青藏高原东南缘洱海流域人工增雨效果评估

Evaluation and Analysis of Artificial Rainfall Enhancement in Erhai Basin on Southeastern Edge of Qinghai-Tibet Plateau

摘要:

采用区域回归数值模拟评价方案对2005—2020年洱海流域火箭人工增雨效果进行统计检验，得出洱海流域层云、混合云增雨效率分别为16.57 %和20.09 %。利用新一代天气雷达和激光雨滴谱仪对2020年1月31日层云降水和8月13日混合云降水进行增雨效果物理检验发现：作业后试验区层云目标云体雷达最大回波强度和平均垂直积分液态水含量（VIL）略有降低，回波顶高变化不大，混合云目标云体最大回波强度、平均VIL和回波顶高均出现跃增，两种类型增雨作业后地面降雨强度均显著增强。雨滴谱特征表明，试验区层云和混合云雨强和雨滴数浓度在作业后10～15 min开始增加，最大数浓度所在直径由0.437 mm增加到0.562 mm，雨滴谱的谱宽增加，峰型由单峰变为双峰结构。

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.