on the eastern edge of Tibetan Plateau from December 2019 to February 2022, the components of surface equilibrium are estimated by eddy correlation method and Thermal Diffusion Equation and Correction (TDEC) method, the characteristics of surface energy exchange in Emeishan area are analyzed, and the aerodynamic and thermodynamic parameters are estimated. The results show that the annual average value of zero-plane displacement d is 10.45 m, the annual average values of aerodynamic roughness Z_0m and aerothermal roughness Z_0h are 1.65 m and 9.95 m, respectively, and the annual average values of momentum flux transport coefficient C_D and sensible heat flux transport coefficient C_H are 1.58×10^-2 and 3.79×10^-3, respectively. Under the unstable stratification, the dimensionless three-dimensional wind fluctuation variance in Emeishan area can better conform to the 1/3 power law of Monin-Obukhov similarity theory. In the near neutral case, the dimensionless velocity variances in the u, v and w directions are 2.412, 2.181 and 1.125 respectively, and the dimensionless velocity variances in the horizontal direction are greater than those in the vertical direction. The diurnal and seasonal variations of each component of surface balance are more obvious. The dominant position of sensible heat flux and latent heat flux during the day varies with seasons. The latent heat flux is dominant in summer and the sensible heat transport is dominant in winter. The diurnal variation range of surface albedo in Emeishan area shows the characteristics of large in the morning and small in the afternoon, which is an asymmetric "U" shape. Its value is between 0.04-0.08. The surface albedo in summer and autumn is higher than that in Emeishan. The influence of underlying surface on surface reflectance is much greater than other factors such as altitude, longitude and latitude.

How to cite: Li, M., Chang, N., and Ma, Y.: Study on surface layer turbulent and energy exchange in Eastern edge of the Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2539, https://doi.org/10.5194/egusphere-egu23-2539, 2023.

The remote sensing products showed significant vegetation greening during 1980-2010 under the “warm-humid” climate changes over the Tibetan Plateau. Several previous studies showed such significant increasing of vegetation NDVI  and LAI resulted an overall cooling effects on climate over the Tibetan Plateau. Our field survey in 2008 and 2018 at 36 alpine grassland sites showed that aboveground biomass increased for legumes and forbs, but decreased for grasses and sedges, resulting in no overall change in the aboveground biomass during the 10-year period. Such hiatus of Tibetan Plateau vegetation greening was also found in three remote sensing products (GLASS, Globmap, GIMMS). We run WRF4.0 model to quantify the recent vegetation impact on climate during 2008-2018 and found the recent hiatus of Tibetan Plateau vegetation greening mainly showed warming effects due to the increasing of the daily minimum air temperature. Such warming effects also increased of the active layer depth and annual thawed fraction over the seasonal permafrost regions. Although the latent heat flux was also increased, the increasing water vapor showed insignificant impact on precipitation except on the cumulus precipitation in Fall.

How to cite: Lu, Y., Yang, Y., Wang, L., and Liu, J.: Recent hiatus of Tibetan Plateau vegetation greening and the consequence impact on climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4601, https://doi.org/10.5194/egusphere-egu23-4601, 2023.

Due to the characteristics of persistence, bioaccumulation, potential for long-range environmental transport and adverse effects, the emissions and pollution characteristics of long-chain, short-chain and ultra-short-chain polyfluoroalkyl and polyfluoroalkyl substances (PFASs) are affected by International attention, especially in the Arctic, Antarctic and the third pole Qinghai-Tibet Plateau region. The Tibetan Plateau is the highest plateau in the world (averaging over 4,000 metres) and has the largest ice reserves (approximately 7,481 cubic kilometres) except for the polar regions, and is known as the water tower of Asia. Kwok et al. (2013) found that glaciers can act as temporary reservoirs for PFASs, which are released by melting glaciers under the influence of global warming. Chen et al. (2019) found that melting glaciers have become the second major source of PFASs in Lake Nam Co. Since the 1980s, global warming has led to the retreat of more than 80% of the glaciers and the expansion of more than 50% of the lakes on the Tibetan Plateau, which may intensify the release of PFASs from the glaciers. In this study, 17 water samples, 12 sediment samples and 12 soil samples were collected in the east, south, west or north direction, or in the center of Lake Nam Co in August 2020. Moreover, 23 water samples were collected from glaciers and non-glacial runoff around the lake that flow into Lake Namco. 19 PFASs (C2-C18), and their nine isomers and one main precursor FHxSA were analyzed by solid-phase extraction (two-fraction elution) and ultra-high performance liquid chromatography/tandem mass spectrometry. The results showed the concentrations of PFASs in water bodies such as lake water, glacial runoff and non-glacial runoff were the highest, with average concentrations of 3603 pg/L, 9,823 pg/L and 4,089 pg/L, respectively, which were 4 times, 7.4 and 5.6 times those of 2017. The concentrations of PFASs in soil and sediment were significantly lower than those in water bodies, 1.86 and 0.616 ng/g (dry weight), respectively. It was estimated that the PFASs input flux of surface runoff to lake reached 18,926.5mg/d, of which the glacial runoff reached 11,326.2mg/d (7.7 times that of 2017). It is very likely that the melting of glaciers accelerated the release of PFASs from glacier runoff into the water of Lake Nam Co. For all the three media, the linear chain was the most important isomer of PFOA and PFOS, and the order of the proportion of branched chain isomers was consistent (iso->5m->4m->3m-PFOS/PFOA). The PFBA concentrations were highest in lakes and surface runoff, accounting for 55.2% and 81.2% of total PFASs, respectively. PFBA and other PFASs in lake water were poorly correlated, and Cai et al. (2012) found similar results in polar glaciers, suggesting that the PFBA in the Lake Nam Co probably mainly came from the melting of glaciers. In the future, global warming may further accelerate the melting of glaciers and the release of PFASs in glaciers, and the changing trend of PFASs concentrations in water bodies on the Tibetan Plateau should be continuously tracked.

How to cite: Peng, L., Wu, J., Dong, B., Zhuang, Y., Wang, F., Yang, L., Yan, Y., Li, J., Xie, K., Zhang, D., Liu, Z., and Duan, X.: Accelerated release of PFASs from glacier melting on the Qinghai-Tibet Plateau caused by global warming, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5857, https://doi.org/10.5194/egusphere-egu23-5857, 2023.

The spatial and temporal distribution characteristics and changes of summer precipitation over the  Tibetan Plateau(TP) is quite complicated, so it is an urgent problem to simulate the precipitation over the plateau accurately. Due to the improved resolution, dynamical downscaling modelling(DDM) at kilometer scale has shown certain value-added effects in the simulation of water vapor transport and the triggering of convection over the Tibetan Plateau, but it may still not be sufficient to simulate the precipitation characteristics of mountain observations. In this study, a DDM at 4 km resolution and a DDM at 28 km resolution were conducted in summer (June 1 to August 31, 2014). Based on the station observation datasets, the hourly precipitation changes of ERA5 reanalysis data and the above simulation results with different resolutions were evaluated. It indicates that CPM has a significant advantage in simulating precipitation in daytime precipitation simulation, but it underestimates the precipitation at night obviously, while the performance of ERA5 and DDM show acceptable performance.Meanwhile, this situation varies greatly among different basins on TP, which is worth further analysis. The key of this study is to to fully consider small-scale physical processes and the turbulence problems involved in boundary layer processes on the basis of 4km resolution simulation, so as to explore the optimal resolution of hourly precipitation simulation over TP. The physical mechanism behind this is related to the different feedback of scale interactions caused by different resolutions, which may involve the different characterization of terrain and underlying surface features.

How to cite: Jiang, H. and Gao, Y.: Simulation of Hourly Precipitation over the Tibetan Plateau by Regional Climate Dynamical Downscaling Simulations with Different Resolutions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6694, https://doi.org/10.5194/egusphere-egu23-6694, 2023.

Through land-atmosphere interaction, the Tibetan Plateau (TP) directly or indirectly affect the weather and climate globally, nevertheless the majority regions of China. To investigate the influence of the terrestrial evapotranspiration over the TP on precipitation over its own and downstream, the water vapor tracer (WAT) method coupled with the Weather Research and Forecasting (WRF) are used in this study. According to the landing location of precipitation, the termination of the evaporative moisture over the TP could be apart into inside or outside the TP. The process in the former was named as recycling precipitation and the other was named as moving-out precipitation. The recycling precipitation was found dominate the termination of the ET, which showed a decrease gradient from eastern to western TP. The moving-out precipitation mainly spreads to the east with a few to the south. Seasonal variations suggested that more recycling precipitation occurs in summer and winter, and more the moving-out precipitation occurs in spring and autumn. The trade-off between convection and advection results in different reaches of moving-out precipitation in two seasons: the strong convection and diabatic heating plus a relative weak large-scale advection result in short reaches outside the TP in summer, while relative weak convection and strong advection result in far-reaches in autumn. This study is beneficial for the understanding of the water cycle over the TP as well as the TP direct impacts mechanism on the precipitation in central and eastern China.

How to cite: Tang, Y., Dan, J., Zhang, M., Jiang, H., and Gao, Y.: How Does the Evapotranspiration Over the Tibetan Plateau Affect the Precipitation in Itself and Low Reaches?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5897, https://doi.org/10.5194/egusphere-egu23-5897, 2023.

Lake water temperature and the related thermal structure influence not only the provision of ecosystem services in lacustrine environments but also the interactions with regional climate. However, continuous lake temperature monitoring across the Tibetan Plateau is sparse, limiting our understanding of lake thermal and mixing dynamics and hindering the verification of modeling results in this region. Based on in-situ water temperature and meteorological observations, this study revealed a special summer destratification phenomenon of a deep alpine lake on the Tibetan Plateau, Langa Co. The results indicate that Langa Co is a discontinuous cold polymictic lake, which becomes completely mixed and reaches a homogeneous water temperature frequently during spring and autumn. Further, the intermittent periods of stratification in summer only last a few days, which is rare for such a deep lake (mean depth = 22 m; maximum depth = 49 m). As an example of a discontinuous cold polymictic lake that contrasts with the typical dimictic pattern of alpine lakes, studies of Langa Co help to gain insights into lake thermal processes and thermoregulation mechanisms and establish a reference for lake model evaluation and parameterization on the Tibetan Plateau.

How to cite: Su, R., Ma, W., Xie, Z., Wang, B., Hu, W., and Su, Z.: Summer Lake Destratification Phenomenon: A Peculiar Deep Lake on the Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5043, https://doi.org/10.5194/egusphere-egu23-5043, 2023.

Saline lakes play an important role in the global carbon cycle by burying carbon in sediments and emitting CO₂ to the atmosphere. A series of recent studies have found that Saline lakes of the Tibetan Plateau (TP) have a strong carbon sink function, which exhibits very different characteristics from lakes in other regions of the world.

A period of five-year data recorded by the eddy covariance (EC) systems built at Lake Nam-Co (“large lake”, area: more than 2000 km²), Lake small Nam-Co (“small lake”, area: 1.4 km²) and Nam-Co land site (“land station”, plateau meadow) have been used to study on net ecosystem exchange (NEE) characteristics over the different underlying surfaces at Lake Nam-Co Basin. The results revealed that significant differences exist in their carbon exchange processes at diurnal and seasonal variations. (1) CO₂  uptake in “large lake” occurs mainly during the freeze period, and the NEE uptake at the “land station” appears mainly in spring and summer, while “small lake” has no significant CO₂ uptake during the winter ice covered season。(2) “Large lake” has significant intra-day variation during the ice-forming season; the “land station” has close to zero values in winter but shows significant intra-day variation in spring and summer for the NEE exchange, while the “small lake” shows significant differences for wind direction from the water and from the surrounding land. Under global climate change, the lakes over the TP have expanded a large proportion right now and will continue to enlarge in the future. Our study revealed that there are significant differences in the functions of CO₂ source/sink between lakes and land, and even in different sizes of lakes on the TP. This will provide an important reference for the prediction and estimation of the carbon function changes of lakes on the TP.

How to cite: Li, W. and Wang, B.: Analysis of the diurnal and seasonal variations of NEE exchange over a large lake, a small lake and meadow surface of Lake Nam Co basin, Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4026, https://doi.org/10.5194/egusphere-egu23-4026, 2023.

This study examines the seasonal and diurnal variations of carbon dioxide and energy fluxes over three land cover types of Nepal by using the eddy covariance method from March to November 2016. The surface energy balance closures were moderate with values of about 56%, 61%, and 64% closure at Kirtipur, Simara, and Tarahara sites respectively. The monthly average values of net radiation flux and latent heat flux peaked in August at Kirtipur and Tarahara sites where as in June at the Simara site respectively. The maximum monthly average measured sensible heat flux was 37 W m−2, 43.6 W m−2, and 36.3 W m−2 in April for all the sites whereas soil heat flux was 5.1 W m−2 and 2.9 W m−2 in April for Kirtipur and Simara sites and 6.2 W m−2 in June for the Tarahara site. The magnitude of the diurnal peak of net ecosystem CO2 exchange (NEE) reached up to 11.04 μmol m−2 s−1 atKirtipur, 15.04 μmol m−2 s−1 at Simara, and 10.44 μmol m−2 s−1 at Tarahara sites respectively. Among the three study sites, the ecosystem at the Kirtipur site was a good carbon source; the ecosystems at Simara and Tarahara sites were low and had good carbon sinks in the growing season. In addition, all three different land cover ecosystem were carbon sources when accounted for during the measurement period.

How to cite: Joshi, B. B., Ma, Y., and Wang, B.: Seasonal and diurnal variations of carbon dioxide and energy fluxes over three land cover types of Nepal, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1674, https://doi.org/10.5194/egusphere-egu23-1674, 2023.