The Source Area of the Yellow River is located in the northeastern part of the Qinghai-Xizang Pla-teau,and the meteorological stations are sparsely distributed in this basin,the study of the applicability of vari-ous precipitation data products has an important values in promoting the hydrological modeling in the basin.Based on the China Meteorological Assimilation Datasets for SWAT model Version1.1(CMADS V1.1),the Tropical Rainfall Measurement Mission(TRMM)precipitation datasets(3B42 Version7)and the Soil and Water Assessment Tool(SWAT)driven by these precipitation data,respectively,and the SWAT-CUP(SWAT Calibra-tion and Uncertainty Program)and SUFI-2(Sequential Uncertainty Fitting2)algorithm 27 sensitivity parameters were rate in simulating the variation of multi-year monthly average runoff,the simulated results were compared with the observations to evaluate the accuracy of CMADS and TRMM 3B42 precipitation data products and the applicability of SWAT model were evaluated in the Source Area of the Yellow River source area.The results show that:(1)The distribution of all three precipitation datasets showed an increasing trend from the west to the east,and TRMM 3B42 was in better agreement with the measured precipitation than CMADS data set in terms of annual and monthly variation.(2)The sensitivity analysis of the parameters showed that the sensitivity degree of SCS(Soil Conservation Service)runoff curve number,groundwater lagging coefficient,and soil evaporation compensation coefficient were stronger than that of the others.(3)The simulated runoff by using the CMADS and TRMM 3B42 precipitation datasets had better results than that by using the measured precipitation data,with the correlation coefficients R2 of 0.93,0.92 and 0.88 for the rate period at the three hydrological stations,re-spectively,while the results of the TRMM 3B42 simulation were the next best,with the coefficients of correla-tion(R)of the rate-period and validation-period of above 0.80,and the Nash-Sutcliffe efficiency coefficient(NSE)of the simulations is above 0.50.This research demonstrates the applicability of CMADS datasets and SWAT model for runoff simulation in high-altitude areas with complex landscape types and sensitive to climate change,and provides a replacement solution for improving the hydrological models in areas where there are sparely meteorological stations.

The Yarlung Zangbo Grand Canyon region （referred to as the YGC）， located in the southeast Qinghai-Xizang Plateau， is the main channel of the warm and humid air transported from the India Ocean to the Qinghai-Xizang Plateau （referred to as the QXP）， and it plays an important role in the water and energy cycle of the QXP.In order to explore the influences of the different horizontal water vapor transport on the water & heat exchanges flux， the water vapor intensity over the YGC from May 20， to July 9， 2013， was divided into three levels： strong， weak， and very weak based on the ECMWF Re-Analyses version5 data.And the fifth-generation public land model （Community Land Model version 5.0， CLM5.0） was deployed to simulate the impact of the horizontal water vapor transport on the YGC-atmospheric water and heat exchanges.The results show that the south （east） boundary of the YGC is the main input （output） boundary of water vapor， and the YGC valley over the south of the YGC is a strong water vapor transport belt.The YGC-atmospheric water & heat exchanges fluxes simulated by CLM5.0 has large errors compared to the actual measurements， the CLM5.0 simulated near-surface water & heat exchanges fluxes over the YGC have a high accuracy by optimizing the thermal roughness length （Z0h） parameterization schemes replacing the default soil attribute data-set.Compared with the simulations by using the CLM5.0 default parameterization scheme， the one developed by Zeng and Dickinson （1998）.（Z98 scheme for short） has the lowest errors， the root mean square error of the near-surface sensible heat flux at the wheat station and the grassland station decreased by 18.2% and 10.9%， respectively.The results of regional simulation show that the general distribution of the near-surface latent heat flux （LE） over the YGC is high in the southeast and low in the northwest， while the near-surface sensible heat flux （H） is the opposite.As the water vapor transport intensity decreasing， the area with high near-surface latent heat flux extends to the northwest， while the near-surface sensible heat flux （H） is the opposite.The H in the high-altitude ice and snow-covered area maintains a low value， while the LE is the opposite.During the entire experimental period， the precipitation was as high as 59% over the YGC， which is abundant precipitation.The near-surface effective energy is mainly transported to the atmosphere in a form of latent heat under different horizontal water vapor transport conditions.The near-surface sensible heat transport is the weakest in the strong water vapor transport belt under the condition of strong horizontal water vapor transport.The regional daily average value of the H is only -1.80 W∙m-2 by using the Z98 scheme， while the LE is greater than 70.0 W∙m-2.When the water vapor maintains a high-value range over the Grand Canyon area， the near-surface net radiation decreases， but the near-surface net radiation is still mainly consumed by the latent heat.The warming effect of the water vapor on the local atmosphere resulted in the difference of ground-atmospheric temperature decreases， and the near-surface sensible heat is significantly inhibited.The results of this study have a certain reference value for understanding the land surface process over the YGC and its response to horizontal water vapor transport.

Permafrost have a critical impact on the infrastructure construction， hydrology and ecology in the cold region.Under the background of global warming， it is of great significance to explore soil freeze-thawing cycle over the Western China.Based on the natural geographical and permafrost characteristics， the western region of China is divided into four sub-regions as the study region of this investigation.The ERA-5 surface temperature， soil volumetric water content and monthly air temperature data from January 1981 to June 2020 are to be deployed in analyzing the spatio-temporal distribution of soil freeze-thawing status， the active layer thickness and maximum freezing depth over the western China in the past 40 years.the correlationship between variables of freeze-thawing cycles and air temperature and altitude are discussed.The results show that： the spatio-temporal distribution of the start date of freezing and thawing has the characteristics of delayed freezing and early thawing from high-altitude areas to low-altitude areas over the western region.The high-altitude northern Tibetan plateau freezes the earliest， thaws the last， and freezes the longest.The sporadic areas on the Kunlun Mountains can last for more than 300 days.The Tarim Basin in the west-northwest with low altitude and low soil moisture content freezes the latest， melts the earliest， and lasts the longest.The melting in the Taklimakan Desert can last for more than 280 days.The thickness of the permafrost active layer is basically more than 2.0 m， only the area near the Karakoram Mountains has a large area with a thickness of less than 2 meters.the seasonal frozen soil of the Qinghai-Tibet Plateau has the largest freezing depth， and the thickness can reach more than two meters， and the Tarim Basin shows a shallowest freezing depth， and the thickness is less than 0.6 m.The start date of freezing was delayed over the western region， and the start date of thawing was advanced.The date of start freezing and the date of completely frozen increased at a rate of 0.089 d·a-1and 0.061 d·a-1.The date of start thawing and the date of completely thawed decreased at a rate of 0.102 d·a-1 and 0.156 d·a-1.When the freezing trend is rising and the thawing trend is declining， the duration of completely thawed increased by about 12 days at a rate of 0.256 d·a-1， and the duration of completely frozen is shortened by about 11 days with a rate of 0.164 d·a-1， during the study period， the start date of completely thawed was mutated in 1996.The date of start freezing and the duration of completely thawed were abrupted changed in 1997.The overall change trend of the start date of the freezing and thawing is the same over the western region， but there are locally slight differences.The duration of start freezing and completely frozen of the Loess Plateau decreased the fastest at the rate of 0.166 d·a-1 and 0.405 d·a-1.The duration of start freezing and the duration of completely frozen were shortened by around 7 and 16 days.The trends in the duration of completely melt period in all four regions showed an upward trend.However， the duration of completely frozen rises rapidly at a rate of 0.435 d·a-1 over the Loess Plateau， and increase about 17 days during 1981 -2020.There is a significant correlation between the start dates of freezing and thawing and the annual average temperature and altitude.The correlation between the annual average temperature and all freeze-thaw times exceeded 0.79， and the negative correlation between the date of completely thawed and the annual average temperature was as high as 0.963.The start date of freezing was delayed by 2.03 days per 1.0 ℃ increase， the start date of complete freezing was delayed by 2.12 days， and the start dates of completely thawed and frozen were advanced by 5.10 and 5.17 days， respectively.The start dates of freezing and completely frozen are advanced by 6.1 days and 4.5 days per 1000 m rise in altitude， respectively， and the start dates of thawing and freezing are delayed by 14.4 days and 19.9 days， respectively.This research clarifies the situation of soil freezing and thawing and its variation in the past years over the western China， and provides a scientific supports for the ecological system and infrastructure construction over the western region.

Precipitation has a significant influence on the topsoil moisture and further impacts the land-atmospheric water and heat exchange process over the Yarlung Zangbo Grand Canyon region (YGC) where exhibits one of the highest frequencies of convective activity in China. The simulated performance of the Community Land Model version 5.0 (CLM5.0) on turbulent fluxes under seven roughness heights for heat transfer (Z 0h ) schemes at Motuo and Pailong stations over the YGC was evaluated. The results indicate that the CLM5.0 significantly overestimates the surface sensible heat flux (H) while the simulation performance of surface latent heat flux (LE) is better than H. By comparing and analyzing the simulation results, the Z 0h schemes suitable for the YGC are selected optimally. The Zeng et al. (J. Hydrometeorol., 2012, 13, 1359–1370) scheme (Z12) is more suitable for the simulations of H, with the simulated RMSE of H at Motuo and Pailong stations on typical sunny days being only 21.63 and 15.13 W m−2, respectively, 81.51% and 76.96% lower than the original Z 0h scheme of CLM5.0. The Garratt, J., R and Francey, R., J (Boundary. Layer. Meteorol., 1978, 15, 399–421) scheme (G78) is more suitable for simulating LE in the YGC. The simulated BIAS and RMSE of LE at Motuo station were 9.80% and 21.90% lower than that under the default scheme of CLM5.0 on typical cloudy days. In addition, except for the G78 and CLM5.0 default scheme, the Z 0h under the other schemes showed obvious diurnal variation characteristics, and H was positively sensitive to Z 0h , while LE was the opposite. Consequently, the optimal Z 0h schemes are of great application value for further comparative analysis of the water and heat exchange process between the Grand Canyon land surface and the atmosphere, to better reveal the mechanism of land-atmosphere interactions in the YGC.

The source area of the Yellow River (SAYR) is one of the world´s largest wetlands containing the greatest diversity of high altitude marshlands. For this reason, its response to climate change is extremely significant. As revealed by different studies, the response of hydrological processes to global warming results in high uncertainties and complexities in the water cycle of the SAYR. Thus, understanding and projecting future runoff changes in this region has become increasingly important. In the present investigation, we used runoff and meteorological data of the SAYR from 1976 to 2014 (historical period). In addition, Digital Elevation Model (DEM), land-use, and soil data for the period 1976 to 2100 were used considering three future SSPs (Shared Socioeconomic Paths) scenarios of 8 models selected from the Coupled Model Intercomparison Project Phase 6 (CMIP6). The Soil and Water Assessment Tool (SWAT) was used to simulate, project, and analyze potential variations and future runoff of the main hydrological stations (Jimai, Maqu, and Tangnaihai) located in the SAYR. The results showed that: 1) The SWAT model displayed good applicability in historical runoff simulation in the SAYR. A small runoff simulation uncertainty was observed as the simulated value was close to the measured value. 2) Under three different 2021–2100 SSPs scenarios, the yearly discharge of the three hydrological stations located in the SAYR showed an increasing trend with respect to the historical period. Future runoff is mainly affected by precipitation. 3) We compared the 1976–2014 average annual runoff with projected values for the periods 2021–2060 and 2061–2100. With respect to 2021–2060, the lowest and highest increases occurred at Tangnaihai and Maqu Stations in the emission scenarios without (SSP585) and with mitigation (SSP126), respectively. However, the highest and lowest increments at Jimai Station were observed in the intermediate emission (SSP245) and SSP126 scenarios, respectively. Moreover, in 2061–2100, the Maqu and Tangnaihai Stations showed the lowest and highest increments in the SSP585 and SSP245 scenarios, correspondingly. In Jimai Station, the lowest increment occurred in SSP126. The yearly average discharge in the near future will be smaller than that in the far future. Overall, this study provides scientific understanding of future hydrological responses to climate changes in the alpine area. This information can also be of help in the selection of actions for macro-control, planning, and management of water resources, and the protection of wetlands in the SAYR.

The Source Region of the Three-River （SRTR） lies in the hinterland of the Qinghai-Xizang （Tibetan） Plateau （QXP） and is one of the sensitive regions to climate change in East Asia.It is of great significance to study the distribution， transport， and budget of water vapor for understanding the characteristics of the regional precipitation.This research is based on the ERA5 reanalysis data of the European Centre for Medium-Range Weather Forecasts （ECMWF） from 1980 to 2019， combined with the data of 9 radiosonde stations in the National Meteorological Data Center from 1981 to 2010.The temporal and spatial variation characteristics of water vapor distribution， water vapor transport flux and budget of each boundary over the SRTR and its surrounding areas are analyzed.The results show that there are significant differences in the spatial distribution of water vapor content， which presents a high value region in the southeastern QXP and a low value region in the northwest of the QXP.The distribution and value of water vapor content are different in four seasons， which exhibit the largest in summer， followed by autumn and spring， and the least in winter.The annual cycle of water vapor content manifests the single peak over the SRTR and the Brahmaputra River basin.Water vapor is mainly concentrated in June to August and its maximum appears in July with a value of 41.6 mm.The inter-annual variation shows an increasing trend with a rate of 0.4 mm·（10a）-1.The Arabian Sea and the Bay of Bengal are the main sources of water vapor over the SRTR， followed by the western airflow from the middle latitude and the northwestern airflow.Three kinds of airflows form obvious convergence of water vapor transport flux over the Brahmaputra Grand Canyon.There are seasonal discrepancies in the intensity of water vapor transport.Among the water vapor import boundaries， the western boundary has the largest import （815.3×106 kg·s-1）， followed by the southern boundary （724.9×106 kg·s-1） and the seasonal variations of the two boundaries are significant.The northern boundary has less import （317.9×106 kg·s-1）， while the eastern boundary is the export boundary of water vapor flux， and the maximum water vapor export is in September with a value of 140.5×106 kg·s-1.The net water vapor import is greater than the export， thus the water vapor flux is in surplus， which is about to affect the variations of precipitation and the regional water cycle over the SRTR.

Precipitation is one of the most important meteorological factors affecting the water cycle and ecological system over the Source Region of the Three-River (SRTR), where the Yangtze River, Yellow River, and Lantsang River originated. The characteristics of water vapor transport and budget in annual and summer over the SRTR are analyzed using monthly observational and reanalysis datasets during 1980-2019. The linkage between water vapor transport and summer precipitation is also explored in this study. The results show that the Global Precipitation Climatology Project (GPCP) data are in agreement with the measured precipitation well. The SRTR is a sink region for water vapor, where the water vapor content shows an increasing trend with a rate of 0.2 mm/10a in annual and 0.3 mm/10a in summer. The water vapor mainly flows into the SRTR from the lower (521.2×106 kg s−1) and the middle (195.7×106 kg s−1) layers of the southern boundary in summer, while it exports from the middle (208.1×106 kg s−1) layer of the eastern boundary. The abnormal wind convergence and the low-pressure system, combining with the effects of the Western Pacific Subtropical High and the Mongolian High, provide conditions for the transport of water vapor and precipitation over the SRTR. A close relationship is found between water vapor flux and precipitation from the Singular Value Decomposition (SVD) analysis. The Brahmaputra River basin is the key region of water vapor transport over the SRTR, which contributes to further understanding the mechanisms of water vapor transport and the regional water cycle.

黄河源区是黄河流域的重要组成部分，其径流变化影响着整个流域的水资源和生态系统安全。本文利用1976—2014年黄河源区径流、气象、数字高程模型DEM（Digital Elevation Model）、土地利用、土壤以及第六次国际耦合模式比较计划CMIP6（6thCoupled Model Inter-comparison Project）中8个模式的3个未来情景（SSP126、SSP245和SSP585）气象数据，基于SWAT（Soil and Water Assessment Tool）水文模型，对黄河源区主要水文站的径流进行了模拟、未来预估和变化分析。研究表明：（1）SWAT模型对黄河源区历史径流模拟的适用性较好，径流模拟的不确定性较小，模拟值较接近于实测值。（2）参数敏感性分析表明27个与水文有关的参数都对径流模拟有一定的影响。其中，土壤蒸发补偿因子、湿润条件II下SCS（Soil Conservation Sevice）径流曲线数、浅层地下水径流系数的敏感性较强，径流受陆面蒸散发、下垫面和降水影响较大。（3）降水是影响未来径流的主要因素。在SSP126和SSP245两种未来情景下，吉迈、玛曲和唐乃亥3个水文站在2021—2100年的两个时期（2021—2060年和2061—2100年）年均流量均呈增加趋势；而在SSP585情景下，2021—2060年呈增加趋势，2061—2100年则呈减少趋势。相对于1976—2014年，未来近期（2021—2060年）唐乃亥和玛曲站年均流量在SSP585情景下增加幅度最低，SSP126情景下增加幅度最高；吉迈站在SSP245情景下增加幅度最高，SSP126情景下增加幅度最低；未来远期（2061—2100年）3个水文站除了吉迈站是在SSP126情景下增加幅度最低外，其余均是在SSP585情景下增加幅度最低，SSP245情景下增加幅度最高。研究结果可为黄河流域水资源管理、防洪蓄水和生态环境保护等提供科学依据与理论支撑。

为研究成都地区相对湿度的变化特征及中尺度数值模式不同陆面过程方案对该地区相对湿度的模拟能力,利用成都市2014年地面观测资料和NCEP再分析资料,通过不同时间尺度统计分析和数值模拟试验的方法,对比分析成都相对湿度特征及不同陆面过程方案模拟效果.结论 表明:成都市平均相对湿度较高,主要集中在85％～100％;相对湿度季节变化中,秋季相对湿度最大,夏、冬季次之,春季最小;日变化中白天相对湿度较小,夜间较大;四季中相对湿度日变化大致相似,但幅度不同,春季日变化最为显著,冬、夏次之,秋季最小;3种常用的陆面过程参数化方案对成都城市下垫面相对湿度的变化趋势模拟较好,但在极值模拟上有所差异,通过参数评估,5Layer方案对城市下垫面相对湿度模拟效果的最好.