The Tibetan Plateau, known as the Earth's largest and highest plateau, functions as a crucial nexus for global atmospheric processes. It exerts a pivotal influence on the hydroclimate dynamics of East Asia. Nevertheless, achieving a comprehensive understanding of historical and recent hydroclimate variations, along with their far-reaching ecological and societal impacts, has proven to be a formidable challenge due to limited observational data and uncertainties in proxy reconstructions. In this study, we have reconstructed the precipitation changes in the eastern Tibetan Plateau over the past 2000 years based on tree-ring δ¹⁸O data. This reconstruction emerges as a reliable proxy for precipitation changes in the central and eastern regions of China. Further research found that our precipitation reconstruction of the Tibetan Plateau unveils coherent variations between the Asian monsoon and the Westerlies.
How to cite: Liu, Y.: Hydroclimate variations on the Tibetan Plateau over the past 2000 years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7563, https://doi.org/10.5194/egusphere-egu25-7563, 2025.
The Tibetan Plateau (TP) is also known as the ‘Water Tower of Asia’ as it is the source of 10 major rivers. Significant changes in the natural and social environment of the TP have occurred over the last 50 years (e.g., temperatures have warmed twice as much as the global average over the same period), and there is considerable uncertainty about future environmental change. Water vapor flux, expressed as evapotranspiration (ET), is crucial for understanding the water balance over the TP. The TP is rich in land cover types, including grasslands, deserts, lakes, forests, glaciers, snow, etc. The dynamics and thermodynamics of the subsurface vary greatly between different climate types, making it a major challenge to conduct large-scale studies of ET processes over the TP and to explore the governing mechanisms and feedbacks to the climate system and hydrological processes. However, a single ET dataset cannot provide a reliable answer on how much water is evaporated from the TP due to model limitations in describing complete processes and uncertainties in different datasets. In this study, we first evaluated 22 ET products in the TP against in-situ observations and basin-scale water balance estimates. The spatiotemporal variability of the total vapor flux was also evaluated to clarify the vapor flux magnitude and variability over the TP. The results showed that the high-resolution (~1km) global ET data based on observations from ETMonitor and PMLV2 were more accurate than than other global and regional ET data with fine spatial resolution (~1km), when comparing with in-situ observations. When compared with basin scale water balance estimates of ET, ETMonitor and PMLV2 at finer spatial resolution and GLEAM and TerraClimate at the coarse spatial resolution showed good agreement. Different products showed different patterns of spatiotemporal variability, with large differences in the central to western TP. The mean water vapor flux over multi-year and multi-product over the TP was 333.1 mm/yr with a standard deviation of 38.3 mm/yr. Soil evaporation accounts for most of the total water vapor flux over the TP, followed by plant transpiration and canopy rainfall interception evaporation, while the contributions from open water evaporation and snow/ice sublimation are not negligible.
How to cite: Jia, L. and Zheng, C.: Assessing how much water evaporated from the Tibetan Plateau using multiple datasets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19923, https://doi.org/10.5194/egusphere-egu25-19923, 2025.
Permafrost degradation on the Qinghai - Tibet Plateau (QTP) have a direct impact on the evapotranspiration and moisture recycling process by changing underlying land surface conditions. Up to now, the contribution of thermokarst lake evaporation and plant transpiration to local precipitation in the permafrost regions of the QTP remains unknown. This study collected precipitation, thermokarst lake water, plant, and soil samples, and quantitatively estimated the proportional contributions of thermokarst lake evaporation, soil evaporation, and plant transpiration to local precipitation by the Bayesian isotopic mixing model in the permafrost region of central QTP. Results showed that the contribution of advection vapor to local precipitation was dominant, with a mean value of 74.6 %, and the moisture recycling ratio ranged from 19.7 ± 2.1 % to 29.7 ± 3.6 % (mean: 25.4 %). The mean contribution fraction of thermokarst lake evaporation and soil evaporation were 9.2 % and 8.9 %, respectively. Contrary to the findings of related studies in the nearby Qilian Mountains and arid central Asian oases, the total surface evaporation contribution of 18.1% was considerably higher than the 7.4% of plant transpiration in this study area, which was attributed to the rapid expansion of thermokarst lakes, sparse vegetation, and higher soil moisture condition in the shallow active layer.
How to cite: Wu, T. and Zhu, X.: Larger contribution of evaporation from soil and thermokarst lake to local precipitation than plant transpiration in the permafrost regions of central Qinghai-Tibet Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14353, https://doi.org/10.5194/egusphere-egu25-14353, 2025.
The Yarlung Zsangbo Grand Canyon (YGC) is one of the world's deepest canyons. In this sparsely gauged region, remotely sensed precipitation products can be valuable. A new rain gauge network was installed in the YGC in November 2018, and the observations were utilized to evaluate and calibrate the Integrated Multi‐satellite Retrieval for Global Precipitation Measurements (IMERG) precipitation product. The evaluation results demonstrate that the IMERG data reasonably captured the observed seasonal and diurnal variations in the precipitation but with much weaker seasonal and diurnal variations. IMERG underestimated the total rainfall primarily due to under-detection of rainfall events, with misses being more prevalent than false alarms. 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. The probability of detection decreased with elevation, leading to increased underestimation of rainfall events at higher elevations, and the false alarm ratio was higher in valley sites. In terms of the hit events, IMERG overestimated the light rainfall events and underestimated the heavy rainfall events and the negative bias in the hit events decreased with elevation. The GPCC calibration partially improved the underestimation of GPM, but not sufficient. This study fills the gap in IMERG validation in a complex mountainous region and has implications for users and developers.
How to cite: Chen, X.: Evaluation of the GPM IMERG product in the Yarlung Zsangbo Grand Canyon of the eastern Himalaya, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1252, https://doi.org/10.5194/egusphere-egu25-1252, 2025.
Significant progress has been made in understanding the relationship between Tibetan Plateau (TP) summer precipitation and the summer North Atlantic Oscillation (SNAO). However, the role of topography on this relationship remains unclear. The central-eastern Himalayas (CEH), a key high-altitude barrier on the southern edge of the TP, experiences concentrated summer rainfall and is a crucial water source. Analysis of long-term observations and reanalysis data revealed that the SNAO-driven positive summer precipitation in the CEH was influenced more by topographic mechanical forcing than by the impacts of atmospheric circulation. Topography forces horizontal winds to generate a strong climb flow component, driving changes in the precipitation distribution. Experiments removing topographic features show that the original positive precipitation distribution shifts into a dipole-like pattern, dominated by negative distribution, which are directly governed by atmospheric circulation. Thus, accurate predictions of future summer precipitation in the CEH should consider both dynamic topographic and atmospheric processes.
How to cite: Zhang, Q., Chen, X., and Ma, Y.: Topographic Influence on SNAO-Driven Summer Precipitation Variability in the Central-Eastern Himalayas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5931, https://doi.org/10.5194/egusphere-egu25-5931, 2025.
The Tibetan Plateau, as the source of major rivers in Asia, plays a critical role in influencing the ecological environment, production, and livelihoods both within the region and downstream. Consequently, enhancing the accuracy and efficiency of extreme weather forecasting in this area is of paramount importance. This study introduces a lightning data assimilation scheme that utilizes the Fengyun-4A Lightning Mapping Imager and the Advanced Direction Time Lightning Detection System (ADTD) flash extent density to assign a pseudo-relative humidity between the cloud base and a specific atmospheric layer. This study evaluates the performance of pseudo-relative humidity assimilation for short-term severe weather forecasting over the central-eastern Tibetan Plateau. The high impact severe weather event that occurred in Datong, Qinghai on 18 August 2022 is used as a case study to compare the effectiveness of lightning data assimilation with assimilation of ground, sounding and radar data for forecasting deep convection in Tibetan Plateau.
How to cite: An, J., Chen, S., and Hu, Z.: Assimilating FY-4A Lightning and Radar Data for Improving Forecasts of a High-Impact Convective Event in the Central-Eastern Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7606, https://doi.org/10.5194/egusphere-egu25-7606, 2025.
In this study, fifth major global reanalysis produced by ECMWF (ERA5) reanalysis data from 1979 to 2022 were utilized to investigate extreme precipitation in the central Asian high mountain (CAHM) region, comprising the Pamir Plateau and western, central, and eastern Tianshan regions. This study found that westerlies and monsoons are the primary drivers of extreme precipitation, with distinct mechanisms in the southwestern and northeastern CAHM (divided at approximately 79oE). In the southwestern CAHM, a weak Indian summer monsoon (ISM) leads to negative potential height anomalies, enhancing meridional water vapor flux from the Bay of Bengal and Arabian Sea, thereby increasing precipitation. Conversely, extreme precipitation is associated with the negative phase of the Silk Road pattern in the northeastern CAHM. While the East Asian summer monsoon (EASM) plays a lesser role, it influences water vapor supplies and atmospheric circulation in the southwestern CAHM and modulate meridional wind position in the northeastern CAHM with the ISM, contributing to extreme precipitation. Seasonal analysis revealed May as the peak for extreme precipitation in the southwestern CAHM region, while extreme precipitation in the northeastern CAHM region peaked in the midmonsoon months (June and July) due to the synergy between monsoons and westerlies of different strengths passing through the CAHM.
How to cite: Zhao, W., Ma, Y., Takemi, T., Chen, X., and Cao, D.: Investigating the Underlying Mechanisms of Monsoon Season Heavy Precipitation in Central Asian High Mountain Areas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14093, https://doi.org/10.5194/egusphere-egu25-14093, 2025.
The Tibetan Plateau is renowned for its complex topography and heterogeneous surface, which lead to uneven surface heating and, consequently, trigger various local circulation phenomena such as valley winds, glacier winds, and lake-land breezes. To more accurately capture these unique meteorological conditions and improve wind field simulations in complex terrain, this study introduced and compared six different boundary layer parameterization schemes to evaluate their performance in simulating the wind field in the regions of the Lake Nam Co and Mount Everest. The study utilized two three-dimensional boundary layer schemes: SMS-3DTKE and PBL3D; two variations of SMS-3DTKE—one with simplified horizontal diffusion (3DTKE_smag) and another with the horizontal diffusion term completely removed (3DTKE_0); and two traditional one-dimensional boundary layer schemes: MYNN and Shin-Hong. Observed data was used to validate the simulation results. The results indicated that the two three-dimensional boundary layer schemes provided wind profiles at the Qomolangma Atmospheric and Environmental Observation and Research Station, CAS (QOMS) that closely matched observations, significantly outperforming the one-dimensional schemes. In particular, the three-dimensional schemes not only successfully simulated the near-surface wind field and the wind characteristics at 500 meters, but also explained the mechanism behind the afternoon strong winds—caused by the convergence of westerly winds crossing the ridge and southwesterly winds in the Rongbuk Valley. Furthermore, the SMS-3DTKE scheme excelled in simulating the onset time and intensity of the lake breezes at the Nam Co Monitoring and Research Station for Multisphere Interactions, CAS (NAMORS), underscoring the importance of incorporating horizontal diffusion terms in local circulation simulations. These findings are crucial for improving wind field simulation accuracy under complex terrain conditions using three-dimensional boundary layer schemes and provide valuable insights for future research.
How to cite: Xu, H., Han, C., and Ma, Y.: Application of Three-Dimensional Boundary Layer Schemes in Wind Field Simulation under Complex Terrain of the Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11626, https://doi.org/10.5194/egusphere-egu25-11626, 2025.
The southern Himalayan slopes are increasingly experiencing dry winters, posing significant challenges to water resources and agriculture. These conditions have intensified forest fires in Nepal, mainly driven by human activities such as unattended campfires, discarded cigarettes, and arson. A warmer and drier climate exacerbates the spread of these fires, causing severe air pollution and accelerating snow and glacier melt due to black carbon deposition in the Himalayas. Recent forest fire events, particularly in 2021 and 2024, were ten times higher than the long-term average, fueled by extended post-monsoon droughts. Climate models (CMIP3, CMIP5, and CMIP6) project worsening winter droughts, leading to an increased frequency and intensity of forest fires throughout the 21st century. Our study, based on observational, remote sensing, and climate model data, highlights climate variability and climate change-induced droughts as primary drivers of these fires. Projections indicate that persistent droughts will elevate wildfire risks and degrade air quality, posing severe threats to public health, ecosystems, and the economy. This presentation will discuss historical trends and future projections of forest fires, emphasizing their impact on regional air quality, as fire smoke can travel hundreds of kilometers.
How to cite: Aryal, D. and Pokharel, B.: Climate Change-Induced Drought and Its Role in Nepal's Forest Fires, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4621, https://doi.org/10.5194/egusphere-egu25-4621, 2025.
78% of the Three River Source Region (TRSR) is covered by grassland, understanding future variations in grassland growth is fundamental to ecological barrier security. Many advanced land surface models have incorporated vegetation growth modules, but rarely have current land surface models considered the differential growth of pasture and toxic weeds, which have quite different roles in altering surface energy and water cycles. To represent the different growth for pasture and toxic weeds, we performed a global parameter sensitivity analysis for the Community Land Model (CLM5) based on the eFAST algorithm and calibrated two sets of parameters representing pasture and toxic weeds growth. The previous overestimation of Leaf Area Index and above ground biomass was largely reduced after the parameter optimization. Then we performed future simulations for four Shared Social-economic Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) during 2015-2100, considering only meteorological impacts and ignoring other future changes (e.g. CO2 or nitrogen deposition). Pasture and toxic weeds biomass (fresh weight) showed a statistically significant increasing trend in all SSPs. This trend was higher for pasture (5.58-22.76 kg·Ha-1·yr-1) than for toxic weeds (2.12-7.44 kg·Ha-1·yr-1), while toxic weeds showed greater interannual variability. Radiation and soil mineral nitrogen became the two main constraints on future grassland greening rather than warming and moisture. The strongest biomass increases in SSP5-8.5 were mainly due to increases in pasture and toxic weeds biomass in the western TRSR. Such spatial differences between indicated that the western TRSR had much greater uncertainties in the future.
How to cite: Lu, Y., Meng, X., Li, J., Liu, X., Wang, L., Deng, M., Yang, Y., Liu, B., and Yu, H.: Parameter optimizations and future projections of pasture and toxic weeds with the Community Land Model (CLM5) over the Three River Source Region, Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2413, https://doi.org/10.5194/egusphere-egu25-2413, 2025.
The Central Himalaya faces significant air pollution challenges, with nearly half of the days each year in Kathmandu Valley surpassing the PM2.5 national air quality guideline of 40 µg/m³. Wildfire smoke, especially during the pre-monsoon season, is a major contributor to these polluted days in the valley and is also a key driver of air pollution in high-altitude regions of the Himalayas. To identify the presence of wildfire smoke in the valley, we utilized multiple datasets, including in-situ observations, Himawari satellite Aerosol Optical Depth (AOD) data, and satellite imagery. Between 2018 and 2023, we identified 114 days that met our criteria for being classified as smoke days during the pre-monsoon season. Due to the lack of in-situ observation data prior to 2018, we utilized PM2.5 data from the Copernicus Atmosphere Monitoring Service (CAMS), MODIS AOD and wildfire data to classify smoke days for earlier years. Using in total of nine variables, we trained a Random Forest Classifier model on the previously categorized dataset, our model performed with outstanding accuracy (0.91), where AOD in nearby regions (~150km) was found to be the most significant parameter, followed by number of wildfires occured in the past three days. In total, 213 days were classified as wildfire smoke days in Kathmandu Valley from 2003 to 2023, with 2021 recording the highest number of smoke days and 2009 with the highest amout of PM2.5 due to the smoke. Additionally, these wildfire smoke days do not folow any trend but were strongly correlated with wildfire occurrences in nearby regions. The Machine Learning model further highlighted the high correlation between wildfire numbers in surrounding areas and the presence of high air pollution in the valley. This research contributes to policymaking on air pollution and enhances preparedness for extreme pollution events in Kathmandu Valley, ultimately helping to protect public health and well-being.
How to cite: Kuikel, S., Sapkota, S., Kuinkel, D., Paudel, H. K., Joshi, K. P., Marahatta, S., Aryal, D., and Pokharel, B.: Prediction Air Polution due to Wildfire in Kathmandu Valley: Remote Sensing and Machine Learning Techniques, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-490, https://doi.org/10.5194/egusphere-egu25-490, 2025.
The Tibetan Plateau region is experiencing increasing runoff and sediment load in its headwater regions driven by the impacts of climate change, such as glacial retreat, permafrost degradation, and alterations in precipitation patterns. However, study on the changes in sediment load in the high-altitude Himalayas region remains challenging due to sparse observation data under the harsh climatic and topographic conditions. Recently, remote sensing has emerged as a promising tool in sediment studies, with several applications in the Himalayas; however, high cloud coverage during the high-flow season often leads to underestimation of sediment load. To address this issue, we introduce a remote-sensing approach to supplement the hydrological model calibration process using a less suspended sediment concentration (SSC) to quantify the long-term sediment transport in the Koshi River Basin (KRB). Landsat 8-9 OLI and the Landsat 4-5 TM images were selected to estimate Landsat-SSC with observed SSC data taken from the Chatara gauging station. Then the SWAT model was calibrated using the Landsat-SSC and validated by applying the monthly observed data from both the Chatara and Mulghat gauging stations. After model calibration and validation, the sediment load was simulated for 42 years (1981–2022). Additionally, the partial least squares-structural equation model (PLS-SEM) was used to quantify the complex relationships of sediment regimes with the potential influencing factors including hydro-climatic conditions, topographic variables, vegetation cover, and soil types. Results show that the surface reflectance of visible band combinations (R+G-B) exhibited the highest Pearson correlation with observed SSC data, allowing a power regression equation to estimate SSC from 1987 to 2022. The statistical analysis demonstrates a strong agreement between SWAT-SSC, Landsat-SSC, and Observed-SSC during calibration and validation. The annual sediment load of KRB at Chatara station is estimated at 75 Million tons (Mt) with a significant contribution during the monsoon season. The basin scale sediment load shows a significant increasing trend (p<0.01), with an average rate of 6.97 Mt/10a, which became more pronounced after 2001. PLS-SEM analysis shows that the above-considered potential influencing factors can explain 72% of the total variations, with a significant impact of hydro-climatic conditions (β=0.86, p<0.01) and vegetation cover (β=-0.56, p<0.05). The increasing sediment load in the KRB is primarily due to the strong influence of hydro-climatic changes. The negative influence of land cover changes highlights the buffering effect of increased vegetation cover on sediment export. Above all, by integrating remote sensing with hydrological modeling, this study applied new methods to estimate sediment loads with limited data and subsequently obtained critical insights into the impact of climatic and environmental changes on sediment transport, offering valuable information for soil conservation planning in the data-scarce Himalayan region.
How to cite: Bishwakarma, K., Xiang, Y., and Zeng, C.: Integration of remote sensing and hydrological modeling to estimate a basin-scale sediment transport in the data-scarce Himalaya region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3134, https://doi.org/10.5194/egusphere-egu25-3134, 2025.
The summer atmospheric heat source (AHS) over the Tibetan Plateau (TP) induces meridional circulations in TP and its surrounding areas. Previous studies mainly focused on the monsoon circulation on the south side of TP, while the formation and maintaining mechanism of meridional circulation on its north side remain unclear. This study compared three calculation methods of the AHS, analyzed spatial-temporal variability of the summer AHS over the TP, and discussed its influence on interannual variability of meridional circulation on the north side of TP based on the two-dimensional decomposition method of atmospheric circulation and sensitivity experiments. The results indicate that in the positive AHS anomalies years, the diabatic heating of condensation latent release in southeastern TP could motivate anomalous ascending motion. Simultaneously, the increased meridional temperature gradient between the middle and high latitudes of East Asia leads to an enhanced southward westerly jet. In this context, the region on the north side of TP, located on the north side of westerly jet entrance, is affected by negative anomalous relative vorticity advection, prevailing anomalous descending motion, which makes the descending branch of meridional circulation significantly presented. Unlike previous studies considered the descending branch of meridional circulation as the compensation for upward flow, the results of LBM model verify the descending branch is mainly influenced by the vorticity advection related to regional scale variability of westerly jet. This study reveals the physical mechanism of meridional circulation on the north side of TP, which offers valuable implications for seasonal forecasting in TP and Northwest China.
How to cite: Luo, H. and Yu, H.: Impact of the summer atmospheric heat source over the Tibetan Plateau on interannual variability of meridional circulation on the north side of Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2423, https://doi.org/10.5194/egusphere-egu25-2423, 2025.
Lake thermal stratification is of great importance to hydrodynamics and transport of nutrients, oxygen, and primary production, which influence limnology and local climate. The thermal regime of the lakes over Tibetan Plateau (TP) was summarized as follow. During summer, solar radiation unevenly heats the water column in the vertical direction, resulting in a stratified thermal structure. The stratification dissipates in October, after which time a more uniform vertical distribution of temperature is observed. This occurs because the increased temperature gradient between the air and lake surface, combined with strong winds, drives considerable energy transfer from the lakes to the overlying air, and leads to a rapid decrease in surface water temperature. This result increases in density of the upper layers and then drives vertical convection that deepens the mixed layer. When the lakes have been completely frozen, the vertical water circulation stops; weak thermal stratification then develops and persists during winter. However, lake water near the surface warms rapidly, and rest water layer does not change much when lakes are covered with ice. When the lake ice disappears, wind-driven turbulence develops and promotes lake vertical mixing. Due to sparse observation, the lake modeling was an alternative method to simulate the seasonal lake thermal change induced by local climate change. Using lake model, the seasonal variation and magnitude of water temperature at different layers were reproduced fundamentally. The interaction heat flux and water exchange with overlying air also were simulated with reasonable error. Both the simulation and observation have shown that the thermal characteristic and ice phenology has altered: warming water and shorter ice duration, impacted by climate change. Meanwhile, the future projection of thermal response of lakes over TP to climate change shows that remarkable water temperature increase and winter ice loss which indicates less mixing frequent and shifting mixing regime. The Lake mixing events can channel the epilimnion and hypolimnion and release large amounts of potent greenhouse gases into the upper surface layer and the atmosphere in autumn, making lakes generally being considered as a weak net carbon source. The epilimnion depth show significant implications on the algal distribution, photosynthesis rates and establishing food web basis. Thus, the seasonal variations of thermal stratification and mixing in lakes can influence the aerobic life, prevent anoxia and impact on local climate and it is one of the most important factors in limnology and climate change.
How to cite: La, Z., Ma, X., Zhou, X., Yi, W., and Gan, H.: Lake thermal dynamics and its potential impact on lake ecological system on the Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8216, https://doi.org/10.5194/egusphere-egu25-8216, 2025.
Abstract. The Qinghai-Xizang Plateau has owned a large number of various types of wetlands, which serve as major pastures for regional animal husbandry and water restoration. Among, Mitika Wetland (MW) is located in Lhari county in Nagqu city, southwest China's Xizang Autonomous Region, with an average elevation of 4,900 m.a.s.l.. It is known as the Mitika Wetland National Nature Reserve (MWNNR) in China and it is the first wetland in Xizang that has been included on the List of Wetlands of International Importance. MWNNR is also known as the headwater region of Lhasa River, the “mother river” of people in Lhasa city. Study on its current status of soil fertility and geochemical characterization is therefore crucial for better understanding of its future vagaries under the global changes.In this study, analysis of 10 soil physiochemical parameters and 37 elements were carried out for the evaluation of topsoil fertility and geochemical features of the MW. The non-parametric test results indicated that the contents of soil organic matter, total organic carbon (TOC), cation exchange capacity (CEC), soil moisture, soil bulk density and soil salinity were in large extent related to the soil type. In contrast, pH, contents of available potassium, available phosphorus, ammonia nitrogen were regardless with soil type. Comprehensive soil fertility coefficient (F) among the different soil types studied in the wetland was as following: alpine meadow soils (1.72)＞alpine shrub meadow soils (1.66)＝frigid desert soils (1.66)＞bog soils (1.56)＞skeletal soils (1.43). Except the alpine meadow soil belonged to fertility grade, the other types belonged to the general grade, as this is the common state on the Plateau. Despite the high elevation and hash climate, nevertheless, soil fertility level in MW is comparable to that of cultivated land or artificial afforestation areas in the lower altitude (<3000 m.a.s.l.) regions of Xizang. Combined results from comparison with reginal background value and source identification using multivariable analysis showed that the contents of most studied soil elements were equivalent to the background values, and their distribution have been greatly affected by the geological background. In general, this study shows that the soil fertility of the alpine wetland located in the remote northeastern Xizang with a high elevation, surprisingly, have an adequate supply of soil nutrients to the pastures and, in a large extent, still remain chemically undisturbed under global change and human activities. Obviously, the wetland has played a key role in ecologically secure of the Lhasa River catchments.
Keywords: Alpine Wetland, Ecologically Secure, Element’s background value, Source Identification, Multivariable Analysis
How to cite: Huang, X., Chen, H., and Ciren, Z.: Current status of soil fertility and geochemical characteristics of a typical alpine wetland in Xizang, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11158, https://doi.org/10.5194/egusphere-egu25-11158, 2025.
The Tibetan Plateau and surroundings, commonly referred to as the Third Pole region, has the largest ice store outside the Arctic and Antarctic regions. Glacial lakes in the Third Pole region are expanding rapidly as glaciers thin and retreat. The Landsat satellite series is the most popular for mapping glacial lakes, benefiting from long term archived data and suitable spatial resolution (30m since ~1990). However, the homogeneous mapping of high-quality, large-scale, and multi temporal glacial lake inventories using Landsat imagery relies heavily on visual inspection and manual editing due to mountain shadows, wet ice, frozen lakes, and snow cover on lake boundaries, which is time consuming and labour-intensive. Deep learning methods have been applied to glacial lake extraction in the Third Pole and other regions, yet these methods are either concentrated on small test sites without large-scale applications or in polar regions. In this study, several classical deep convolutional neural networks were evaluated, and the DeepLabv3+ with Mobilenetv3 backbone performed best, with a high accuracy of mean intersection over union (mIoU) of 94.8 % and a low loss error of 0.4 %. The proposed method demonstrated robustness in challenging conditions such as mountain shadows, frozen or partially frozen lakes, wet ice and river contact, all without requiring extensive manual correction. Compared with manual delineation, the model’s prediction has a precision rate of 86 %, recall rate of 85 %, and F1-score of 85 %. The area extracted by the model shows a strong correlation with the manual delineation (r2 = 0.97, slope = 0.94) and a high intersection over union (IoU > 0.8) of the predicted areas. A test of large-scale glacial lake mapping based on the developed automated model in 2020 across the Third Pole region shows the robust performance with 29,429 glacial lakes larger than 0.0054 km2 with a total area of ~1779.9 km2 (including non-glacier-fed lakes). The model trained in this study can be fine-tuned for large-scale mapping of glacial lakes in other mountain regions worldwide.
How to cite: Tang, Q., Zhang, G., Yao, T., Wieland, M., Liu, L., and Kaushik, S.: Automatic extraction of glacial lakes from Landsat imagery using deep learning across the Third Pole region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1927, https://doi.org/10.5194/egusphere-egu25-1927, 2025.
Containing elevated topography, the Tibetan Plateau (TP) has significant thermodynamic effects for regional environment and climate change, where understanding energy and water exchange processes (EWEP) is an important prerequisite. However, estimation of the exact spatiotemporal variability of the land-atmosphere energy and water exchange over heterogeneous landscape of the TP remains a big challenge for scientific community. Based on the observation, remote sensing, and numerical simulation, the major advances on EWEP over the past 25 years are systematically summarized in this work. All these results advanced the understanding of different aspects of EWEP over the TP by using in situ measurements, multisource satellite data and numerical modeling. Future studies are recommended to focus on the optimization of the current three[1]dimensional comprehensive observation system, the development of applicable parameterization schemes and the investigation of EWEP on weather and climate changes over the TP and surrounding regions.
How to cite: Ma, Y.: Comprehensive study of energy and water exchange over the Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2693, https://doi.org/10.5194/egusphere-egu25-2693, 2025.
Understanding land-atmosphere (LA) interactions through coordinated, multidisciplinary, and multiscale observations is crucial for addressing global challenges such as water resource management, land-use planning, climate change, and ecosystem preservation. In this study, we introduce a comprehensive observation and research platform for LA water, heat, and CO₂ flux exchange over the TP and provide initial insights into the spatial and temporal variations of meteorological conditions, liquid precipitation, and turbulent fluxes over the Tibetan Plateau. Diurnal precipitation patterns reveal three types: peak at night, peak during the day, and bimodal peaks. While liquid precipitation can distinguish between water-limited and energy-limited regions, where soil moisture—both from surface and deeper layers—also plays a key role in surface evapotransporation. Net ecosystem exchange (NEE) fluxes are near zero at bare ground stations, show significant carbon release in forested areas, and function as carbon sinks in most alpine meadows and alpine steppe sites.
How to cite: Wang, B., Ma, Y., Ma, W., Chen, X., Han, C., and Xie, Z.: The eddy covariance based spatial and temporal land-atmosphere turbulent heat and CO2 flux over the Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2711, https://doi.org/10.5194/egusphere-egu25-2711, 2025.
Applying observed surface parameters and atmospheric vertical profiles, our study simulated and analyzed the mechanism of shallow convective cloud triggering and deep moist convection development in the lake region of the Tibetan Plateau. The research found that lake breeze circulation not only aids in triggering convection but also has the ability to horizontally transport water vapor, creating favorable conditions for the transition from shallow cumulus convection to deep moist convection. These results suggested that future studies on energy and water cycles in the Tibetan Plateau should prioritize the lake regions. Lakes serve not only as a “water supply source” for the water cycle in the Tibetan Plateau but also have a unique mesoscale system—lake breeze circulation, which provides positive feedback for the development of convection, as well as for water and heat exchange between the atmosphere and the underlying surface. Additionally, previous studies indicated that the area of lakes in the Tibetan Plateau has increased in the past, and existing studies predict that this trend will continue. The findings of this paper indicated that the increase in lake area is related to an increase in precipitation, providing important references for research on the water cycle in the Tibetan Plateau under climate change.
How to cite: Zhang, Y. and Han, C.: Large eddy simulation study on the mechanism of convection initiation in the lake region of the Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11141, https://doi.org/10.5194/egusphere-egu25-11141, 2025.
The distribution of water resources in sub-basins across the Western Tibetan Plateau (WTP) is of critical importance due to not only ecological vulnerability resulting from the extremely arid climatology but also the political sensitivities surrounding the international rivers. In this study, we utilize an advanced water vapor tracer (WVT) embedded in the widely used regional climate model – Weather and Research Forecast (WRF), to quantify moisture contributions from four main sources towards precipitation over the WTP region. We also analyze influences on other sub-basins in the TP for comparison purposes. We examine how changes in sea surface temperature (SST) during 2010s compared to 1980s have influenced precipitation patterns and moisture contributions over recent decades. Our findings indicate that terrestrial moisture sources contribute more than oceanic sources towards the endorheic TP region. Recycling processes originating from highlands area are revealed to play a greater role in contributing moisture over WTP compared to those from lowlands areas. Furthermore, our results demonstrate stronger agreements between wetting distribution patterns and distributions of liquid/solid hydrometeors rather than water vapor distribution itself, highlighting condensation/freezing as critical factors. Notably, we observe different responses within Amu Dayra basin compared to the main WTP when subjected to SST changes. This study focuses on delineating distinct roles of terrestrial and oceanic moisture sources in driving precipitation changes over WTP, while specifically emphasizing condensation process’ contribution to inner TP’s precipitation and highlighting moisture transport form oceans’ influence on precipitation patterns over Amu Dayra basin.
How to cite: Gao, Y.: The influence of moisture on precipitation patterns across the Western Tibetan Plateau , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1862, https://doi.org/10.5194/egusphere-egu25-1862, 2025.
To explore the characteristics of evapotranspiration (ET) and its main influencing factors at typical stations across different regions of the Tibetan Plateau, and to deepen the understanding of land-atmosphere interactions and eco-hydrological processes in the region, this study selected four representative stations: Muztagh, Naqu, QOMS, and SETS. Based on long-term observational data and satellite remote sensing, we analyzed the actual evapotranspiration at each station across different temporal scales, along with its correlation with meteorological factors. The results are summarized as follows:(1) Annual Variation: The annual evapotranspiration at Muztagh, Naqu, and SETS showed an increasing trend, while a decreasing trend was observed at QOMS. At Muztagh, annual evapotranspiration was significantly correlated with net radiation, while at SETS, it was significantly positively correlated with temperature. No significant correlation was found between the annual evapotranspiration and any meteorological factor at QOMS or Naqu, suggesting that the changes may be influenced by multiple factors. (2) Monthly Variation: Monthly evapotranspiration at all stations exhibited a unimodal pattern. During the monsoon period, evapotranspiration accounted for 71.45% of the annual total at QOMS, the highest among the four stations, followed by Naqu (66.49%), Muztagh (60.81%), and SETS (55.34%). The factors influencing evapotranspiration varied by station: during the monsoon, Muztagh was influenced by soil moisture and net radiation; Naqu was mainly influenced by soil moisture and temperature; QOMS was affected by precipitation and soil moisture, with precipitation having a stronger influence; and SETS was controlled by net radiation. (3) Diurnal Variation: Diurnal evapotranspiration at all stations exhibited an inverted U-shaped curve during different periods. During the monsoon, the peak diurnal evapotranspiration followed the order: Naqu > SETS > Muztagh > QOMS. In contrast, during the non-monsoon period, the sequence was SETS > Naqu > Muztagh > QOMS. Path analysis revealed that the dominant factors influencing diurnal evapotranspiration varied across stations: at Muztagh, evapotranspiration was primarily influenced by net radiation and soil moisture. At Naqu and QOMS, soil moisture was the dominant factor, while at SETS, temperature was the primary influence, followed by net radiation.
How to cite: Chen, T.: Analysis of Evapotranspiration Variation Characteristics and Influencing Factors in Different Regions of the Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7704, https://doi.org/10.5194/egusphere-egu25-7704, 2025.
Nam Co Lake, located in the Tibet Plateau region, is the highest and second-largest enclosed salt water lake in China, and is a representative area for the study of long-range atmospheric transport (LRAT) and climate change of perfluoroalkyl and polyfluoroalkyl substances (PFASs). We analyzed the causes of spatial heterogeneity of 18 PFASs in 17 lake samples, 7 glacial runoff samples, 8 non-glacial runoff samples and 9 sediment samples in or around the Nam Co Lake in 2023. The results showed that the distribution of PFASs in various environmental media around Nam Co Lake can be influenced by glacial melting, salinity, pH, carbon chain length and human activities etc. Due to the melting of glaciers caused by global warming, PFASs deposited in the glaciers over the years flowed into the runoff in large quantities through the meltwater, making the PFAS concentrations in the runoff higher than those in the water of Nam Co Lake. The concentrations of short-chain PFASs in lake water were significantly negatively correlated with pH, possibly because the stronger alkalinity can change the structure and soil chemistry of PFASs and thus reduce their concentration. In contrast to the lake water, there is no significant correlation relationship between the concentration of PFASs in the runoff and the salinity and pH, so the influencing factors of the runoff concentration may be more complex compared to the closed Nam Co Lake, affected by human activities and other factors. The short-chain and long-chain PFASs accounted for the largest and the smallest proportion for both runoff and lake water samples, respectively, while the opposite for sediment samples, indicating that the long-chain PFASs with better hydrophobicity could be easily distributed to sediments. Considering for the irreversible accumulation and aquatic ecotoxicity, the concentrations and partition coefficient of TFA in the water and sediment of Nam Co Lake on the Tibet Plateau were firstly detected and analyzed. The results showed that TFA was the substance with the highest concentration, and the concentration of TFA in lake water, sediment, glacial runoff and non-glacial runoff accounted for 32.09%, 34.39% of ∑PFAS, respectively. Therefore, it was necessary to continuously track the concentration and environmental risk of TFA.
How to cite: Peng, L., Wu, J., Yu, Y., Ma, J., Wang, T., Zhuang, Y., and Liu, Z.: Causes of spatial heterogeneity of PFASs in the Nam Co Lake and surrounding runoff on the Qinghai Tibet Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3668, https://doi.org/10.5194/egusphere-egu25-3668, 2025.
The Asian monsoon affects the natural environment pattern in China, and its origin and evolution have been a debated issue in paleoclimatology. Recent studies indicate that the Asian monsoon reached the subtropical zone at least ~ 41 Ma and expanded to the central Tibetan Plateau during the Late Oligocene, but more geological evidence is still required to confirm its spatial evolution. The well-developed Late Oligocene paleosols in the Lunpola Basin, central TP, provide excellent material to address the above issue. In this paper, various climatic proxy indicators suggest that the late Oligocene LPL paleosols were forest cinnamon soils, as shown by the significant compound Bt and Bk horizons, abundant clay coating and carbonate nodules, and diagnostic clay chemical composition in Bt horizons. High CIA value, Rb/Sr ratio, and high content of illite/smectite mixed layer mineral show that these paleosols experienced intense weathering and leaching pedogenesis. Furthermore, the mean annual temperature and mean annual precipitation of the Late Oligocene LPL Basin were 10.4~14.8 ℃ and 615~1128 mm estimated by the empirical formulas, respectively, which are comparable to the monsoonal climate parameter of Chinese modern cinnamon soils. So the development of these paleosols in the LPL Basin indicate that the Asian monsoon has reached the central TP at least during the Late Oligocene, providing important independent evidence for the study of the evolution of the Asian monsoon.
How to cite: Guo, Z., Ming, Q., Kang, G., Chen, J., Wang, G., Ma, X., Wei, Z., Zhang, X., Huang, X., and Wang, Y.: Late Oligocene monsoonal climate in the Lunpola Basin, central Tibetan Plateau: evidence from paleosol records, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14064, https://doi.org/10.5194/egusphere-egu25-14064, 2025.
Glaciers are essential for understanding environmental changes, particularly on the vulnerable Tibetan Plateau with its vast low-latitude glacier coverage. Understanding glacial microbiomes and viruses is vital for evaluating ecosystem functions and ecological modeling, especially for the Tibetan Plateau's mountain glaciers, which support approximately 20% of the global population.
From sequencing 85 metagenomes and 883 cultured isolates from 21 Tibetan glaciers, we've developed the Tibetan Glacier Genome and Gene (TG2G) catalog, which represent 968 candidate species spanning 30 phyla. The catalog also contains over 25 million non-redundant protein-encoding genes, the utility of which is demonstrated by the exploration of secondary metabolite biosynthetic potentials, virulence factor identification and global glacier metagenome comparison.
Additionally, we present the Supraglacial Virus Genome (SgVG) catalog, expanding the genomic inventory of 10,840 DNA-virus species from 38 mountain and polar glaciers. These viruses, mainly found in snow, ice, meltwater, and cryoconite, have habitat-specificity and low public health risks. They significantly influence supraglacial microbial communities, with cryoconite hosting the highest viral activity.
How to cite: Liu, Y.: Genomic Insights into Glacial Microbiomes and Viral on the Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1864, https://doi.org/10.5194/egusphere-egu25-1864, 2025.
Mountainous areas experience significant variations in temperature, humidity, and vegetation over short distances, thus mountain ecosystems are particularly sensitive to climate change. The Hengduan Mountains, located to east of the Tibetan Plateau, are characterized by a diverse terrain that includes plateau surfaces, alpines and lake basins. In this study, we present two pollen records from two cores in the Hengduan Mountains. Core YL from Lake Tianchi spans the last 23 ka, while core XMLT-1 from Lake Ximenlongtan covers the last 9.4 ka.
Around Lake Tianchi, the Tsuga dumosa forest zone migrated at least 650 m upward from 23 to ~7 ka, indicating a gradual increase in mean annual temperature exceeding 3.9 °C. In response to this warming, there was a successive colonization of different tree communities: grass and deciduous broadleaved trees dominated from 23 to 15 ka; warm deciduous broadleaved trees prevailed from 15 to 8 ka; and finally, warm coniferous trees (primarily Tsuga dumosa) and subtropical evergreen broadleaved trees dominated from 10 to 5 ka. After 5 ka, there was an increase in deciduous trees and grass, while evergreen trees decreased. Around the Lake Ximenlongtan area, tropical evergreen broadleaved trees dominated from 9.4 to 5 ka. However, after 5 ka, subtropical evergreen trees and grass increased at the expense of tropical evergreen trees.
At both sites, a significant shift in vegetation took place ~5 ka. The concurrent decline of subtropical evergreen trees around Lake Tianchi and tropical evergreen trees around Lake XMLT suggest a notable cooling event in western Yunnan, highlighting a trend toward decreasing monsoon intensity.
How to cite: Jiang, W., Yang, X., and Huang, X.: Vegetation changes in the Hengduan Mountains, China since the Last Glacial Maximum, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1257, https://doi.org/10.5194/egusphere-egu25-1257, 2025.
Climate change has profoundly altered the vegetation and soil moisture dynamics and intensified land-atmosphere interactions, particularly in climate sensitive regions. However, exactly how vegetation affects soil moisture responses to climate change and its regional differences remains unclear. In this paper, we investigated changes in temperature, precipitation patterns, vegetation, and soil moisture (SM), and estimated the impact of vegetation greening on soil moisture sensitivity to temperature and precipitation from 1982 to 2060 under various Shared Socioeconomic Pathways (SSPs). The results show that increasing trends of light precipitation under all SSPs are greater than that in the historical period, while changes in medium and extreme precipitation are weaker, which leading to smaller changes in SM relative to precipitation under all SSPs. Vegetation greening induced by warming and increased precipitation on the TP, reduces the negative contribution of temperature to SM and the positive contribution of precipitation on SM in semi-arid and arid regions, where the leaf area index (LAI) exhibits a positive correlation with SM. Additionally, the impact of vegetation greening on shallow SM responses to temperature intensifies during 2019~2060 under all SSPs compared to 1982~2018. These findings highlight the critical need for integrated land management strategies to address the compounded effects of vegetation-soil feedbacks under climate change.
How to cite: Deng, M., Meng, X., and Oliver, R.: Climate change-induced vegetation greening reduces soil moisture sensitivity on the Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10079, https://doi.org/10.5194/egusphere-egu25-10079, 2025.
The analysis of the Tibetan Plateau (TP) by seasonal classification using EOF reveals the existence of a north-south temperature dipole phenomenon in spring, autumn and winter, with spring being the most evident. The spring temperature EOF indicates that there is a thermal dipole between the TP and its high-latitude regions, as confirmed by the correlation analysis curve. This finding suggests the presence of an inverse correlation of temperature between the surface of the TP and its mid and high latitude regions. In this study, we used the ERA5 reanalysis data to preliminary understand the thermodynamic forces of the TP impact the spring temperature dipole at middle and high latitudes. When the Arctic Oscillation index (AOI) is negative, the pressure in the Arctic is high. After the enhanced cold air is transported to the mid-latitude region, it is deposited around 60°N due to the topographic blocking effect of the Tibetan Plateau, and the mid-latitude region is cooled. The decrease of temperature gradient between the northern and mid-latitudes leads to the weakening of Ferrel cell and the weakening of cold air transport to the plateau, warming the plateau. The results will help us to play the role of "climate indicator" on the Tibetan Plateau, and provide certain reference for climate prediction, water resources management, ecological protection, disaster warning and other aspects.
How to cite: Lou, X. and Hu, Z.: The Influence of Mechanical and Thermal Forcing by the Tibetan Plateau on the Spring Temperature Dipole in the Middle and High Latitudes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7719, https://doi.org/10.5194/egusphere-egu25-7719, 2025.
Wind speed spectra analysis is of great importance for understanding boundary layer turbulence characteristics, atmospheric numerical model development, and wind energy assessment. 15-year time series of near-surface horizontal wind data from the national Observation and Research Station for Qomolongma Special Atmospheric Processes and Environmental Changes (QOMS) on the north slope of Mt. Everest has been used to investigate the full-scale wind spectrum in the frequency range from about 10 yr-1 to 5 Hz. The annual average wind speed showed almost no detectable trend from 2006 to 2018 at the QOMS station. Three peaks were identified in the full-scale spectra at the frequencies of 1 yr-1, 1 day-1, and 12 hr-1, respectively. The 12 hr-1 peak is evident in spring and summer but disappears in winter, indicating the seasonal differences in local circulations at the QOMS station. The spectral density was the highest on the low-frequency side of the diurnal peak and in the microscale frequency range (f ≥ 1×10-3 Hz) in winter, indicating frequent synoptic weather events and vigorous turbulent intensity generated by shear due to strong wind during winter. An obvious spectral gap around the frequency of 4.5×10-4 Hz was observed in the composite seasonal and daily spectrum in winter, while the spectral gap disappeared in summer. The linear composition of microscale and mesoscale wind spectra also held, and the gap region of the horizontal wind spectrum was modeled very well at the QOMS site.
How to cite: Han, C., Ma, Y., and Ma, W.: Full-scale spectra of 15-year time series of near-surface horizontal wind speed on the north slope of Mt. Everest, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3047, https://doi.org/10.5194/egusphere-egu25-3047, 2025.
The Tibetan Plateau summer monsoon is an important component of the Asian monsoon system, significantly influencing the energy and moisture cycles in the plateau and its surrounding regions. This study uses JRA-55 monthly reanalysis data from 1980 to 2020 and GPCC monthly precipitation data, combined with the Tibetan Plateau Monsoon Index. This paper focuses on the impact of the summer monsoon over theTibetan Plateau on water transport, such as precipitation, atmospheric circulation, and water budget. The results show that: (1) When the Tibetan Plateau summer monsoon is strong (weak), precipitation in the central and eastern parts of the plateau increases (decreases). (2) From the perspective of water vapor transport, when the summer monsoon over the plateau is stronger, there is an anomalous anticyclonic circulation over central India, an anomalous westerly airflow to the south of the plateau, and the water vapor transport over the plateau is primarily dominated by the westerly water vapor transport channel.(3) Analysed in terms of moisture budget, when the Tibetan Plateau summer monsoon is strong (weak), moisture inflow at the southern and western boundaries of the plateau increases (decreases), while moisture inflow at the northern boundary decreases (increases), resulting in an increase (decrease) in regional net moisture budget. (4) The impact of the Tibetan Plateau summer monsoon on moisture convergence/divergence is mainly driven by the contribution of the wind’s dynamic component, while the thermal component from moisture advection is relatively small.
How to cite: Zhang, H. and Hu, Z.: The characteristics of water vapor transport during the Tibetan Plateau summer monsoon in 1980-2020, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2386, https://doi.org/10.5194/egusphere-egu25-2386, 2025.
The open-path eddy covariance (OPEC) system is widely employed for direct measurement of CO₂ exchange between terrestrial ecosystems and the atmosphere, offering high accuracy in CO₂ observations. However, the performance of OPEC in cold environments, particularly in alpine regions, remains a key topic of research. This study, based on in-situ observations near Lhasa in the central-southern Tibetan Plateau, China (altitude: 3560.8 m), compares CO₂ mixing ratio (Xc) measurements obtained from OPEC and closed-path eddy covariance (CPEC) systems during both cold and warm seasons, with CPEC serving as the benchmark. Our results show that OPEC significantly underestimates Xc during the winter, with average discrepancies of 18.33 ppm and 27.75 ppm across two distinct observational periods. In contrast, during the warm season, Xc measurements from both systems are highly consistent. Further analysis indicates that this underestimation is primarily due to temperature-sensitive biases in the pressure measurements of the OPEC system. To mitigate this issue, we developed a semi-empirical correction model based on air temperature and Xc to adjust the OPEC data. After applying the correction, the adjusted OPEC Xc values align closely with CPEC measurements (y = x - 0.05 and y = x, RMSE = 1.67 and 1.02, at operational temperatures of 30°C and 5°C, respectively). Our findings highlight the importance of correcting OPEC-measured Xc in cold seasons to improve the accuracy of CO₂ concentration measurements in eddy covariance systems.
How to cite: Li, W. and Wang, B.: Analyzer temperature sensitivity leads to an underestimation of CO2 by the open-path eddy covariance system in winter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5888, https://doi.org/10.5194/egusphere-egu25-5888, 2025.
Sea surface temperatures (SST) in the Atlantic and Pacific Oceans and surface sensible heat flux (SH) over Asian plateaus, including the Tibetan Plateau (TP), Iranian Plateau (IP), and Mongolian Plateau (MP), underwent abrupt shifts in the late 1990s, significantly influencing China’s rainfall variability. A Statistical method is used to examined the relative contributions of these two factors, revealing that land conditions (plateau SH) contribute slightly more, but are nearly equal to the contributions from ocean conditions (SST). The results suggest anomalous SH heating over the MP leads to significant atmospheric warming, while the weakened SH over the TP and strengthened SH over the IP alter the local atmospheric circulation (i.e. South Asian High). These thermal forcings trigger an anomalous anticyclone over the MP and northeastern China, strengthen the teleconnection pattern across Eurasia, and simultaneously modulate the westerlies and the Asian summer monsoon systems, thereby influencing summer precipitation in China. Furthermore, we use the Community Earth System Model to further verify these results. This study provides new insights into the role of land forcing and ocean forcing on the interdecadal variability of China’s summer rainfall and offers important evidence for understanding the mechanisms through which external climate forcings affect China’s precipitation patterns.
How to cite: Yao, N., Ma, Y., and Wang, B.: The relative contributions of Sea surface temperature and Plateau surface sensible heat flux to China’s interdecadal summer precipitation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19365, https://doi.org/10.5194/egusphere-egu25-19365, 2025.
In the year 2023, much of the world experienced record-breaking extreme heat and drought following the Triple-Dip La Niña. However, the Tibetan Plateau witnessed anomalous wetting but milder cooling, and the impact of these changes on the dynamics of permafrost-affected lake areas remains unclear. Here, we integrated lake maps from 2020 to 2023 and permafrost distribution to analyze the spatiotemporal heterogeneity of permafrost-affected lakes over Tibetan Plateau. The results showed that the area of permafrost-affected lakes increased by 2.1 % year-1 (1245.89 km2) from 2020 to 2023 over Tibetan Plateau, representing a 25% higher growth rate compared to the period from 1990 to 2020. Moreover, the expansion of permafrost-affected lakes exhibited strong spatial heterogeneity. Specifically, the 95% (1159.48 km2) of the total increase area occurred in endorheic basins with larger permafrost coverage and increased net precipitation (precipitation minus evaporation). In contrast, the exorheic basins with fragmented permafrost coverage instead exhibited a markable slowdown expansion by only 0.98% year-1, due to the decrease in net precipitation. These findings highlighted the compounded effects of extreme precipitation events and permafrost degradation on lake expansion over Tibetan Plateau.
How to cite: Ji, X., Yu, X., Zhao, Y., and Wang, T.: Amplified Expansion of Permafrost-Affected Lakes on Tibetan Plateau impacted by the Triple-Dip La Niña Event (2020–2023), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14402, https://doi.org/10.5194/egusphere-egu25-14402, 2025.
