Evaluation and Analysis of Artificial Rainfall Enhancement in Erhai Basin on Southeastern Edge of Qinghai-Tibet Plateau
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Abstract:
With global warming, the occurrence of extreme weather and climate events, coupled with the rapid development of the economy and society, the problem of water resource shortages in Erhai Lake is becoming increasingly serious. To increase precipitation in the Erhai Lake basin, the meteorological department often carries out artificial rainfall enhancement operations and establishes artificial rainfall enhancement test areas in the Erhai Lake basin to conduct artificial rainfall enhancement effect evaluation research, so as to improve the ability of artificial rainfall enhancement operations. According to the weather situation of the rainfall enhancement operation day, this paper selects 819 daily precipitation data points of the test area and the contrast area in the Erhai Lake basin from 2005 to 2014 (November to February in winter and June to September in summer), and 79 rainfall enhancement operation data points from 2015 to 2020. The artificial rainfall enhancement operations in the Erhai Lake basin are subject to statistical and physical tests, and the following conclusions are drawn. (1) The statistical effect test of the artificial rainfall enhancement operations in the Erhai Lake basin is carried out by using the regional regression numerical simulation evaluation programme. The rainfall enhancement efficiency of stratus and mixed cloud is 16.57% and 20.09% respectively, and passes the significance test at the significance level α≤0.05. (2) The physical examination of the rainfall enhancement effect of the stratus cloud precipitation on 31 January 2020 and the mixed cloud precipitation on 13 August 2020 is conducted by using the new generation of weather radar. The results show that the maximum echo intensity and the average vertical integral liquid water content (VIL) of the stratus cloud target cloud body in the experimental area decreases slightly after the operation, and the echo top height changes little. The maximum echo intensity, the average VIL and the echo top height of the mixed cloud target cloud body increase rapidly. The ground rainfall intensity is significantly enhanced after the two types of rainfall enhancement operations. (3) The physical examination of the above two processes is conducted by using the laser raindrop spectrometer. The results show that the rainfall intensity and the number concentration of the stratus cloud and the mixed cloud rainfall enhancement operations in the experimental area begin to increase about 10-15 minutes after the operation. The diameter of the maximum number concentration changes from 0.437 mm to 0.562 mm, the spectral width increases, and the peak type changes from single peak to bimodal structure. The characteristics of the raindrop spectrum in the contrast area do not change obviously during the same period, indicating that the rainfall enhancement operation intensifies the condensation of water vapour in the cloud and produces more raindrops, and at the same time, it touches and produces larger scale raindrops.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.