HS6.10

The exchange of heat and water vapor between land surface and atmosphere over the Third Pole region (Tibetan Plateau and nearby surrounding region) plays an important role in Asian monsoon, westerlies and the northern hemisphere weather and climate systems. Supported by various agencies in the People’s Republic of China, a Third Pole Environment (TPE) Integrated Three-dimensional Observation and research Platform (TPEITORP) is now implementing over the Third Pole region. The background of the establishment of the TPEITORP, the establishing and monitoring plan of long-term scale (5-10 years) of it will be shown firstly. Then the preliminary observational analysis results, such as the characteristics of land surface energy fluxes partitioning and the turbulent characteristics will also been shown in this study. Then, the parameterization methodology based on satellite data and the atmospheric boundary layer (ABL) observations has been proposed and tested for deriving regional distribution of net radiation flux, soil heat flux, sensible heat flux, latent heat flux and evapotranspiration (ET)and their variation trends over the heterogeneous landscape of the Tibetan Plateau (TP) area. To validate the proposed methodology, the ground measured net radiation flux, soil heat flux, sensible heat flux, latent heat flux and ET of the TPEORP are compared to the derived values. The results showed that the derived land surface heat fluxes over the study areas are in good accordance with the land surface status. These parameters show a wide range due to the strong contrast of surface feature. And the estimated land surface heat fluxes are in good agreement with ground measurements, and all the absolute percent difference in less than 10% in the validation sites. It is therefore conclude that the proposed methodology is successful for the retrieval of land surface heat fluxes and ET over heterogeneous landscape of the TP area. Further improvement of the methodology and its applying field over the whole Third Pole region and Pan-Third Pole region were also discussed.

How to cite: Ma, Y.: Land-atmospheric interactions over heterogeneous landscapes of the Third Pole Region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1059, https://doi.org/10.5194/egusphere-egu22-1059, 2022.

The Upper Blue Nile Basin (UBNB) in Ethiopia has a huge hydropower development potential and it covers a considerable amount of the present hydropower consumptions in the country. However, as hydropower is basically rainfall-dependent, its future sustainable utilization under climate change is highly uncertain. As a result, it is critical to identify the amount of wind energy that can be harnessed in the area since wind is a good substitute for hydropower. Nonetheless, wind energy suitability studies and potential estimations are rarely researched in the UBNB. The objective of this study is, therefore, to investigate wind farm suitability based on multi-criteria decision method using Geographic Information System (GIS) and to determine the energy potentials of those suitable areas in UBNB. Wind speed, slope, land use/land cover, distance from grids, roads, urban areas, and protected areas were considered to identify suitable wind farm sites. The relative weights of these factors were calculated and overlaid by the principle of pairwise comparison in the context of the Analytic Hierarchy Process. From the total area it was found that 1498.69 km² was highly suitable. The suggested highly suitable areas for wind farm sites fall in the northeastern part of the study area. For wind power potential investigation, wind speed data of ten sites with 15 min intervals of four years (2017-2020) were accessed from National Meteorology Agency (NMA). And it was statistically analyzed using statistical methods and software like MS-Excel and MATLAB programs. The best Weibull parameters estimator was identified based on the statistical test results for each station. From the wind power density analysis using 15-minute interval wind speed, the highest wind power density was recorded in Wogeltena followed by Gatira. Finally, the power density was higher during dry and short rainy season and can be said that wind is a good complementary to hydropower. In conclusion, most of the wind speed data in this study were not enough for wind energy potential estimations at large scales. This may be because the meteorological stations in the study area may not be located at ideal places for wind energy potential estimations. Thus, different wind speed measuring tools (i.e. taller wind mast) are suggested for additional wind energy potential investigations. Relatively, the northeastern parts of the study area are the most promising sites discovered in this study. Hence, these areas might be regarded as feasible for various wind energy applications (i.e. grid-connected and stand-alone).

How to cite: Tegegne, E. B., Berhanu, Y., and Wang, B.: Suitability Analysis for Wind Farm Establishment and Wind Energy Potential Investigation: The Case of Upper Blue Nile River Basin, Ethiopia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10679, https://doi.org/10.5194/egusphere-egu22-10679, 2022.

The source region of the Yellow River (SRYR) is located in the northeastern of the Tibetan Plateau and is known as the “water tower” of China because it contains 48 lakes. Daytime lake breezes are proved by ERA-Interim reanalysis data in the SRYR. We use the Large Eddy Model to depict the effect of the circulations induced by surface anomaly heating (patches) on the boundary-layer turbulence. A set of 1D tests of strip-like surface heat flux distribution are carried out, which based on observations in the Ngoring Lake basin in the summer of 2012. The simulations show that for the cases without background wind, patch-induced circulations (SCs) promote the growth of convective boundary layer (CBL), enhance the turbulent kinetic energy (TKE), and then modify the spatial distribution of TKE. Based on phase-averaged analysis, which separates the attribution from the SCs and the background turbulence, the SCs contribute no more than 10% to the vertical turbulent intensity, but their contributions to the heat flux can be up to 80%. The thermal internal boundary layer reduces the wind speed and forms the stable stratification, which produces the obvious change of turbulent momentum flux and heat flux over the heterogeneous surfaces. The increased downdrafts, which mainly occur over the lake patches, carry more warm, dry air down from the free atmosphere. The background wind inhibits the SCs and the development of the CBL; it also weakens the patch-induced turbulent intensity, heat flux, and convective intensity.

How to cite: Zhang, Y., Huang, Q., and Ma, Y.: Large eddy simulation of boundary-layer turbulence over heterogeneous underlying surfaces in the northeastern Tibetan Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1580, https://doi.org/10.5194/egusphere-egu22-1580, 2022.

The Tibetan Plateau (TP) is the highest plateau in the world and has complex topography. On the TP, seasonal snow cover is widespread in different topographic areas, but the influence of topography on snow cover simulations is often ignored in most land surface models. In this study, the relationships among the snow cover fraction (SCF) and complex topography are investigated over the TP based on satellite observations. The standard deviation of topography is used as an index to describe the topographic complexity. We conduct 12 numerical experiments using the Simplified Simple Biosphere Model version 3 (SSiB3) to investigate the influence of topography on the snow cover simulations. Our results show that ignoring topography leads to significant SCF simulation biases. By adding a topographic factor to the original scheme, the SCF simulations are greatly improved. Compared with the simulation results of the default SCF scheme, the annual mean SCF bias at location at CMA stations is reduced from 3.833% to -0.097% by adding a topographic factor. The improved SCF simulations further lead to reduced biases in winter surface albedo and land surface temperature simulations. Compared with in situ observations, the winter surface albedo bias over the TP is reduced from 0.02 to 0.007 compared with GLASS albedo data, and the winter land surface temperature bias is reduced from -3.43 K to -3.04 K. This study highlights the importance of the topographic effect in simulating snow and energy exchanges between the land and atmosphere over the TP, and it can contribute to reducing the “cold bias” in winter climate simulations over the TP.

How to cite: Miao, X., Guo, W., Xue, Y., and Sun, S.: Influence of topography on Tibetan Plateau snow cover simulations in land surface modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1957, https://doi.org/10.5194/egusphere-egu22-1957, 2022.

The riverine runoff and sediment are essential carriers for nutrients and pollutants delivery and are considered as important indicators of land degradation and environmental changes. With growing interest in environmental changes over the Tibetan Plateau, this study investigated mean annual runoff depth and sediment yield from eight headwater catchments in relation to dominant factors such as annual precipitation, air temperature, and glacier area ratio, etc. Results show that runoff depth (Q) is positively correlated with both precipitation (P) and temperature (T), indicating combined water supply from rainfall and meltwater, increase of which may exceed the evapotranspiration water loss caused by temperature raise. Sediment yield (S) shows an inverted parabolic relationship with precipitation and at the same time positive correlation with glacier area ratio (Ag). The variation in sediment yield with precipitation can be explained by the operation of two factors, i.e., rainfall erosive action that increases continuously with increase in precipitation, and vegetation protective action that is unity for zero precipitation and decreases with increases in precipitation. 

How to cite: Zhang, F., Zeng, C., Wang, G., Wang, L., and Shi, X.: Spatial variation of runoff depth and sediment yield in relation to dominant Factors on the Tibetan Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1135, https://doi.org/10.5194/egusphere-egu22-1135, 2022.

In this paper, three parameterization schemes, one considering gravel influence (test1), one considering organic carbon influence (test2) and one comprehensively considering gravel and organic carbon influence (test3), were set up to modify different typical underlying surfaces of the Tibetan Plateau (TP). In addition, their soil thermal properties and hydraulic property variations were discussed. Additionally, discussing the key thermal and hydraulic parameters affected the performance of different schemes from the perspective of observation data in the TP to improve the simulation ability of soil temperature and soil moisture in the plateau areas. Compared the original Community Land Model (CLM) scheme, test1 resulted in higher soil temperature and lower soil moisture, while test2 had lower soil temperature and higher soil moisture. The key thermal and hydraulic parameters are the changes in the saturated thermal conductivity and the thermal conductivity of dry soil and the variations of the porosity and exponent B, respectively. The test3 scheme was the same as test2 for the modified changes of thermal properties, except that the proportion of change was slightly different. In terms of soil thermal properties, test2 and test3 were better at 0-20 cm depth, while test1 and test3 were better for the deeper (40 cm) simulation. Regarding hydraulic properties, the test1 and test3 schemes performed better on the Gobi and alpine meadows at 20-40 cm depth, while the original CLM scheme and test2 performed better on the underlying grassland surface. Test3 was better at balancing the relationship between the thermal and hydraulic parameters and could be used for the further research on the entire plateau area.

How to cite: Yuan, Y.: Modification and comparison of thermal and hydrological parameterization schemes for different underlying surfaces on the Tibetan Plateau in the warm season, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1291, https://doi.org/10.5194/egusphere-egu22-1291, 2022.

^{By using sounding data from Mount. Everest, Nyingchi, Nam Co, Nagqu and Shiquan River sites and ERA5 reanalysis data in 2104 and 2019. The characteristics of the temporal and spatial changes of the atmospheric boundary layer structure and its relationship with sensible heat, latent heat flux, and vertical velocity field, in order to deeply understand the different characteristics of the plateau atmospheric boundary layer structure under the coordinated action of westerly and monsoon and its change mechanism. The main findings of this study are as follows:}

^{(1)     The height of the convective boundary layer at each station under the westerly south branch wind field is higher than that under the summer monsoon wind field. The hight of convective boundary layers of Mount Everest, Nyingchi, Nam Co, Nagqu and Shiquan River under the westerly south branch wind field are 4500m, 3000m, 2400m, 2760m and 3500m. In the plateau monsoon field, the hight convective boundary layers are 3000 m, 2100 m, 2200 m, 1650 m and 2000 m.}

^{(2)     The specific humidity of the lower atmospheric boundary layer at each station under the westerly south branch wind field is smaller than that of the lower atmospheric boundary layer under the plateau monsoon wind field. The specific humidity of the near-surface layer in Linzhi area is obviously larger than that of the other four areas, and its maximum specific humidity is 12.88 g.kg-1. The lower layers of Mount Everest are often affected by the northerly valley wind at 14 o'clock and the glacier wind with southerly wind at 20 o'clock.}

^{(3)     The boundary layer has strong atmospheric turbulence and strong convection, which makes the boundary layer high. However, the latent heat flux at each station under the plateau summer monsoon wind field is large, and the moisture content in the air is large, which inhibits the development of the boundary layer.}

^{(4)     Convection in the boundary layer at each site is active during the day, with ascending and sinking movements alternately occurring. There was a strong sinking motion at Nyingchi Station at 14:00 on May 16th and October 25th, 2019, and at the same time, there was inverse humidity at the lower level. The vertical velocity in the atmospheric boundary layer of Nyingchi area is basically sinking. This may be one of the reasons that the height of the convective boundary layer in the Nyingchi area is lower than that of other stations, and it is also one of the reasons why inverse humidity often occurs in Nyingchi.}

^{Key words: the Tibetan plateau, South branch of westerly, Plateau monsoon, Atmospheric boundary layer}

How to cite: Li, M., Fu, W., Gong, M., Chang, N., Ma, Y., Hu, Z., Sun, F., and Yang, Y.: Study on the Land-Atmosphere Interaction in the Coordination Effect of Westerly Wind and Monsoon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1028, https://doi.org/10.5194/egusphere-egu22-1028, 2022.

Using data from cloud radar, ground observations and ERA5 reanalysis data, factors influencing nighttime precipitation during summer in the Yushu area of the Tibetan Plateau (TP) are investigated. The cloud top height (CTH), cloud base height (CBH) and liquid water content (LWC) are compared between the non-precipitating days and precipitating days. The results show that the average CTH during precipitating days over Yushu is below 10 km above ground level (hereafter AGL) in the daytime, while it is more than 10 km AGL at night with the maximum at 23 Beijing Standard Time (BST, = Coordinated Universal Time + 8 hour). The CBH is in phase with the dew-point spread. The precipitation intensity and CTH is in phase with the LWC. The hourly averaged precipitation intensity and convective available potential energy (CAPE) in ERA5 reach the maximum at 21 BST, which is 3 hours ahead of the observations. There is downward motion flow at noon during non-precipitating days, while there is upward motion flow at night during the precipitating days. In addition, the horizontal wind direction in the lower level (below 5000 m) shows clockwise rotation from morning to night. Wind shear occurs in the middle level of the atmosphere, is accompanied by subtropical westerly jet in the upper level. The difference of horizontal wind speed between the level of 200 hPa and 500 hPa is positively related to the LWC, making contribution to the formation of upper-level clouds

How to cite: Cao, B.: Factors Influencing Diurnal Variation Of Cloud And Precipitation In the Yushu Area, Tibetan Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1272, https://doi.org/10.5194/egusphere-egu22-1272, 2022.

Precipitation studies suggest an accelerated water cycle over the Tibetan Plateau (TP) in recent decades. However, the exact changes to evapotranspiration (ET_a) over this period remain largely unknown. Multiple ET_a products for the TP region report that ET_a experienced a significant increasing trend of around 8.4 ± 2.2 mm/10 a during 1982–2018. Here, we quantified and explained the ET_a trend using a comprehensive process-based ET_a model refined on ground-based observations over the TP. Attribution analysis revealed that a large part of the increasing ET_a trend was caused by higher temperature (53.8%) and more soil moisture (23.1%) caused by the melting cryosphere and increased precipitation. The increasing rate of ET_a on the TP was approximately twice that of the global ET_a, providing strong and independent evidence for an accelerated hydrological cycle. The dominant role of increased temperature in ET_a implies a continued acceleration of the water cycle in the future.

How to cite: Yuan, L., Chen, X., Ma, Y., Chen, D., Su, Z., Cao, D., Wang, B., Han, C., Ma, W., and Menenti, M.: Significantly increased evapotranspiration reveals accelerated water cycle on the Tibetan Plateau during 1982–2018, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1421, https://doi.org/10.5194/egusphere-egu22-1421, 2022.

By integrating data from 25 flux observation sites in the alpine grasslands of the Tibetan Plateau with corresponding remote sensing and reanalysis data, a data-driven Extremely Randomized Trees regression (ETR) was used to estimate the NEE of alpine grasslands on the Tibetan Plateau from 1982-2018. The spatial and temporal variation patterns of the NEE were also analyzed. The results show that the annual mean NEE of alpine meadows on the Tibetan Plateau from 1982 to 2018 was -35.59 g C m^-2 yr^-1, and showed a significant decreasing trend at -0.78 g C m^-2 yr^-1; on the spatial scale, the alpine meadows in the relatively wet eastern and northeastern parts of the Tibetan Plateau were strong carbon sinks with the intensity around -150 ~ -100 g C m^-2 yr^-1. From the alpine meadows in the east to the semi-arid or arid alpine grasslands in the west and north, the carbon sink intensity gradually decreased along the longitudinal gradient and becomes a weak carbon sink or a weak carbon source (0 ~ ± 20 g C m^-2 yr^-1). The sensitivity analysis showed that precipitation and mean temperature contributed significantly to the interannual trend variation of NEE in grasslands on the Tibetan Plateau during the 1982-2018. The contribution of precipitation was large in the alpine steppe region in the western and northwestern part of the plateau, while the contribution of mean temperature was highest in the alpine meadow region in the east and south, where precipitation dominated 84% of the interannual NEE variation of the entire alpine steppe region, while mean temperature accounts for 55% of that of the alpine meadow region. In general, the interannual variability of NEE in the alpine steppe region tended to be dominated by precipitation, while the alpine meadow region tended to be regulated by temperature. In addition, the NEE of alpine meadow region showed a significant decreasing trend with -0.91 and -0.67 g C m^-2 yr^-1 during 1982-1999 and 2000-2018, respectively, while the alpine steppe region showed a non-significant decreasing trend change with -0.37 and -0.19 g C m^-2 yr^-1, respectively. The different changes of NEE in different vegetation type regions at different time periods were mainly caused by the changes of temperature and precipitation.

How to cite: Wang, Y. and Ma, Y.: Spatio-temporal patterns of NEE based on upscaling eddy covariance measurements in the alpine grassland of the Tibetan Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1440, https://doi.org/10.5194/egusphere-egu22-1440, 2022.

Tibetan Plateau Observation Platform (TORP), Third Pole Environment (TPE) observation and research Platform (TPEORP) and new stations were set up in recently years.
Firstly, based on the difference of model and in-situ observations, a serious of sensitive experiments were done by using numerical model, Such as Noah-MP and WRF. Better schemes in ground temperature and soil water content at shallow layer simulation were selected by comparing with Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature and Soil Moisture Active Passive (SMAP) soil moisture data. In order to use remote sensing products, a land-atmosphere model was initialized by ingesting land surface parameters, such as AMSR-E RS products, and the results were compared with the default model configuration and with in-situ long-term CAMP/Tibet observations. 
Secondly, we analyzed the spatiotemporal variation characteristics of the heating field in the Tibetan Plateau through the observation data and reanalysis data and then revealed the influencing factors and potential effects of the changes of atmospheric heat sources on the Tibetan Plateau in summer and winter. Finally, the relationship between the change of spring AHS in the Tibetan Plateau and the change of summer precipitation in Northeast China was also analyzed from the level of mathematical statistics.
Thirdly, based on historical observations daily data for 1981-2016 from 130 meteorological stations over and around the Tibetan Plateau , the trends of sensible heat flux (SH) and their elevation-dependence were investigated. Results indicate that the SH over and around the Tibetan Plateau experienced apparent trends’ shift in approximate 2000, demonstrating noticeable reductions during 1981-2000 and pronounced recovery during 2001-2016 for the four seasons.
All of the different methods will clarify the water and energy parameters in complex plateau, it also can affect atmospheric cycle over the Tibetan Plateau even all of the global atmospheric cycle pattern.

How to cite: Ma, W., Ma, Y., Han, Y., Hu, W., Zhong, L., Xie, Z., Hu, Z., Su, R., He, J., Ma, W., Bai, L., and Sun, F.: In-situ observation, modeling and analysis for water and energy parameters over the Tibetan Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1471, https://doi.org/10.5194/egusphere-egu22-1471, 2022.

Actual evapotranspiration (ETa) is a key variable in the energy and water cycle of the earth climate system. Evapotranspiration product with high temporal resolution and accuracy is of great significance to the effective use of water resources and regulation of local climate. Here, one–year hourly ETa over the entire Tibetan Plateau (TP) was estimated by a combination use of satellite data from Fengyun-4A and Random Forest (RF) model. The validation against in situ measurements from six stations equipped with eddy-covariance instruments shows a root mean square error (RMSE) of 32.24 mm month^-1 and a correlation coefficient of 0.85. Compared with results from surface energy balance system (SEBS) with a RMSE value of 59.13 mm month^-1, Maximum Entropy Production (MEP) with a RMSE value of 62.28 mm month^-1 and the European Centre for Medium-Range Weather Forecasts Reanalysis-5 (ERA5) with a RMSE value of 53.64 mm month^-1, the ETa results from RF model have the highest accuracy. The annual spatial average RF ETa over the whole TP was about 387.34 mm. Thus, the total ETa of the TP was about 1039.85 km³ yr⁻¹. The annual average ETa in the eastern (long. > 95°E), central (95°E ≥ long. > 85°E) and western (long. ≤ 85°E) parts of the TP are 478.63 mm, 356.94 mm and 279.67 mm, respectively. In addition, diurnal averaged and monthly averaged ETa over different land cover types and different climate zones over the TP were also clearly identified. The ETa over cropland and the humid area is the highest with the largest variation range.

How to cite: Wang, X., Zhong, L., Ma, Y., Ma, W., and Han, C.: Estimation of hourly actual evapotranspiration over the Tibetan Plateau by random forest model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1605, https://doi.org/10.5194/egusphere-egu22-1605, 2022.

The Yarlung Zangbo Grand Canyon (YGC) is an important pathway for water vapor transport from south Asia to the Tibetan Plateau (TP). This area exhibits one of the highest frequencies of convective activity in China, and precipitation often brings natural disasters to local communities that can dramatically affect their livelihoods. In addition, the produced precipitation has produced vast glaciers and large rivers around the YGC. In 2018, the Second Tibetan Plateau Scientific Expedition and Research Programme tasked a research team to conduct an "Investigation of the water vapor channel of the Yarlung Zangbo Grand Canyon" in the southeastern Tibetan Plateau. This team subsequently established a three-dimensional comprehensive observation system of land-air interaction, water vapor transport, cloud cover, and rainfall activity in the YGC. This paper introduces the developed observation system and summarizes preliminary results obtained during the first two years of the project. Using this observation network, we focus herein on the development of heavy rainfall events in southeast Tibet that are associated with water vapor transported from the south. This project also helps to monitor geohazards in the key area of the Sichuan-Tibet railway that traverses the northern YGC.

How to cite: Chen, X., Xu, X., Wang, G., Chen, D., Ma, Y., Liu, L., Hu, X., Liu, Y., Li, L., Li, M., Ming, G., Luo, S., and Wang, X.: INVC-Investigation of the water vapor channel within the Yarlung Zangbo Grand Canyon, China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2088, https://doi.org/10.5194/egusphere-egu22-2088, 2022.

Land-atmosphere interactions are an essential component of the climate system. However, no detailed description of the underlying effects of the surface forcing of the atmosphere has been established. In this study, GLEAM, MODIS, and ERA5 were the input set of multiple analysis algorithms, "segmentation" was the core idea of the analysis method. The study area is segmented into six surface response functional groups, and the multidimensional evaporation regime function was segmented into piecewise functions controlled by segment authoritative variables. Inspired by the surface heat balance equation and moisture-limited, energy-limited evaporation regimes, we chose soil moisture content and the net radiation flux to represent the moisture and energy status, respectively, and chose the leaf area index (LAI) to characterize the vegetation cover to investigate the primary effects of surface parameters on the energy partitioning of the land surface and evaporative regime. The results show that though a coupling strength 1.8 times greater was obtained when the LAI was used as the explanatory variable instead of soil moisture, soil moisture was still the highest explanatory variable in the regression tree analysis. This is consistent with the essence of the evaporative fraction and indicates that water should be the most fundamental explanatory variable. The evaporative regime was subdivided from two phases into five phases according to the effects such as water extraction by vegetation, photosynthesis, soil shading, and roughness changes, each with an authoritative explanatory variable.

How to cite: Yang, C.: Terrestrial and Atmospheric Controls on Surface Energy Partitioning and Evaporative Fraction Regimes Over the Tibetan Plateau in the Growing Season, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2633, https://doi.org/10.5194/egusphere-egu22-2633, 2022.

After the considerable lake level decrease in 2015 in response to the super 2015/2016 El Niño and lake level recovery in 2016, an extreme lake expansion occurred on the central and northern TP in the following two years (2017 and 2018), in contrast with the slight lake level changes on the southern TP. In-situ observations at Zhari Namco near Cuoqing County show that lake level increased abruptly by 1.4 m and 1.7 m in summer 2017 and 2018, respectively, which was even close to the accumulated lake level increase between 2000 and 2015. At Dazeg Co near Nima Country, lake level increased by 0.9 m and 1.4 m in summer 2017 and 2018, respectively, which is about 3 times as large as the increasing rate between 2000 and 2015. At Eya Co and Cedo Caka near Shuanghu County, lake level accumulatively increased by 1.5 m and 2.0 m, respectively, in the two years. The extreme lake expansion had significant impact on geomorphology and even posed great threat on the infrastructures such as road and bridges around the lakes. Causes of the extreme lake expansion are investigated by examining precipitation data and changes in large scale circulations. 

How to cite: Lei, Y., Yao, T., Sheng, Y., Yang, K., and Zhou, J.: Extreme lake expansion on the Tibetan Plateau: Observations and consequences, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6770, https://doi.org/10.5194/egusphere-egu22-6770, 2022.

Meteorological variables (e.g. air temperature (T2), radiation flux and precipitation) determine the evolution of glacier mass and characteristics. Observations of these variables are not available at adequate spatial coverage and temporal / spatial resolution over the Tibetan Plateau. This study focuses on evaluating the performance of albedo parameterization scheme in WRF coupled with Noah-MP in terms of glacio-meteorological variables, by conducting sensitivity experiments on Parlung No. 4 Glacier in ablation season in 2016. The control experiment (CTL) uses the model’s default albedo scheme and unrealistic surface type, while sensitivity experiments apply the default albedo scheme (Sens1) and the modified scheme (Sens2) in ice surface. The key results are as follows. First, all experiments yield similar T2 diurnal patterns to the observations and realistic land-use type considerably reduces model warm bias on the glacier. The RMSE of T2 decreases by 1 °C with an improvement of 37 % by sensitivity experiment estimates. Second, Sens1 keeps rather high albedo value of 0.68 causing net shortwave radiation and net radiation apparent underestimation, while Sens2 holds mean albedo value of 0.35 close to observations contributing to relieve net shortwave radiation and net radiation underestimation. Thirdly, compared with Sens1 estimates, more energy from Sens2 is used to heat ice surface resulting in high ground heat flux (182 W m^-2), ice melt and liquid water content increase more quickly and preferentially. Our study confirms the ability of WRF model in reproducing glacio-meteorological variables as long as a reasonable albedo parameterization scheme is applied, and provides a theoretical reference for researchers committed to further improving the surface albedo scheme.

How to cite: Liu, L. and Ma, Y.: Evaluation of albedo schemes in WRF coupled with Noah-MP on the Parlung No. 4 Glacier against in-situ observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8345, https://doi.org/10.5194/egusphere-egu22-8345, 2022.

Blowing snow processes are crucial in shaping the strongly heterogeneous spatiotemporal distribution of snow and in regulating subsequent snowpack evolution in mountainous terrain. Although empirical formulae and constant threshold wind speeds have been widely used to estimate the occurrence of blowing snow in regions with sparse observations, these methods struggle to accurately capture the high local variability of blowing snow. This study investigated the potential capability of the decision tree model to detect blowing snow occurrence based on routine meteorological observations (mean wind speed, maximum wind speed, air temperature and relative humidity) and snow measurements. Results show that the maximum wind speed contributes the most to the classification accuracy, and the inclusion of more predictor variables improves the overall accuracy. Besides, the overall accuracy of blowing snow occurrence detected by the decision tree model is comparable or even better than traditional methods, indicating it is a promising approach requiring limited meteorological variables and having the potential to scale to multiple stations across different regions, such as the Tibetan Plateau.

How to cite: Xie, Z., Ma, Y., Ma, W., and Hu, Z.: Detecting occurrence of blowing snow events with decision tree model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9708, https://doi.org/10.5194/egusphere-egu22-9708, 2022.