Changes in snowfall fraction and the driving factors across headwaters of the Yellow River Basin based on multi-source data
The headwaters of the Yellow River Basin (HYRB),located in the northeastern part of the Qinghai-Xizang (Tibet) Plateau,serves as the main source of water and is highly sensitive to climate change. However,under the background of climate warming,understanding of shifts in precipitation types and the underlying causes remains limited. This study,focusing on this important scientific issue,utilized a parameterized model of wet-bulb temperature (a precipitation pattern recognition model using surface air temperature,surface pressure,relative humidity and elevation) to differentiate precipitation types across the HYRB from 1980 to 2015. Addi-tionally,we analyzed changes in the annual mean precipitation,rainfall,snowfall and snowfall fraction during this period using the Mann-Kendall test and the Sen' slope estimator. We especially focused on changes in snow-fall fraction (SF,defined as snowfall/total precipitation) and analyzed spatial distribution of changes of SF. In order to reduce uncertainty in the differentiation of precipitation patterns by a single product,the analysis is based on weather station observations and multi-source high-resolution meteorological datasets,including the China Meteorological Forcing Dataset (CMFD),the ECWMF ERA5-Land (ERA5-Land),and the Multi-Source Weather (MSWX). Further,we used the partial correlation analysis to conduct mechanism analyses of the underlying causes of long-term changes in SF in terms of both meteorological and circulation factors,includ-ing surface air temperature,relative humidity,precipitation,surface pressure,westerly winds,Indian mon-soon,East Asian summer monsoon and ENSO. The results indicate that:(1) Annual mean SF exhibited signifi-cant (P<0.05) decreasing trends (0.002 a-1),because there was a decrease in snowfall,but rainfall increased significantly. The precipitation pattern shifted to rainfall. (2) Regionally,the percentage of grids with signifi-cant (P<0.05) decreasing trends in SF to the total grids of the HYRB was 98.31％ for the ERA5-Land,96.87％ for the MSWX,and 67.62％ for the CMFD. In particular,the west-central part of the HYRB exhibited a more rapid decline in SF,with Maduo (Madoi County) and Dari (Darlag County) experiencing the largest decreasing trends. (3) The three gridded datasets differed in their ability to capture the spatial variability of snowfall. Spe-cifically,CMFD showed substantial spatial variation and presented well to spatial differences in trend of SF. MSWX was the second best,while ERA5-Land displayed a notable spatial homogeneity. (4) The annual mean SF was highly correlated with annual mean air temperature and precipitation (P<0.05),with correlation coeffi-cients r of-0.42 and-0.48. Moreover,westerlies also had a notable influence (r=-0.31,P=0.07). Other fac-tors had less effect on SF. These findings enhance our knowledge of the effects of climate warming on hydrome-teorology. The identified trends and correlations offer theoretical support for the management of regional water resources in the Yellow River Basin and have important implications for water resources management across the HYRB.
headwaters of the Yellow River Basinprecipitation patternsparameterized model of wet-bulb temperaturesnowfall fractionclimate change
宋怡铭、徐世琴、余钟波、董宁澎
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西北师范大学地理与环境科学学院,甘肃兰州 730070
Hydrology,Agriculture and Land Observation Laboratory,Division of Biological and Environmental Science and Engineering,King Abdullah University of Science and Technology,Thuwal 23955-6900,Saudi Arabia
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