北疆春季降水相态转换判识和成因分析  

A Forecast Analysis of Precipitation Phase Transformation and Rainfall Intensity in Spring over Northern Xinjiang

作　　者：张俊兰 彭军 

机构地区：[1]新疆维吾尔自治区气象台,乌鲁木齐830002 [2]巴音郭楞蒙古自治州气象局,库尔勒841000

出　　处：《高原气象》2017年第4期939-949,共11页Plateau Meteorology

基　　金：中国气象局预报员专项(CMAYBY2016-083);国家科技支撑计划项目(2012BAC23B01)

摘　　要：2014年4月13-15日北疆出现了大范围雨转雪天气和强降雪过程,给当地工农牧业及人民生活造成严重影响。对这次过程,利用天气学诊断方法,分析了其发生发展过程,并得到此次灾害性天气过程中雨雪相态转换和降水强度的预报指标。结果显示:(1)此次天气过程是在中亚低涡两次生成、发展和减弱过程中出现的。(2)中低层温度变化是预报北疆春季降水相态转换的关键因子和指标,中层温度可区分雪和雨夹雪,T_(500)<-25℃、T_(700)<-12℃可判定为雨夹雪转雪;低层温度可区分雨和雨夹雪,T_(850)<-2℃和T_(925)<2℃时雨转雨夹雪,T_(850)<-4.5℃用来判别雨夹雪转雪。(3)春季北疆沿天山一带和天山山区的降水中水汽凝结起主要作用,中低层水汽冷凝结是影响降水强度的重要因子,水汽条件越好、冷空气越强、凝结厚度越厚、持续时间越长,则降水强度越强,水汽冷凝结强度决定了降水强度的大小。A large-scale rain followed by snowand heavy snowprocess happened in northern Xinjiang from 13 to15 April 2014,which has brought serious impact on local agricultural,works and people＇s life. Using the diagnosis method of the weather,the forecast index of phase transformation between rain and snowas well as rainfall intensity was studied. The result shows：（ 1） Change of temperature at middle-lowlevel is the key factor and index to Forecast precipitation phase transformation in spring in Northern Xinjiang.（ 2） Temperature at the middle level is a key factor to distinguish between the snowand sleet. Sleet turning to snowwhen the temperature is less than-25 ℃ on 500 h Pa and less than-12 ℃ on 700 h Pa; Temperature at the lowlevel can distinguish between the rain and sleet,rain turning to sleet in the case of the temperature less than-2 ℃ on 850 h Pa and less than2 ℃ on 925 h Pa. Additionlly,the forecast index of sleet turning to snowwhen the temperature is less than-4. 5 ℃ on 850 h Pa.（ 3） Cooling condensation of water vapor plays an important role on precipitation process in spring over the northern edge of the Northern Xinjiang and the Tianshan mountainous. Cooling condensation of the lower water vapor is an important factor affecting the rainfall intensity. There are more water vapor、stronger cold air、thicker condensation which can induce longer and stronger rainfall. The rainfall intensity is decided by the cooling condensation of water vapor.

关 键 词：降水相态 降水强度 中低层温度 水汽冷凝结 

分 类 号：P456.7[天文地球—大气科学及气象学]