The Tibetan Plateau, also known as the world’s Third Pole, holds immense significance in the global context, influencing climate patterns, water resources, and biodiversity across Asia and even the globe. Scientific data related to the Tibetan Plateau is crucial for understanding of the complex interactions among its lithosphere, hydrosphere, cryosphere, biosphere, atmosphere, and anthroposphere. Additionally, sharing scientific data facilitates collaborative research efforts, fostering a comprehensive approach to addressing challenges such as water resource management, natural disasters, and the sustainable development of the Tibetan Plateau. By promoting and sharing scientific data of the Third Pole, the international scientific community can contribute to the understand and preservation of this vital region and its far-reaching implications for the Earth system.

The National Tibetan Plateau/Third Pole Environment Data Center (TPDC, https://data.tpdc.ac.cn) is one of the first 20 national data centers endorsed by the Ministry of Science and Technology of China in 2019. The TPDC is dedicated to consolidating and integrating extensive data resources of the Tibetan Plateau. The data center is featured by the most complete scientific data for the Tibetan Plateau and its surrounding regions, and is hosting more than 6,300 datasets collected from diverse disciplines, covering terrestrial surface, human-nature relationship, atmosphere, solid Earth, cryosphere, remote sensing, paleoenvironment, and others. The TPDC provides a cloud-based platform with integrated online data acquisition, quality control, analysis, and visualization capability to maximize the efficiency of data sharing. These advancements will also promote modeling of the dynamics in environment, ecosystem, human society, and the Earth system cross the Third Pole region, providing key data and knowledge supports to decision-making related to the region’s sustainable development.

TPDC complies with the “findable, accessible, interoperable, and reusable (FAIR)” data sharing principles and strengthens its cooperation with international organizations, such as collaborating with WOM to promote the Global Cryosphere Watch project. It also collaborates with the ICIMOD on data exchanging, observation capability, capacity-building, and joint research. As a recommended data repository for international journals like Nature, AGU, ESSD, and Elsevier to encourage data authors to share their data along publications. Additionally, the TPDC provides data support for various international science programs, including TPE, GEWEX/GASS LS4P and WCRP-CORDEX CPTP.

How to cite: Li, X., Pan, X., and Feng, M.: Promote scientific data sharing for the world’s Third Pole, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21015, https://doi.org/10.5194/egusphere-egu24-21015, 2024.

Uncontrolled human activities during the past few decades, specifically the burning of fossil fuels that release greenhouse gases have resulted in global warming and climate change. Climate change affects everyone and every region around the globe,but mountainous areas are particularly vulnerable because of their fragile topography, unique climate-sensitive ecosystems and dependency of billions of population on mountain resources. Due to the unique setup of the environment, warming in the mountainous areas, specifically the Himalayan region is expected more rapidly than the global average. Situating at the central part of the world’s largest and most complex mountain ranges, the Nepal Himalayas is not an exception;instead,the region is considered a climate change hotspot. The consequences of climate change around this region mainly include rapidly melting glaciers, formation and rapid expansion of glacier lakes, erratic rainfall, increasedfrequency and magnitude of extreme weather events, change in monsoon pattern, etc.

The historical data shows increasing precipitation in the monsoon season while precipitation is declining in dry seasons including winter. The downscaled and bias-corrected CMIP6 also consistently projects a similar pattern of precipitation in Nepal. The increasing precipitation in summer monsoon, particularly high-intensity events will bring more floods and landslides while the decreasing precipitation in dry seasons will create drought and forest fires over the region. We will present the different climate extreme indices to evaluate the impact of future climate for the Himalayan region.

How to cite: Aryal, D. and Pokharel, B.: Historical trend and future projection of climate extremes over the southern slope of Himalayas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9265, https://doi.org/10.5194/egusphere-egu24-9265, 2024.

Permafrost, a crucial component of the cryosphere, is mainly distributed in the high latitude and high altitude regions of the northern hemisphere, and is extremely sensitive to climate change. With global warming, permafrost is undergoing significant degradation worldwide, leading to substantial impacts on regional hydrological cycles, carbon cycles, ecological environments, and engineering construction. In our study, the Stefan’s solution and downscaled Coupled Model Intercomparison Project Phase 6 (CMIP6) datasets are employed to simulate the soil freeze depth, and the frost number model is utilized to calculate the frost number (F) based on the air freezing/thawing index derived from the downscaled CMIP6 datasets. A novel method was introduced to determine the optimal frost number threshold (F_t) to simulate the distribution of permafrost. The simulated permafrost distribution maps are compared with the existing permafrost distribution map to identify the optimal F_t with the Kappa coefficient as a measure of classification accuracy. Taking the Tibetan Plateau (TP) as a case study, the depth and distribution of permafrost were simulated under different Shared Socio-economic Pathways (SSP) scenarios on the TP. The changes in permafrost depth and distribution on the TP under different climate change scenarios and their impacts on eco-hydrological processes were analyzed. It is projected that the depth and area of permafrost will significantly decrease. Especially under the SSP585 scenario, by the end of the 21^st century, the permafrost of the TP will be almost completely degraded, and the regional mean SFD of the TP is projected to decrease by more than 50 cm compared to the current depth. The rapid decrease in the depth and area of permafrost on the TP may lead to a decrease in soil moisture and have adverse impacts on vegetation growth. This study provides valuable insights for understanding the changes in permafrost and their impacts on eco-hydrological processes.

How to cite: Pan, X., Li, H., and Nie, X.: Changes in Permafrost under Climate Change and Their Impacts on Eco-hydrological Processes: A Case Study of the Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21013, https://doi.org/10.5194/egusphere-egu24-21013, 2024.

Central Asia is facing a water shortage due to the negative impacts of climate change. Water resources in this region originate mainly in the mountains of Pamir and Tian-Shan due to snow-and glacier melt. Thus, it is important to understand variations in the cryosphere (snow and glaciers) in this region to foster climate change adaptation measures.This study focuses on the analysis of spatio-temporal changes of snow and glaciers in the Amu Darya, Syr Darya and Zerafshan river basins in Central Asia. Due to limited availability of observational network in the region, we used, besides available station data, also remote sensing-based snow cover area data for the period of 2000-2023. As for the glacier change analysis, we used a degree-day modelling approach to assess changes of glacier thickness in the period of 2000-2023. Eight glaciers were chosen for modelling purposes that are all located in the selected eight river basins for this study. Spatio-temporal analysis of snow cover area change show significantly decreasing number of snow cover days above a certain elevation in Upper Amu Darya and Upper Syr Darya river basins. In both river basins, there are regions with up to 40 days less snow coverage between 2000 and 2023. In the Upper Syr Darya river basins this change is observed in the Akshiirak Massif area, whereas in the Amu Darya River Basin, this change is observed in the Murghab area in the far western part of the river basin. Below a certain elevation zone, there are also areas with increased number of snow cover days of up to 10 days. The attribution of this change into meteorological parameters leads to various hypothesis. The modelling results of glacier thickness change was validated against glacier area evolution that was derived using the Landsat images.  In most of the river basins, a maximum of 60-70 meters of ice thickness loss was estimated with an increase of ice thickness of some glaciers in the accumulation area of about 10-15 meters. However, in two of the valley glaciers (Vanch and Zerafshan River Basins), higher amount of glacier thickness loss was estimated in the last 23 years.The study suggests quantified cryosphere changes in the last 23 years for Central Asian region and emphasizes the need for climate change adaptation as the water resources originating in the mountains of the region (water towers) are important for socio-economic stability.

How to cite: Gafurov, A., Busch, F., Mamaraimov, A., Gafurov, A., and Georgi, A.: Spatio-temporal cryosphere variations in the headwater river basins of Central Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18647, https://doi.org/10.5194/egusphere-egu24-18647, 2024.

Lake breezes are verified to play an important role in atmospheric boundary-layer development, convection triggering, and the transition from shallow to deep convection. The Tibetan Plateau (TP), known as the “Asian water tower”, contains more than 50% of China’s lakes in terms of area. In his study, we investigated the convection development in summer afternoons over lakeside land on the TP, the interaction between lake breezes and shallow convection triggering, the effect of lake diameter on the transition from shallow to deep convection, and the mechanism of soil moisture changes in lakeside land affecting the convection development. Using the WRF-LES model, which couples the lake model and land surface model in an idealized configuration, we performed two sets of idealized simulations with varying lake diameter and soil moisture content in the WRF-LES and found that: 1) larger lakes produce stronger lake breeze circulations and more moisture is advected from the lake to the lakeside land and lifted, creating wetter and boarder shallow convective clouds which accelerating the transition to deep convection; 2) The dryer soil induces stronger lake breeze circulations, which is beneficial for lifting the air parcels and generating moisture advection to maintain shallow convection over the lakeside land; 3) However, shallow convective clouds cannot be moistened and widened and develop into deep convection without sufficient evaporation from the ground surface in dry soil moisture conditions. Our simulation results highlight the importance of the horizontal and vertical transport of moisture by the lake breeze circulations in moistening and broadening shallow convective clouds and developing into deep convections.

How to cite: Han, C., Zhang, Y., and Ma, Y.: How lake breezes impact convection on the Tibetan Plateau: A large-eddy simulation study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7167, https://doi.org/10.5194/egusphere-egu24-7167, 2024.

The climate model provides simulation results in studying the climate change and its consequences. However, its application in a specific relatively small area (compared to global scale) is somehow confined for its lackness in high resolution and poverty in accuracy. Therefore, downscaling and bias correction are necessary to be undertaken to improve the output data from the climate model. Because a single EOF model is difficult to identify the time series change trend, this paper uses EOF and ensemble empirical mode decomposition (EEMD) coupling to accurately identify the statistical characteristics of time series to extract the temporal and spatial variation characteristics of meteorological data. In this study, the monthly mean temperature observation data set of ERA5 from 1970 to 2014 was used. First of all, six climate models and Multi-Model Ensemble (MME) average models of CMIP6 were evaluated and optimized by Taylor diagram, Taylor index, interannual variability assessment index and rank scoring method, and the best data set were chosen for the later treatment. Then, the Delta bias correction method and Normal distribution matching method were used to correct the chosen data. Finally, the temporal and spatial variation characteristics of temperature in the Tibet Plateau from 2015 to 2100 under SSP1-2.6, SSP2-4.5 and SSP5-8.5 scenarios were analyzed. The results show that: (1) Among the six CMIP6 models and MME average models selected in this paper, the EC-Earth3 model has the best performance in simulating temperature. (2) Comparing the results of the EC-Earth3 model after the Delta bias correction with the observation results, the regional averages of the deterministic coefficient (R²) and the Nash efficiency coefficient (NSE) are 0.992 and 0.983, respectively. After the Normal distribution matching method is used to correct, the regional averages of the deterministic coefficient (R²) and the Nash efficiency coefficient (NSE) are 0.990 and 0.978, respectively. Therefore, the Delta bias correction has a better correction effect on the monthly temperature of the model. (3) By coupling the EOF-EEMD method, it is found that the first typical field shows consistent changes in the whole region under the three scenarios, and there are common temperature change sensitive areas and non-sensitive areas under the SSP1-2.6 and SSP2-4.5 scenarios, namely, the northern Tibetan Plateau and the Pamir Plateau. The temperature of the second typical field shows a distribution that gradually decreases (SSP1-2.6, SSP2-4.5) or increases (SSP5-8.5) from the upper reaches of the Zhaqu River to the surrounding areas. Under the SSP1-2.6 scenario, the plateau as a whole is cooling down in the east and warming up in the west. Under the SSP2-4.5 and SSP5-8.5 scenarios, the plateau first warms up in the east and cools down in the west, and then cools down in the east and warms up in the west. This study can provide a reference bias correction method for a more accurate application of climate model data in the Tibet Plateau, and provide key basic information supporting in-depth assessment of the impact of temperature changes on water resources, ecosystems and environment in the Tibet Plateau.

How to cite: Dong, X., Zhang, X., Ma, Y., Gong, C., Hu, X., Chen, L., and Su, Z.: Identification of the characteristics of non-stationary spatio-temporal variations of future temperature in the Tibetan Plateau based on a coupled EOF-EEMD method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21227, https://doi.org/10.5194/egusphere-egu24-21227, 2024.

Understanding the seasonality of vegetation growth is important for maintaining sustainable development of grassland livestock systems over the Tibetan Plateau (TP). In this study, we investigate the shifts of the date of peak vegetation growth and its climatic controls for the alpine grasslands over the TP during 2001–2020. The date of peak vegetation growth over the TP advanced by 0.81 days decade^-1 during 2001–2020. This spring-ward shift mainly occurs in the semi-humid eastern TP, where the peak growth date tracks the advancing peak precipitation, and shifts towards the timing of peak temperature. Through analyzing the synchrony of peak vegetation growth and climatic peaks, we showed that 26% of the semi-humid eastern plateau is shifting from thermal-constrained ecosystem towards water-constrained ecosystem. The advancing peak growth over the eastern TP could significantly stimulate GPP, but this positive effect is weakened from 3.02 gCm^-2 year^-1 day^-1 during 2000s to 1.25 gCm^-2 year^-1 day^-1 during 2010s. Our results highlighted the importance of water availability in vegetation growth over the TP, and indicated that the TP grassland is moving towards a tipping point of transition from thermal-constrained to water-constrained ecosystem under a rapid warming climate.

How to cite: Liu, D., Meng, F., Xu, C., Wang, T., and Piao, S.: Shifts in the peak vegetation growth over Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2548, https://doi.org/10.5194/egusphere-egu24-2548, 2024.

Land surface temperature (LST) is a crucial physical parameter for hydrological, meteorological, climatological, and climate change studies. To encourage the use of satellite-derived LST products in a wide range of applications, providing feedback on product performance over regional and global scales is an urgent task. However, considering that the uncertainty of newly released LST products is still unclear, it is urgently necessary to perform a comprehensive validation and error analysis, especially in areas with special geographical and weather conditions such as the Tibetan Plateau (TP). In particular, fewer studies have been concerned with the degraded LST retrieval accuracy over the TP because of the sparse ground measurements. In this study, MODIS LST products (C6) were comprehensively evaluated based on independent ground observation systems with different atmospheric and LST conditions. The in situ measurements collected from the TORP and SURFRAD systems are located on the North American Plain and the TP, respectively, incorporating various land cover types, including barren land, grassland, cropland, shrubland and sparse and dense vegetation, among others. Prior to the validation, LST products with different spatial resolutions were compared to ensure the spatial representativeness of ground-based measurements at satellite pixel scale. The evaluation results indicated that relatively high-quality in situ LST can be obtained during nighttime with relatively homogeneous spatial distribution. Compared with the North American Plain (with a mean RMSE of 1.56 K), MODIS LST retrieval has larger discrepancies (mean RMSE of 2.34 K) over the TP with complex terrain and variable weather. Various factors affecting LST retrieval accuracy were analyzed, which were categorized into 1) the simulated atmospheric and surface temperature condition settings, 2) the input data uncertainty, and 3) others. Among them, the emissivity determination is the primary source of the uncertainty in the generalized split-window algorithm, where the overestimated emissivity causes an underestimation of LST. It is expected to develop new LST retrieval algorithm to meet the quality specifications of users over the TP. Overall, this study identifies critical further research needs and improve the understanding of LST product performance under complex circumstance.

How to cite: Qi, Y., Zhong, L., Ma, Y., Fu, Y., Wang, Z., and Li, P.: Evaluation of MODIS LST products over the Tibetan Plateau and plain areas with in situ measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3329, https://doi.org/10.5194/egusphere-egu24-3329, 2024.

The cryosphere has an important impact on regional water resources and ecosystems in the Chinese Altai
Mountains and its piedmont zone. Using the latest remote-sensing datasets of cryosphere changes and combining
with in-situ observation data from glacier monitoring stations and snow cover surveys, the main cryosphere
elements including glaciers, snow cover, and permafrost are investigated with emphasis on their changes since
2000 and the current situation. Their water resource effects are also discussed. The results indicate that although
the glaciers in the region have experienced continuous and intensive melting, mass loss has slowed because both
glacier area shrinkage and thickness reduction were larger during 2000–2010 than during 2010–2021. Snowcover
water equivalent (w.e.) has increased due to obvious increases in snow depth, although snow-cover
area has decreased slightly. Permafrost has been degrading. Overall, cryosphere contributions to the regional
water resource are approximately 40.9% since 2000, among which snow-cover melting is the largest, contributing
37.1% to water resources in the Irtysh River Basin and significantly more in the mountainous sub-basins
with increased snowfall. Glacier melting contributes 2.9%~3.4%, lower than earlier estimations of 3.4%
~3.6% for the late 20th century. Permafrost thaw caused by active layer thickening contributes approximately
0.59%. Meteorological data shows a warming and wetting trend, but summer temperature has a much lower
increase rate and a slowing increase trend after 2013. Moreover, snowfall frequency has increased. In the future,
glacier water resource contribution will continue to decrease, but the water resource effects of snow-cover
melting and permafrost degradation would increase.

How to cite: Wang, P.: Cryosphere changes and their impacts on regional water resources in the Chinese Altai Mountains from 2000 to 2021, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3711, https://doi.org/10.5194/egusphere-egu24-3711, 2024.

How to cite: Liu, Y.: Synergistic impacts of westerlies and monsoon on interdecadal variations of late spring precipitation over the southeastern extension of the Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2272, https://doi.org/10.5194/egusphere-egu24-2272, 2024.

The Southwest China vortex (SWCV) is that under the special terrain and circulation conditions of the Tibetan Plateau (TP), a meso-α-scale cyclonic low system with 300-500km horizontal scale at 700hPa or 850hPa in Southwest China. Being the important influencing system for the large area heavy precipitation in China summer half year, it is the second rainstorm weather system in China after typhoon in the intensity, frequency, and range of the caused rainstorms. So, SWCV and its weather influences are one of the main directions in Plateau Weather Science. And the research on the vortex source of SWCV has been always the key point of close attention.

The new related progresses in researches of the vortex source of SWCV system are reviewed for the last 10 years. In particular，it is recognized that because of the multi-scale effects between the topography and circulation，the vortex source of SWCV has the multi-scale characteristic of its distribution, and there are obviously differences between the structure、evolution、cause and influence of SWCV with the different vortex sources. The vortex sources of SWCV have closely connection each other. The upper-reach vortex sources such as Jiulong&Xiaojin have an important effect on the lower-reach vortex sources such as the Basin. The“effect of upper-reach vortex source”of SWCV, atmospheric gravity wave connecting with the complex topography，internal atmospheric process induced by precipitation, and the anomalous influences of East Asia monsoon are also the formation mechanisms for the vortex source of SWCV. And the formation of SWCV is mainly determined by the speed of incoming airflow in the direction of the main axis of the Hengduan Mountains. The formation vortex source of SWCV is mainly determined by the relative position of the incoming airflow in the windward area and the main axis of the Hengduan Mountains.

But, for research on the vortex source of SWCV, there are some problems such as being weaker in fine observation and basic data，being unknown for the multi-scale structures of the vortex source and its evolution, being not deep to understand the formation cause of different vortex sources and being incomplete in study of the SWCV evolutions and its effects of different vortex sources.

How to cite: li, Y.: The Related Researches of the Vortex Sourceof Southwest China Vortex Weather System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4952, https://doi.org/10.5194/egusphere-egu24-4952, 2024.

This study evaluated the monthly characteristics of TLRs based on the results derived from 18 observation stations in Bhutan (1996–2009), 56 stations in Nepal (1985–2004), and 53 observation stations in Pakistan (1971–2000). The study covers an elevation range of 5–3920 m above sea level, with various topography, climatic regimes, and geographical coordinates. Various empirical analysis techniques, including thermodynamics and hydrostatic systems, have been used to obtain the results. The annual cycle of TLR, such as a bi-modal pattern (two minima in the winter and summer and two maxima in the pre- and post-monsoon seasons), is a typical pattern throughout the study area. However, the forcing strengths, mechanisms, and processes for the monthly variations in TLR magnitude and diurnal range differed. Monsoon, orographic controls, and mountain barrier effects on TLR are more robust in summer, especially during the day, while the influences of inversions and mountainous microclimates are higher during the non-monsoon period, particularly in the winter and at night. A shallower TLR occurs in summer throughout the study area because of the intense heat exchange process within the boundary layer, corresponding to warm and moist monsoonal atmospheric conditions. Steeper values of TLR in the non-monsoon period, especially in the pre- and post-monsoon seasons, result from strong dry convective cooling at higher elevations owing to high thermal forcing effects at lower elevations. The winter shallower TLR is associated with westerly-driven cold air flow towards the lower elevations and radiative cooling, especially at night, excluding Bhutan. There are systematic differences in TLRs monthly and diurnal variations in magnitudes, such as the lowest gradient value in Pakistan observed in August and the highest in May, one month later than observed in Nepal and Bhutan, due to the late arrival of monsoon moisture in summer and intense thermal forcing effects following the wet early pre-monsoon months. In addition to the variation in magnitudes, the variation in the diurnal range from one place to another is also due to distinct differences in topoclimate, in addition to the effects of the synoptic regime, moisture amounts, elevations, geographical coordinates, variations in net radiation, surface roughness, vegetation coverage, and distance from the sea coast. The results of this study are useful for determining the local or regional climatic behavior or interactions, climate reconstruction, and temperature field in various glacial-hydro-climatic, ecological, and agricultural modeling.

How to cite: Kattel, D. B., Yao, T., and Ullah, K.: Evaluations of Temperature Lapse Rate in and Around the East-West Himalayan Chain: An Implication for Climate Understanding and Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3732, https://doi.org/10.5194/egusphere-egu24-3732, 2024.

The climate simulation over the Tibetan Plateau (TP) remains a challenge for climate models, limiting the reliability of future climate projections over there. This study focuses on the performance of regional climate models (RCMs) under the Coordinated Regional Climate Downscaling Experiment (CORDEX-II) in reproducing the climate over the TP, an overlapping regions that is encompassed by the CORDEX-EA, CORDEX-CA and CORDEX-WA, and assesses the uncertainty due to the choice of domain. The results show that all RCMs can capture the observed spatial distribution and annual cycle of temperature and precipitation over the TP, with overall cold and wet biases. Compared to the RCM itself, the choice of domain has little impact on the simulations, and such impact is larger in summer than in other seasons. Further analysis suggests that the downward shortwave radiation is the main contributor to the diverse temperature simulations among the RCMs for all seasons, and the underestimated number of wet days (R1mm) in the RCMs may be related to the lower frequency of 1-5mm rainfall. Furthermore, the effects of the choice of domain on precipitation simulation are mainly in the magnitude, while the effects on temperature simulation are mianly in the interannual variability.

How to cite: Niu, X. and Li, P.: Assessment of climate simulation over the Tibetan Plateau based on multidomain simulations within CORDEX-II, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4259, https://doi.org/10.5194/egusphere-egu24-4259, 2024.

A noticeable wet bias persists over the Tibetan Plateau (TP) during summer in both global and regional climate models, despite numerous advancements and ongoing efforts to lower it. This study investigates the performance of the Gaussian Probability Density Function (GPDF) cloud fraction scheme in the Weather Research and Forecasting (WRF) model over the TP during July and August 2018. The evaluation reveals that the GPDF scheme mitigates the wet bias over the TP in simulations at two resolutions (0.1° and 0.05°), with a significant reduction in the bias. This scheme also reduces the overestimation of downward surface shortwave radiation, indicating an improvement in cloud simulations. We propose that the GPDF scheme alleviates the wet bias through both local moisture process and dynamic process. Specifically, an increase in cloud water/ice content leads to a reduction in surface net radiation and subsequent decrease in surface sensible heat flux and evapotranspiration. This diminished surface heating lessens the thermal effect of the TP, causing a weakened monsoon circulation and decreased moisture flux convergence over the TP. Both the decreases in local evapotranspiration and remote moisture flux convergence contribute to the alleviation of the wet bias, and the latter plays a dominant role, contributing to approximately 70% of the precipitation decrease.

How to cite: Liu, J., Yang, K., Zhao, D., Wang, J., Zhou, X., and Lin, Y.: Implementing Gaussian Probability Density Function cloud fraction scheme in WRF much reduces the wet bias over the Tibetan Plateau in high-resolution simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3727, https://doi.org/10.5194/egusphere-egu24-3727, 2024.

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

How to cite: Li, R., Xu, X., Xu, X., Shepherd, T. G., and Wang, Y.: Importance of orographic gravity waves over the Tibetan Plateau on the spring rainfall in East Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9287, https://doi.org/10.5194/egusphere-egu24-9287, 2024.

The Qilian Mountains, a series of marginal mountains in the northeastern part of the Tibetan Plateau (TP), are a vitally important ecological protection barrier in the northwestern arid areas. In order to improve understanding of the microstructure of precipitation, the characteristics of raindrop size distribution (DSD) were analyzed using the Second Tibetan Plateau Comprehensive Scientific Expedition of observations. The Qilian Mountains region has its own unique DSD characteristics with a smaller raindrop diameter and a higher number concentration (3.69 for log₁₀N_w and 0.94 mm for D_m) comparing with eastern, southern, northern, and central China, but are similar to those of southeastern TP. For all rainfall events, the number concentrations of small and large raindrops in the interior and on the southern slopes were greater than on the northern slopes, but midsize raindrops were less. The DSD spectrum of the interior was more variable and differed significantly from that of the northern slopes. The differences in the normalized intercept parameters of the DSD for stratiform and convective rainfall were 8.3 % and 10.4 %, respectively, and those of the mass-weighted mean diameters were 10.0 % and 23.4 %, respectively, while the standard deviations of DSD parameters at interior sites were larger. The differences in the coefficient and exponent of the Z–R relationship were 2.5 % and 10.7 %, respectively, with an increasing value of the coefficient from the southern to the northern slopes for stratiform rainfall but the opposite for convective rainfall. In addition, the DSD characteristics and Z–R relationships were more similar at the ipsilateral sites and had smaller differences between the southern slopes and interior of the mountains

How to cite: Mao, W., Li, G., and Zhang, W.: Statistical characteristic differences of raindrop size distribution during rainy seasons in the Pan Third Pole region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9706, https://doi.org/10.5194/egusphere-egu24-9706, 2024.

The High-Asia (HA), which includes the Tibetan Plateau (TP), Iranian Plateau (IP) and Mongolian Plateau (MP), is experiencing a warming rate that is twice the global average. The increasing temperature is causing significant changes in thermal conditions across the HA and surrounding regions, which may further affect China's summer precipitation. This study used datasets from the ERA5-Land reanalysis and the high-resolution China Meteorological Forcing Data to investigate variations in SH over three plateaus of HA, and to explore the relationship between these variations and changes in China's summer precipitation. The results indicate that variations in summer SH of the HA are the largest, making them the primary contributor to the annual mean values. The summer SH over TP exhibited a decreasing trend from 1979 to 2021 (-0.47 W m^-2 decadal^-1, p<0.05), in contrast with the trends in IP and MP (0.59 and 1.46 W m^-2 decadal^-1, respectively, p<0.05). Additionally, based on the empirical orthogonal unfolding method, the dominant SH pattern over the HA revealed that the variation over the TP was opposite to that over IP and MP, and this pattern experienced a significant interdecadal shift in 1999. Moreover, The initial leading temporal expansion series of singular value decomposition showed a consistent trend in SH over the HA and summer precipitation in China (correlation coefficient=0.85, p<0.05), and an abrupt change was observed during 1998-1999. The dominant spatial pattern demonstrated that interdecadal drought in the northeast China and the Yangtze River valley exhibited a significantly positive correlation with the leading SH pattern over the HA. Conversely, increased precipitation in the northwest and south of China showed a negative correlation. Our study suggests a link between SH over HA and China's summer precipitation, providing new insights into understanding the mechanisms underlying changes in China's summer precipitation.

How to cite: Yao, N., Ma, Y., Li, X., and Peng, J.: Variations in sensible heat flux of High-Asia and their relationship with China's summer precipitation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5720, https://doi.org/10.5194/egusphere-egu24-5720, 2024.

Aridity change in the Northern Hemisphere (NH) is a vital topic in exploring climate change. The Tibetan Plateau (TP) is essential for its role in climate variability over the NH. We applied the ensemble empirical mode decomposition (EEMD) to the aridity index (AI) from 20°-60°N in this study. The EEMD method extracts a set of intrinsic mode functions (IMFs) with various timescales. Results from our analysis reveal that the multi-decadal oscillation of AI makes 35% contribution to the variability of the AI. And the multi-decadal oscillation of the TP thermal forcing makes 18.15% contribution to the multi-decadal variability of the AI, which is often ignored in previous studies. The dynamic and thermal effects of the TP also affect the AI change, which illustrates a mode of meridional difference around 40°N, with wetting in the north and drying in the south. Meanwhile, the dynamic effects of the TP lead to latitudinal difference north of 40°N in Asia, with drying Northeast Asia. Such meridional and latitudinal differences over South Asia, Southeast Asia and southern China are controlled by a high-pressure system from 850 hPa up to 500 hPa, which results in an increase of sinking motion from 20°-40°N with obvious continuous drying effect.

How to cite: Gao, Z., Guan, X., He, B., Zhao, L., Xie, Y., He, Y., and Ji, F.: Impacts of the Tibetan Plateau on aridity change over the Northern Hemisphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3167, https://doi.org/10.5194/egusphere-egu24-3167, 2024.

Permafrost is a key component of the cryosphere, which plays significant roles in surface energy, hydrological, and biogeochemical processes. Moreover, permafrost, a sensitive indicator of climate change, has experienced widespread degradation in recent decades. The Tibetan Plateau, hosting the largest mid-low latitude permafrost area, is particularly susceptible to these changes, warranting a deeper understanding of permafrost distribution and environmental interactions. However, permafrost mapping traditionally relies on empirical and physical models, each with its set of advantages and drawbacks. Empirical models, while user-friendly, introduce uncertainties due to data quality and scale issues. On the other hand, physical models, offering precision, demand high-quality data and face challenges in extensive simulations over large areas. With the advancement of artificial intelligence technologies, machine learning has rapidly formed many implementation algorithms and been applied in different fields. Permafrost mapping has been investigated with a variety of machine learning algorithms (i.e., neural networks, support vector machines, random forest, and gradient boosting), and demonstrated superior accuracy over traditional methods when applied to large areas, especially when there are abundant training data available.

Despite these advancements, challenges persist, notably in mountainous areas characterized by scarce in situ data and complex topography. This study proposes a novel approach involving rock glaciers as valuable indicators for permafrost mapping. Intact and relict rock glaciers, representing the presence or absence of permafrost, offer crucial insights, particularly in mountainous regions where traditional methods fall short. The study focuses on the Qilian Mountains, a representative mountainous area on the Tibetan Plateau. Leveraging machine learning and rock glaciers, the research aims to simulate the Permafrost Zonation Index (PZI). Rigorous accuracy evaluations and comparisons with existing permafrost maps are conducted, promising a nuanced understanding of permafrost dynamics in this challenging terrain. The integration of technological advancements and innovative approaches holds the potential not only to advance permafrost research but also to inform conservation strategies and climate change assessments on a broader scale.

How to cite: Feng, M., Yan, D., Hu, Z., and Xu, J.: Enhancing mountainous permafrost mapping by leveraging rock glacier inventory, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10319, https://doi.org/10.5194/egusphere-egu24-10319, 2024.

The Third Pole (TP) represent the largest alpine mountains on Earth. Its cryosphere is shrinking and collapsing and the hydrosphere is subsequently expanding under a warming climate in recent decades, posing potential impacts on biogeochemical cycles. In particular, the carbon cycles there have experienced dramatic changes, primarily with the alterations of cryosphere and hydrosphere. Carbon emissions from the melting glaciers and thawing permafrost can further trigger feedback on climate change. However, their current status and future fate in this region still need clarification comprehensively. Here, we review the current state of carbon stocks in the changing TP cryosphere and hydrosphere, focusing on their variations in permafrost, glaciers, and related inland waters (upper river streams, thermokarst lakes, and glacial lakes). We also considered their release pathways and the amounts of carbon released into aquatic ecosystems and the atmosphere. Finally, we recommend research priorities to address dynamics in carbon cycling and possible future impacts on the TP. This review will highlight the important of dynamics of carbon cycle on the TP under climate change in future.

How to cite: Zhang, Y. and Gao, T.: Carbon dynamics shift in changing cryosphere and hydrosphere of the Third Pole, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1929, https://doi.org/10.5194/egusphere-egu24-1929, 2024.

The foreland of the Uisu Glacier, located in NE Pamir, is characterized by a combination of processes typical for periglacial and hyperarid areas. Therefore, the development of vegetation and soils is significantly hampered there, with soil organic carbon pools being among the lowest reported worldwide (1.4 kg m^-2 in the layer 0-50 cm). Given the extreme environmental conditions in the investigated area, we expected that (1) biological soil crusts (BSCs) of different developmental stages comprise the dominant part of the biologically active soil cover; and hence (2) play an important role in the accumulation of C, N and P, with the microbial biomass and total nutrient retention patterns positively related to their developmental stage. To assess the potential importance of BSCs for nutrient accumulation processes in soils of the study area, we compared the C, N, and P enrichment in soils under the BSCs with the same parameters in soils under vascular plants. Subsequently, we studied C, N and P accumulation in the soils from six distinct plant communities recorded in the foreland.

Our study showed that BSCs dominated in five out of ten study plots with recorded biologically active soil cover. Among them prevailed poorly developed morphotypes (no lichens, no bryophytes) with a mean coverage of 14%. Compared to advanced crusts (mean coverage 1.1%), they accumulated less total C, N and available P in their biomass. Yet, they were still the main biological soil-forming factor next to the plants (mean coverage of 8.6%) in our study site, given that stones and non-crusted bare soils covered most of the area (joint mean coverage over 80%). Soil-forming properties of both poorly developed and advanced crusts were confirmed by the observed enrichment of their sub-crust soils in total C, N and available P in comparison to non-crusted bare soils (on average, there were ~1.5 times more nutrients in soils under poorly developed crusts and ~2.5 more nutrients in soils under advanced crusts than in non-crusted bare soils). Moreover, the average enrichment observed for soils under advanced crusts was similar to the results obtained for soils under individual vascular plants from the same study plot (~2.5 times more than in non-crusted bare soils).

The large-scale studies of soils from the identified plant communities showed that only in three of them C and N amounts were higher than in the respective bare soils. Phosphorus content was similar in all the studied communities, with values approximately two times higher than for bare soils. Statistical analyses showed that the amount of C, N and P was strongly positively correlated with the percentage coverage of plants and with species diversity of the community (expressed as Shannon Wiener index and as a number of species).

As further aridification is projected for the Pamir, leading to the limitation of ecological niches available for vascular plants, BSCs could potentially become the most important or even the sole player in the accumulation of soil nutrients in many areas.

This work was supported by the Polish National Science Centre Grant No 2017/25/B/ST10/00468.

How to cite: Mętrak, M., Wilk, M., Jasser, I., Chachulski, Ł., Korabiewski, B., and Suska-Malawska, M.: Nutrient accumulation by biologically active soil cover in a dry, high-altitude glacier foreland in the NE Pamir (Tajikistan) in the context of ongoing climate changes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7292, https://doi.org/10.5194/egusphere-egu24-7292, 2024.

As a solid reservoir, glaciers play a significant role in regulating the variation of runoff abundance and dieback in the form of “peak-cutting and valley-filling”. The hydrological regulation function of glaciers is very important in cold regions, especially in the arid regions of Northwest China. The runoff estimation data from 2014 to 2100 were simulated by the VIC-CAS model in the cold region of western China. With perspectives of combinations of trend and fluctuation characteristics, glacier hydrological regulation index (Glacier _R) was constructed based on the runoff variation coefficient method to analyze the stability of glacier runoff in 9 cold region basins of western China. The changes of the hydrological regulation function of glaciers in these basins are analyzed in detail during the historical period (1971–2010) and in the future to the end of the 21st century. The results show that: In the historical period and under the RCP2. 6 and RCP4. 5 scenarios, except for the Yangtze River basin, the decrease time node of glacier runoff in other basins of the Tibetan Plateau is 2020s, and that in the northwest inland basins is 2010s. In historical period and under the global emission scenarios of RCP2. 6 and RCP4. 5 to the end of the 21st century, although the glacier runoff in most of cold region basins in western China showed a decreasing trend, the fluctuation range decreased or had no obvious change, and the stability of glacier runoff increased or had no change. Overall, hydrological regulation function of glaciers is high in the northwest inland river basins, while function is low in the basins of the Qinghai-Tibet Plateau. Under the global emission scenarios of RCP2. 6 and RCP4. 5, to the end of the 21st century, the hydrological regulation function of glaciers showed a weakening trend in all cold region basins of western China, and the weakening was more significant in the inland river basins of Northwest China. Under the global emission scenario of RCP4. 5,the hydrological regulation function of glaciers in the Muzati River decreased by 25. 4%, and all the basins of the Qinghai-Tibet Plateau remained at a low level. With the perspective of decadal variation, the hydrological regulation function of glaciers in the cold region basins of western China was strong during the period of 1970s–2010s, especially in the 1980s and 2000s. Under the global emission scenarios of RCP2. 6 and RCP4. 5, the hydrological function of glaciers showed a weakening trend obviously in the future to the end of 21st century. The earliest time node in the cold region basins is 1970s, and the latest is 2020s.

How to cite: Yang, J. and He, Q.: Future change of hydrological regulation function of glaciers in the cold region basins of western China , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2441, https://doi.org/10.5194/egusphere-egu24-2441, 2024.

The occurrence of cloud directly affects the spatial and temporal continuity of surface temperature inverted by satellite remote sensing. In this study, a framework for reconstructing surface temperature with high spatial and temporal resolution based on data assimilation is constructed on the basis of multiple subsurface validation. (1) The accuracy of MYD11A1 LST data varies with terrain and land cover characteristics. High-altitude alpine terrains (Kalasai and Arou) and undulating desert terrains (Tazhong A-E Sites) show high precision and less error, while agricultural fields (Daman) and desert transitional zones (Bajitan) exhibit more variability and larger errors. This suggests that the uniformity and stability of certain terrains, coupled with minimal atmospheric interference, enhance the accuracy of remote sensing observations. (2) A systematic bias, indicating a consistent underestimation of LST by the MYD11A1 product compared to ground-based observations, is observed across all sites. This bias is particularly pronounced in the presence of a sanding phenomenon, which results in a mixture of sand and air near the surface, leading to a lower station observation and a significant bias. (3) The Land Surface Temperature (LST) simulated by noah-MP exhibits a high degree of consistency with the LST observed through remote sensing. The significant correlation between the simulated LST and MODIS observations at the Kalsai and Arou stations indicates that noah-MP is highly applicable to mountain grassland surfaces. (4) A framework has been developed for reconstructing surface temperature with high temporal and spatial resolution, based on data assimilation. This method can generate all-weather, hourly surface temperature data.

How to cite: Li, Y., Qing, H., Wang, X., and Yan, Y.: Establishing a Framework for Assimilating Satellite Observations with Land Surface Process Models to Obtain Time-Continuous 1km High Spatial Resolution Surface Temperature: A Case Study of the Kunlun-Altunshan-Qilian Mountain Region , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20234, https://doi.org/10.5194/egusphere-egu24-20234, 2024.

Seasonal freezing and thawing of the active layer in permafrost regions generally induce surface deformation that interferometric synthetic aperture radar (InSAR) can monitor on regional scales. InSAR has been widely used for detecting changes in active-layer thickness (ALT), an indicator of permafrost thaw. Previous studies have shown that the depth of the active layer and its soil water content have a strong influence on the magnitude of the surface deformation, and a linear relationship between ALT and surface deformation is often assumed in poorly drained Arctic soils. However, in dry areas such as the Tibetan Plateau permafrost region, the relationship between ALT and deformation is more complex and challenging to elucidate.

To examine the relationship in the Qinghai-Tibetan permafrost region, this study synthesizes InSAR-derived surface deformation data, multispectral measurements from unmanned aerial vehicle (UAV) sensors, and in-situ soil temperature and moisture data along a ~930-km transect. Our analyses reveal that seasonal deformation generally increases with ALT (R=0.74, p=0.26) at sites with moderate to dense vegetation cover (summer NDVI>0.5), aligning with previous research. However, at sites with sparse vegetation (summer NDVI<0.5), a strong negative correlation was found between the seasonal deformation and ALT (R=-0.83, p=0.01). Those areas are generally associated with deep active layers and low surface soil moisture. Among all sites, seasonal deformation shows a stronger correlation with the soil moisture content of the lower portion of the active layer (R=0.77, p=0.006), but a weak correlation with either surface or profile soil water content (R<0.20，p>0.60). This study provides insights into the non-linear relationship between deformation and ALT in arid and semi-arid permafrost regions such as the Tibetan Plateau, allowing for accurate active-layer estimates and soil water dynamics in this region.

How to cite: Chang, T., Yi, Y., Jiang, H., Zwieback, S., and Li, R.: Unraveling the non-linear relationship between surface deformation and active layer thickness in the Qinghai-Tibetan permafrost region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13817, https://doi.org/10.5194/egusphere-egu24-13817, 2024.

Per- and polyfluoroalkyl substances (PFASs) are one of emerging pollutants of international concern. They are ubiquitous worldwide, even in remote polar and alpine regions. Benskin et al. (2011) proposed that direct long-range atmospheric transport (LRAT) of PFASs, atmospheric transport and degradation of their precursors are the main sources of PFASs in remote regions. Chen et al. (2019) found in their study of PFASs in the water and surrounding runoff of Lake Nam Co in the Tibetan Plateau that the release from glacier melting is the second largest source after LRAT. As the continuous production and use of PFASs, combined with the impact of glacier melting, the concentrations of PFASs in Lake Nam Co are likely to rise rapidly. In this study, a total of 38 lake water samples were collected from Lake Nam Co in August 2023, and a total of 30 runoff water samples from glacial and non-glacial runoff flowing into Lake Nam Co were collected and the concentrations of 9 PFASs were analyzed. By comparing with the results of 2020, the temporal trend of PFASs in Lake Nam Co was studied, and their potential sources were analyzed. The results show that the mean concentration of PFASs in the water samples collected from the shores of Lake Nam Co in 2023 is 7724 pg/L, which is a 120% increase from the level observed in 2020. Within the PFASs, the short-chain PFASs (4-6 carbon atoms) exhibit the fastest growth, increasing by 150% compared to 2020. This may be due to the widespread production and use of short-chain PFASs as substitutes for long-chain PFASs, which arrive in Lake Nam Co via LRAT, resulting in a more significant increase in the concentrations of short-chain PFASs in the lake water. It is also found that the concentrations of PFASs in glacial runoff are significantly higher than in non-glacial runoff, with the greatest concentration difference found for PFBA, which is approximately twice as high in the glacial runoff compared to non-glacial runoff. In addition, the concentrations of PFASs in the southern side of Lake Nam Co, which receives multiple glacial runoff inputs, are higher than those in the northern side, with PFBA showing the greatest difference between the two sides. Several studies have speculated that PFBA may be an indicator of ice and snow melting. The observed spatial heterogeneity of PFBA implies that the release of PFASs due to glacier melting could be one of the main sources contributing to the increasing concentrations of PFASs in the water of Lake Nam Co. Under the influence of global warming, the glaciers surrounding Lake Nam Co may experience further melting in the future, which implies that the melting of glaciers could release more PFASs into Lake Nam Co in the coming years. Given that the concentrations of PFASs in the water of Lake Nam Co have shown an increasing trend, it is necessary to conduct continuous tracking monitoring and environmental risk assessments for Lake Nam Co and other ecologically vulnerable environments such as alpine and polar regions.

How to cite: Peng, L., Wu, J., Yu, Y., Wang, T., Zhuang, Y., and Liu, Z.: Concentrations variation trend and potential sources of PFASs in Lake Nam Co, Qinghai-Tibet Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13725, https://doi.org/10.5194/egusphere-egu24-13725, 2024.

Chemical weathering plays a crucial role in the long-term evolution of Earth’s climate, yet the spatial heterogeneity of the weathering rate and intensity driven by glacial erosion owing to glacial shrinkage worldwide is poorly constrained. Here we develop a global data set of cation denudation rate (CDR) and intensity (CDI) from mountain ranges, glacial regions and glacial catchments worldwide. Contemporary weathering rate and intensity are ~ 2 times higher than two decades ago, 2 ~ 6 times higher than Greenland ice sheet basins and over 2 times higher than whole ice sheet means. Their spatial patterns are characterized by relatively high weathering rate and intensity in low latitudes in contrast to low weathering rate and intensity in high latitudes. This is closely related to glacial erosion involving with temperature, precipitation, discharge, altitude and slope, suggesting that the element mobilization and CO₂ budgets caused by glacial chemical weathering are likely to enhance in a warming landscape. We contend that subglacial chemical weathering is far more important than previously thought and should be considered in elemental cycles and carbon cycling.

How to cite: Li, X., Wang, N., Ding, Y., Wang, R., Raiswell, R., Zhang, S., Liu, Q., He, X., Han, H., Han, T., Yu, Z., Mitchell, A. C., and Yi, T.: Global chemical weathering patterns set by glacial erosion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7545, https://doi.org/10.5194/egusphere-egu24-7545, 2024.

Subglacial drainage system plays a central role in regulating chemical weathering processes in glacier environments. However, the influence of glacial drainage systems’ seasonal evolution on chemical weathering processes and consequent carbon sink effect is still unclear. This study selected the Parlung No. 4 Glacier in the southeast Tibetan Plateau (TP) and Kuoqionggangri Glacier in the central TP as the study areas, representing the typical temperate glacier and polar glacier, respectively. Sampling campaigns were conducted during the initial ablation period of those two glaciers when glacial drainage systems may undergo significant transformation. River water samples were collected almost daily for glacial runoff and 5-day intervals for outlets of the catchments. Evidences from tracer tests and Ca^2+*/SiO₂^* show that glacial drainage system of the Kuoqionggangri Glacier is quite constant and it is dominated by a supraglacial pattern (^* represents ionic concentration after atmospheric inputs correction). Subglacial drainage system of the Parlung No.4 glacier, however, transferred from a supraglacial pattern during the early monsoon season to a channelized pattern after June 25^th. Cationic budget and major anionic sources discrimination (HCO₃^-) show that chemical weathering processes in the polar glacial catchment (Kuoqiongqu) has been displaying minor temporal change even though water discharge experienced a 7 times increment. Nevertheless, carbonate dissolution in the temperate glacial catchment (Rinongqu) was 24% decreased but sulfide oxidation 23% increased with the elapse of monsoon season. Its DIC (equivalent to HCO₃^-) sources from biological CO₂ are 10% higher in early (before May 21^st) and late monitoring periods (June 26^th to July 10^th) while the input proportion of atmospheric CO₂ shows an opposite temporal change with 12% higher proportion from May 22^nd to June 25^th. The seasonal change of net CO₂ consumption rate caused by chemical weathering (ФCO₂_net) in the Kuoqiongqu catchment is positive correlated with water discharge, indicating carbon sink effect in the polar glacial catchments of the central TP is mainly governed by water discharge. ФCO₂_net in the early subglacial channels reopen period is even slightly lower than that from April 2^nd to May 10^th when water discharge is more than 2.4 times lower because of dramatic increases in CO₂ release rate caused by sulfuric acid dissolve carbonate (ФCO₂_sul). This study highlights the evolution of glacial drainage system exerted crucial effects on carbon cycle by regulating chemical weathering processes.

How to cite: Yu, Z.: Contrasting variations of chemical weathering processes during the initial ablation period in two different glacial drainage systems, Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9127, https://doi.org/10.5194/egusphere-egu24-9127, 2024.

The land surface heat flux is a crucial parameter that plays a significant role in the transformation and cycling of energy and matter between the atmospheric and land surface layers. This parameter serves as an essential input for various numerical models. Most land surface schemes deduce soil heat flux by amalgamating the heat conduction equation and residual method of energy balance. However, substantial discrepancies could be observed in soil heat flux simulations. These occurred among different Numerical Weather Prediction and offline Land Surface models, even though they were driven by the same atmospheric processes. The presence of discrepancies in models necessitated the accurate calculation of soil heat flux in order to reduce uncertainty in the allocation of sensible and latent heat flux at the surface. By reducing this uncertainty, we could decrease uncertainties in surface energy partitioning, achieved through diminishing the bias in simulated precipitation. However, in the Tibet plateau, soil heat flux observations were sparsely distributed, and the coverage period was different and limited, primarily used for model and remote sensing validation. There was a notable gap in research on the precise variations in soil heat flux in the Tibet plateau, particularly in studies employing sampled soil observations to accurately calculate soil heat flux. This study addressed these aforementioned deficiencies by focusing on soil attributes in the Tibet plateau to accurately calculate soil heat flux. In calculating soil heat flux precisely, factors like topography, land use, and vegetation type were considered. To ensure stability, representative soil cores were carefully observed and selected, obtaining samples through a layer-by-layer sampling approach. All sampling work had currently been completed.

Utilizing comprehensive, synchronous, and continuous soil heat flux observations at the BJ site, in conjunction with long-term observational data and soil samples, we employed sampled soil attributes and soil heat flux plate observations to ascertain the requisite parameters for accurate soil heat flux calculation. These parameters, including the physical properties and porosity of soil profiles, enabled us to precisely determine the surface soil heat flux fluctuations at the BJ site. As a result of global warming, the Nagqu region had experienced elevated temperature, augmented precipitation, and amplified soil heat flux. In summary, accurately calculating soil heat flux is vitally important for allocating sensible and latent heat flux at the surface, which in turn diminishes uncertainty in the surface energy balance within models. This reduction in uncertainty is crucial for establishing a foundation to mitigate biases in local precipitation simulations within existing models.

How to cite: He, J., Ma, W., Ma, L., Ma, W., and Shi, L.: Accurate calculation of Land Surface Heat Flux Based on Soil Observations over the Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3341, https://doi.org/10.5194/egusphere-egu24-3341, 2024.