Abstract
Local precipitation variations in the context of global warming are a hot topic in the climate change research community. Using daily precipitation data spanning from 1984 to 2014 from 25 meteorological stations, the spatiotemporal variations of precipitation were analyzed for the southern part of Heihe River Basin (HRB), which is the second-largest inland river basin in Northwest China. Linear trend analysis, empirical orthogonal function (EOF) analysis, the Mann–Kendall test, and the moving t-test were employed in the study. Results showed that the regional annual precipitation exhibited an increasing trend with a slope of 13.1 mm per decade from 1984 to 2014. The increasing trend was detected at 21 sites and the first EOF illustrating the regional increasing trend explained 51.8% of the total variance. The increasing trend of annual precipitation was mainly due to an increase in autumn precipitation, while summer precipitation exhibited a weak declining trend and spring–winter precipitation remained unchanged. Moreover, the increasing precipitation trend was mainly caused by an abrupt increase around 1997, when the global warming hiatus occurred. Through 1997, the atmospheric circulation and physical structure, such as vertical upward motion, vapor transmission, and its convergence changed to be more favorable for precipitation in autumn, but unfavorable for precipitation in summer in the HRB.
Highlights
As the only source of water in the inland watershed of an arid area, precipitation determines the categories and spatial distribution of natural ecosystem, and plays a crucial role in agricultural yield, economic development, and societal statues [1,2]
This study disclosed the spatiotemporal characters of precipitation variations in the southern part of the Heihe River Basin (HRB) from 1984 to 2014, and analyzed the potential physical mechanisms leading to the precipitation changes
The several years of high-resolution (3–5 km) simulations with Weather Research and Forecast (WRF) model show that the western part of the Qilian Mountain has less precipitation than the southeastern part [21,22] It is noted that simulated precipitation is significantly larger than the station measurements in the mountainous area due to the high sensitivity of the micro-physical parameters of the WRF model to complex terrain [22]
Summary
As the only source of water in the inland watershed of an arid area, precipitation determines the categories and spatial distribution of natural ecosystem, and plays a crucial role in agricultural yield, economic development, and societal statues [1,2]. The Heihe River, which is located in arid and semi-arid regions of Northwest China, is the second-largest inland river of China, with a length of 821 km and drainage area of 130,000 km. There is the Qilian Mountains, with remarkable vertical zonality. It is the water source of HRB and the elevation of the area ranges from 2000 m to 5500 m. There is Hexi Corridor, where the elevation decreases from 2000 m to 1000 m. It is located between the Qilian Mountains and the Beishan Mountains.
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