HS6.10

The High Mountains of Asia (HMA) region and the Tibetan Plateau (TP), with an average altitude of 4000 m, are hosting the third largest reservoir of glaciers and snow after the two polar ice caps, and are at the origin of strong orographic precipitation. Climate studies over HMA are related to serious challenges concerning the exposure of human infrastructures to natural hazards and the water resources for agriculture, drinking water, and hydroelectricity to whom several hundred million inhabitants of the Indian subcontinent are depending. However, climate variables such as temperature, precipitation, and snow cover are poorly described by global climate models because their coarse resolution is not adapted to the rugged topography of this region. Since the first CMIP exercises, a cold model bias has been identified in this region, however, its attribution is not obvious and may be different from one model to another. Our study focuses on a multi-model comparison of the CMIP6 simulations used to investigate the climate variability in this area to answer the next questions: (1) are the biases in HMA reduced in the new generation of climate models? (2) Do the model biases impact the simulated climate trends? (3) What are the links between the model biases in temperature, precipitation, and snow cover extent? (4) Which climate trajectories can be projected in this area until 2100? An analysis of 27 models over 1979-2014 still show a cold bias in near-surface air temperature over the HMA and TP reaching an annual value of -2.0 °C (± 3.2 °C), associated with an over-extended relative snow cover extent of 53 % (± 62 %), and a relative excess of precipitation of 139 % (± 38 %), knowing that the precipitation biases are uncertain because of the undercatch of solid precipitation in observations. Model biases and trends do not show any clear links, suggesting that biased models should not be excluded in trend and projections analysis, although non-linear effects related to lagged snow cover feedbacks could be expected. On average over 2081-2100 with respect to 1995-2014, for the scenarios SSP126, SSP245, SSP370, and SSP585, the 9 available models shows respectively an increase in annual temperature of 1.9 °C (± 0.5 °C), 3.4 °C (± 0.7 °C), 5.2 °C (± 1.2 °C), and 6.6 °C (± 1.5 °C); a relative decrease in the snow cover extent of 10 % (± 4.1 %), 19 % (± 5 %), 29 % (± 8 %), and 35 % (± 9 %); and an increase in total precipitation of 9 % (± 5 %), 13 % (± 7 %), 19 % (± 11 %), and 27 % (± 13 %). Further analyses will be considered to investigate potential links between the biases at the surface and those at higher tropospheric levels as well as with the topography. The models based on high resolution do not perform better than the coarse-gridded ones, suggesting that the race to high resolution should be considered as a second priority after the developments of more realistic physical parameterizations.

How to cite: Lalande, M., Ménégoz, M., and Krinner, G.: Climate change in the High Mountain Asia simulated with CMIP6 models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8365, https://doi.org/10.5194/egusphere-egu21-8365, 2021.

This study investigates the controlling factors of the interannual variability of Tibetan Plateau snow cover (TPSC) in winter. Since snow observation in Tibetan Plateau is limited in space and time, high-resolution multi-satellite data for TPSC were analyzed during 1982-2016. In addition, a large ensemble AGCM experiment from d4PDF (hereafter, HIST), driven by observed SST and anthropogenic forcings were analyzed during 1951-2010 to compare the contributions arising from internal variability and external forcings including the change in greenhouse gases (GHGs) concentration on TPSC variation. In this study TPSC fraction (hereafter, TPSCF) is defined as the percentage of the snow-covered area over the Tibetan Plateau. For both observation and HIST, high and low TPSCF years determined by the standardized January-March TPSCF were analyzed. The range of interannual TPSCF variation (i.e., TPSCF difference between high and low TPSCF years) is about 11% in both observation and the model, suggesting the AGCM well reproduced the TPSCF variability in the interannual timescale. 

We found that high TPSCF is linked to a positive-AO-like pattern. The interannual variation of the observed AO index and TPSCF are significantly correlated. In d4PDF high TPSCF more likely appears with a higher (positive) AO index and vice versa. In high TPSCF years, the subtropical jet is strengthened, which significantly enhances zonal water vapor flux reaching the plateau supporting more precipitation. Another interesting result is a disagreement for ENSO’s contribution to TPSC appears between observation and HIST. However, several members in HIST show a feature close to the observation, in which TPSCF anomalies are not sensitive to the El Niño/La Niña events. Thus, this weak linkage between ENSO and TPSCF is more likely due to the limited cases of observations rather than the model bias. Finally, by comparing HIST and non-warming experiments (NAT), we found historical global warming has decreased the snow-to-rain ratio over TP. Nonetheless, increased precipitation compensates for it. As a result, the impact of historical global warming on TPSCF could be considered negligibly weak.

How to cite: Li, S., Sato, T., and Nakamura, T.: Historical change of winter Tibetan Plateau snow cover and its controlling factors, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6877, https://doi.org/10.5194/egusphere-egu21-6877, 2021.

 ^{Different underlying surfaces have differing diversities, complex compositions and uneven distributions and contribute to diverse and complex land surfaces. As the main input factor for atmospheric energy, the surface greatly affects the various interactions between the ground and the atmosphere and even plays a key role in local areas on the Tibetan Plateau. The characteristics of the atmospheric boundary layer structure of the plateau and the land-atmosphere interaction under the control of different wind fields in the south branch of the westerly wind and the plateau monsoon are discussed. Results show that the height of the atmospheric boundary layer at each station under the westerly south branch wind field is higher than that under the summer monsoon wind field. The height of the convective boundary layers of Mount Everest, Nyingchi, Nagqu and Shiquan River in the southwest wind field are 3250 m, 2250 m, 2760 m and 3500 m. while the height of the convective boundary layers of Mount Everest, Nyingchi, Nagqu and Shiquan River under the plateau monsoon field are 2000 m, 2100 m, 1650 m and 2000 m. The specific humidity of the surface layer at all site is larger on July than it on other months. The specific humidity of the surface layer in Linzhi area is larger than that of the other three regions, and it reaches 12.88 g·kg-1 at the maximum. The wind direction on Mount Everest over 1200 m is dominated by westerly winds in May and October. The wind direction on Nyingchi above 1500 m is dominated by westerly winds in May and October, and in July, winds above 1200 m is dominated by southerly winds. The wind direction of Shiquan River in May and October is dominated by west-southwest wind, and the wind direction of Shiquan River in July is dominated by west-northwest wind. Secondly, variation characteristics of surface fluxes were analyzed by using the eddy covariance observations from four stations of Pailong(entrance of Canyon), Danka (middle of Canyon), Kabu (end of Canyon) , and Motuo (end of Canyon) in the southeastern gorge area of Tibet. The changing trend of monthly averaged daily sensible heat flux at Kabu station is fluctuating. Sensible heat flux and latent heat flux at Motuo station have the same variation characteristics. Latent heat fluxes increase first and then decrease at all four stations. Seasonal variations of soil heat flux are obvious, characterizing positive values in spring and summer and negative values in autumn and winter. The diurnal variation intensity of net radiation flux is summer>spring>autumn>winter.   Energy closure rates of Danka, Pailong, Motuo, and Kabu stations are 70.86%, 68.91%, 69.29%, and 67.23%, respectively. Latent heat fluxes and soil heat fluxes increase, and sensible heat fluxes decrease as increasing precipitation at the four stations. The sensible heat flux and soil heat flux respond synchronously to precipitation changes, and the changes in latent heat have a significant lag in response to precipitation changes.}

How to cite: Li, M., Wang, L., Fu, W., Gong, M., and Chang, N.: Study on the Land-Atmosphere Interaction in the Coordination Effect of Westerly Wind and Monsoon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2318, https://doi.org/10.5194/egusphere-egu21-2318, 2021.

In this paper, the impact of gravel is taken into account in regional simulations on the Tibetan Plateau (TP). The differences of ground surface and soil hydrological processes in the TP are compared when the gravel parameterization schemes and the original soil hydrothermal parameterization schemes are respectively adopted in the regional climate model version 4.7 (RegCM4.7), which is driven by the EIN15. Moreover, the performances in simulating the liquid soil moisture (LSM) by using the two schemes are also assessed. When the impact of gravel is considered, the changes of ground hydrological processes are consistent with those of liquid precipitation and snow meltwater except the infiltration, indicating the dominance of liquid precipitation and snow meltwater in ground hydrological processes. The lower gravel content will facilitate the downward transportation of LSM. However, in the case of high gravel content, the roles of gravel content are completely opposite in the western and central TP. The most obvious change is that the simulated LSM by the gravel schemes is lower at most soil depths compared with that by the original schemes, which is beneficial in most cases. For instance, the mean absolute errors of the reference data with the simulations by the gravel schemes and original schemes at the soil depth of 0.1 m in the southeastern TP are 0.026 and 0.101, respectively. Besides the southeastern TP, the performance in simulating the temporal variation of the LSM below the middle soil layers still needs to be improved.

How to cite: Liu, Y., Lyu, S., Ma, C., Xu, Y., and Luo, J.: The Gravel Parameterization Schemes on Tibetan Plateau and Its Assessment Using RegCM4, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5201, https://doi.org/10.5194/egusphere-egu21-5201, 2021.

As the highest plateau in the world, the Tibetan Plateau (TP) exerts great impacts on regional and global climate and water cycle through interactions between land and free atmosphere. Terrestrial evapotranspiration is a critical component of the Earth's water cycle. To better understand the heterogeneity of the evapotranspiration over the Tibetan Plateau and its influences, we conducted a whole year dynamical downscale modelling (DDM) with the horizontal resolution at 28km and a convection permitting modelling (CPM) at 4km for 2014. DDM and CPM simulation results are compared with an satellite retrieving dataset, which is referred as OBS in the following, the global land surface data assimilation system (GLDAS) and two commonly used reanalyses ERA-Interim and ERA5, as well. The annual and seasonal means and seasonal variabilities are inter-compared. The evapotranspiration over ten dominant land use types are investigated based on six datasets. Differences with the satellite dataset are illustrated and relationships with soil moisture and temperature, precipitation and radiation are explored. The followings are obtained. GLDAS generally reproduces magnitude and pattern of the OBS; reanalyses overestimate, DDM and CPM underestimate compared to the OBS and GLDAS.

The overestimations in reanalyses occur in the monsoon season and the underestimations in DDM and CPM occur in the non-monsoon season. Large evapotranspiration biases exist over the vegetated ground which exert large impacts on the TP-average biases for growing season.

How to cite: Dan, J. and Gao, Y.: Detecting evapotranspiration biases in reanalyses and regional climate modeling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7076, https://doi.org/10.5194/egusphere-egu21-7076, 2021.

This study analyses the diurnal seasonal mean and the seasonal and annual variation in the radiation budget at the Ali Meteorological Bureau observation station in the northern Tibetan Plateau for 2019. The results indicate that the daily average variation in incidental shortwave and reflected radiation across all seasons in the Ali area had typical unimodal symmetry. The average daily variation in incidental shortwave radiation was in phase with reflected radiation, but the amplitude of the incidental shortwave radiation was greater than that of reflected radiation. The daily amplitude, daily average, and monthly average upwelling longwave radiation were greater than those for downwelling radiation, and the diurnal cycle of downwelling atmospheric radiation lagged behind that of upwelling longwave radiation. The daily amplitude of surface net radiation in winter in the Ali area was less than in other seasons, as expected, and the seasonal transformation had a great impact on the net radiation for this region. The net radiative energy at the surface was highest in late spring and early summer, which played a decisive role in the formation of terrestrial and atmospheric heating.

How to cite: Wang, G. and Han, L.: Surface Radiation Characteristics of the Ali Area, Northern Tibetan Plateau, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7059, https://doi.org/10.5194/egusphere-egu21-7059, 2021.

Snowfall is a key component of the hydrological system of the Tibetan Plateau (TP), and it is also a very sensitive factor to climate change. To understand the mechanism of extreme snowfall in different regions of the TP, we used the 50-year snow depth data from the China Meteorological Administration (CMA) ground observations and the ERA5 reanalysis datasets of European Centre for Medium-Range Weather Forecasts (ECMWF). Results show the threshold of extreme snow in the southern TP is four times greater than that in the eastern region. Sixteen numerical experiments using the weather research and forecasting (WRF) model were conducted to quantify the contribution of water vapor and dynamic conditions to snowfall events. Here are the preliminary results: (1) For the snowfall event caused by local circulation in the eastern TP, the contribution of dynamic conditions is greater than that of moisture conditions. An increase of 10% in the wind field (water vapor) will enhance the snow water equivalent (SWE) by more than 25% (10%). (2) For large-scale circulation, q has a greater effect. But the overall increase in snowfall is smaller than the local circulation. (3) The severe snowfall frequently takes place in the southern TP, where water vapor channel and topographic uplift are significant factors to snowfall. we think the southern simulation will produce interesting results. Our results will provide scientific reference in improving the snowstorm forecasting and disaster prevention and mitigation.

How to cite: Yao, N., Liu, L., and Ma, Y.: The different mechanisms of extreme snowfall in the eastern and southern Tibetan Plateau., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14593, https://doi.org/10.5194/egusphere-egu21-14593, 2021.

Permafrost degradation under global warming may change the hydrological regime of the headwater catchments in alpine area such as the Tibetan Plateau (TP). In this study, he runoff generation processes in permafrost-influenced area of the Heihe River Headwater were investigated with the following results: 1) The observed stable isotope values of various water types on average was roughly in the order of snowfall and snowmelt < bulk soil water (BSW) < rainfall , stream water, mobile soil water (MSW) , and lateral subsurface flow. The depleted spring snowmelt and enriched summer rainfall formed tightly bound soil water and MSW, respectively. The dynamic mixing between tightly bound soil water and MSW resuted in BSW with more depleted and variable stable isotopic feature than MSW. 2) Along with the thawing of the frozen soil, surface runoff and shallowsubsurface flow (SSF) at 30−60 cm was the major flow pathway in the permafrost influenced alpine meadow hillslope during spring snowmelt and summer rainfall period, reapectively, with the frozen soil maintaining supra-permafrost water level. 3) Comparison between two neighouring catchments under similar precipitation conditions indicated that streamflow of the lower catchment with less permafrost proportion and earlier thawing time has larger SSF and higher based flow component, indicating the potential changes of hydrological regims subject to future warming.

How to cite: Zhang, F., Xiao, X., and Wang, G.: Runoff generation processes in permafrost-influenced area of the Heihe River Headwater, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1660, https://doi.org/10.5194/egusphere-egu21-1660, 2021.

Serious soil erosion is observed during the spring because soil thawing coincides with the period of snowmelt and low meadow coverage at this time. Studies relating to soil erosion caused by spring meltwater are limited and controversial. In this study, a field experimental study was conducted in an alpine meadow slope in the Binggou watershed on the northern edge of the Tibetan Plateau to assess the impact of multiple factors on spring meltwater erosion. The multiple factors included three flow rates, four slope gradients, and three underlying surface conditions (meadow, disturbed meadow, and alluvial soil). An equal volume of concentrated meltwater flow was used in all experiments. The results showed that rapid melting at a high flow rate could accelerate soil erosion. The influence of the slope gradient on the amount of runoff was positively linear and the influence was relatively low. However, the slope gradient had a strong impact on soil erosion. The meadow could effectively reduce soil erosion, although when the meadow was disturbed, the total runoff increased by 60% and the sediment yield by a factor of 1.5. The total runoff from the alluvial soil doubled in comparison to the meadow, while the sediment yield increased nearly 7-fold. The findings of this study could be helpful to understand the characteristics and impact of multiple controlling factors of spring meltwater erosion. It also aims to provide a scientific basis for an improved management of alpine meadows as well as water and soil conservation activities in high-altitude cold regions.

How to cite: Shi, X., Zhang, F., and Wang, L.: The effects of multiple factors on spring meltwater erosion on an alpine meadow slope, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16555, https://doi.org/10.5194/egusphere-egu21-16555, 2021.

The South Asian summer monsoon (SASM) system is one of the most energetic regional monsoon systems. Its onset and demise timings determine the propagation, duration, and magnitude of precipitation through thermodynamic and dynamic processes in the SASM-prevailing areas. Particularly, anomalous onsets and demises of the SASM could generate a large anomaly in precipitation and serious water-related disasters over the SASM-prevailing areas.

The South-Central Tibetan Plateau (SCTP), known as the “Asian water tower”, is the origin of several major Asian rivers, including the Yellow River, Yangtze River, Brahmaputra River, Mekong River, and the Indus River, providing a huge amount of freshwater for ecosystems and billions of people in Asia. It is widely known that the SCTP is controlled by the SASM system in summer, accounting for approximately 60% of annual precipitation, but with significant spatiotemporal heterogeneity due to the complex topographic and geographic conditions. Presently, most studies have focused on the effects and physical causes of the linear trend of SASM onset over the SCTP. However, little attention has been paid to the question as to how both anomalous onset and anomalous demise of the SASM influence the interannual precipitation variation in this region. In particular, the spatial manifestation of thermodynamic and dynamic mechanisms for the interannual precipitation variation is largely unknown. Adequate knowledge about these mechanisms is critical for sustainable freshwater management and water disasters control in this region and surrounding areas.

These call a detailed study to investigate the influences of the early and late onset (demise) of the SASM system on the interannual variations in precipitation and their underlying mechanisms over the SCTP. In this study, we mainly clarify the following key questions: (1) How do the onset and demise of the SASM control the interannual variations in precipitation over the SCTP? (2) Is there an asymmetric effect of the SASM on SCTP precipitation between its onset and demise, and between its early and late onset (demise)? and (3) What are the underlying mechanisms that are responsible for the variations in interannual precipitation? The results would help improve our understanding of the SASM-precipitation relationship over the SCTP and alleviation of water-related disasters in the region.

How to cite: Zhu, Y., Sang, Y.-F., Chen, D., Sivakumar, B., and Li, D.: How does the South Asian summer monsoon anomaly influence the interannual variations in precipitation over the South-Central Tibetan Plateau, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3669, https://doi.org/10.5194/egusphere-egu21-3669, 2021.

Carbonaceous particles play an important role in climate change, and the increase in their emission and deposition causes glacier melting in the Himalayas and the Tibetan Plateau (HTP). This implies that studying their basic characteristics is crucial for a better understanding of the climate forcing observed in this area. Thus, we investigated characteristics of carbonaceous particles at Yaze village, a typical remote site of southeastern HTP.  The results showed that the organic carbon and elemental carbon concentrations at this study site were 1.86 ± 0.84 and 0.18 ± 0.09 μg m^-3, respectively, which were much lower than those reported for other frequently monitored stations in the same region. Thus, these values reflect the background characteristics of the study site. Additionally, the absorption coefficient per mass (α/ρ) of water-soluble organic carbon (WSOC) at 365 nm was 0.60 ± 0.19 m² g^-1, which was lower than those reported for other remote stations in the HTP. This value could be attributed to a lower and higher contribution of mineral dust and secondary organic carbon, respectively. Multi-dimensional fluorescence analysis showed that the WSOC consisted of approximately 37% and 63% protein and humic-like components, respectively, and the latter was identified as the determining component of light absorption ability of the WSOC. Combined the significant relationships between WSOC and sulfate ion, potassium ion, and nitrate ion with the air masses at the study site originated primarily from South Asia, it is suggested that the levels of carbonaceous particles in Yaze village were predominantly influenced by emissions from South Asia.

How to cite: Zhang, C., Chen, M., Kang, S., Yan, F., and Li, C.: Light absorption and fluorescence characteristics of water-soluble organic compounds in carbonaceous particles at a typical remote site in the southeastern Himalayas and Tibetan Plateau, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3653, https://doi.org/10.5194/egusphere-egu21-3653, 2021.

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) observation and research Platform (TPEORP) is now implementing over the Third Pole region. The background of the establishment of the TPEORP, 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 and latent heat flux (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 and latent heat flux 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. The sensible heat flux has increased slightly and the latent heat flux has decreased from 2001 to 2018 over the TP. 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., Hu, Z., Wang, B., Zhong, L., Ma, W., Han, C., Chen, X., Liu, L., Subba, S., Xie, Z., and Wang, Y.: The observation and modeling of air-land interaction over heterogeneous landscapes of the Third Pole, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1559, https://doi.org/10.5194/egusphere-egu21-1559, 2021.

As region that is highly sensitive to global climate change, the Tibetan Plateau (TP) experiences an intra-seasonal soil water deficient due to the reduced precipitation during the South Asia monsoon (SAM) break. Few studies have investigated the impact of the SAM break on TP ecological processes, although a number of studies have explored the effects of inter-annual and decadal climate variability. In this study, the response of vegetation activity to the SAM break was investigated. The data used are: (1) soil moisture from in situ, satellite remote sensing and data assimilation; and (2) the Normalized Difference Vegetation Index (NDVI) and Solar-Induced chlorophyll Fluorescence (SIF). We found that in the region impacted by SAM break, which is distributed in the central-eastern part of TP, photosynthesis become more active during the SAM break. And temporal variability in the photosynthesis of this region is controlled mainly by solar radiation variability and has little sensitivity to soil moisture. We adopted a diagnostic process-based modeling approach to examine the causes of enhanced plant activity during the SAM break on the central-eastern TP. Our analysis indicates that active photosynthetic behavior in the reduced precipitation is stimulated by increases in solar radiation absorbed and temperature. This study highlights the importance of sub-seasonal climate variability for characterizing the relationship between vegetation and climate.

How to cite: Ren, Y., Yang, K., and Wang, H.: The South Asia Monsoon Break Promotes Grass Growth on the Tibetan Plateau, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5776, https://doi.org/10.5194/egusphere-egu21-5776, 2021.

Precipitation usually is the main source of river discharge in the high mountain headwater areas and therefore as a key parameter in hydrological modelling. However, spatiotemporal distribution of precipitation in the remote high mountain headwater areas on the Tibetan Plateau (TP) has been poorly described due to the scarce meteorological stations located in high elevations. A series of rain gauges were set-up in three catchments of the southern TP to study their precipitation (liquid) gradient (PG) characteristics under different precipitation intensity grades (PIG) during the monsoon season (July to September) from 2013 to 2016. Results showed that the average PG varied during 0.71 to 0.82 mm·100 m^-1 in the three study catchments for the total (non-intensity-graded) precipitation during the monsoon, and varied up to 2.4 times under different PIGs. Besides, PGs were all strongly correlated to precipitation amounts in the three study catchments, these patterns were relatively persistent among different years but varied among different catchments. Generally, the correlations between PG and precipitation amount showed a steep positive slope under fine precipitation grade but became flat or even negative with stronger PIG. We concluded that the precipitation in southern Tibet was influenced more by valley-scale convection than by large-scale vapor circulation during the monsoon season.

How to cite: Zeng, C. and Zhang, F.: Study on the precipitation gradient characteristics in the high mountains of southern Tibet, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16557, https://doi.org/10.5194/egusphere-egu21-16557, 2021.

Being an important water resource of the local and downstream living hoods, precipitation amount is experiencing drastic changes in the Babao River basin in the northeast of the Tibetan Plateau. Precipitation types also have great impacts on the runoff. However, in usual cases, weather stations only record precipitation amount without discriminating its type. Here, we compared results from three methods at improving precipitation type (solid and liquid) estimation with discontinuous 24 years precipitation type records of the Qilian gauging station. The results (bias rank of the three methods is 2.5% < 17.3% < 20.1%) showed that the estimation of different thresholds for wet season (4 °C) and dry season (5.5 °C) is the closest to the actual records. Based on the precipitation type distinction, the precipitation type and its amount changing trend in recent 50 years of the Babao River basin was examined. On average, snowfall accounts for 10.7% in whole year, and mainly happens in March, April, May and October (8.9% in whole year). In the context of climate warming, the annual precipitation and rainfall increasing significantly while the annual snowfall decreased slightly. Furthermore, on the perspective of monthly changes, rainfall amounts of May and August enhanced significantly while snowfall amount decreased significantly in June and September. The above conclusions indicated the warming climate also changed the precipitation pattern in the Babao River basin which would likely cause drought in the spring season and bring challenge to the local agriculture.

How to cite: Wang, G. and Zhang, F.: Types and amounts of the precipitation changes in recent 50 years of the Babao River basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7886, https://doi.org/10.5194/egusphere-egu21-7886, 2021.

This study investigates the long-term variations of local land atmosphere coupling (LoCo) over Tibetan Plateau (TP) by applying a mixing diagram to the observational data at six stations over TP and ERA5 and the possible influence of Southern Asian monsoon. The result indicates that the monthly-mean daily variation in T_2m, q_2m, H_sfc, and LE_sfc at Nyingchi, Nagqu, Nam Co, Qomolangma, Ngari, and Muztagata in ERA5 are close to those in observational data. Comparison of mixing diagram analysis using the monthly-mean variables of ERA5 and the observational data indicates ERA5 could provide reliable information of LoCo at six stations. The relationships between H_sfc and daytime PBLH, and the variations of LCL deficit at six stations are different due to the differences in the soil states. The long-term variations in the PBL energy budgets, mean daytime PBLH, and LCL deficits at 31^◦N and 90^◦E show clear annual variations and have a close relationship between Southern Asian monsoon. The possible influence of the Southern Asian monsoon is also discussed in terms of the relationship between the Webster-Yang index and the PBL energy budgets, mean PBLH and mean LCL over TP.

How to cite: Sun, G., Hu, Z., Ma, Y., Xie, Z., Wei, W., and Yang, S.: Long-term variation of characteristics of local land atmosphere coupling over TP and the possible influence of Southern Asian Monsoon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5391, https://doi.org/10.5194/egusphere-egu21-5391, 2021.