近30a山西不同相态降水的统计特征及概念模型

利用山西省1981~2010年108站的地面降水观测数据,以降水量≥0.1 mm的日数为指标,对山西108个县市不同相态降水的时空分布特征进行了分析,结果表明:五寨(山西西北部)和陵川(山西东南部)平均降雨日数、平均降雪日数、平均雨夹雪日数都位于全省之首;30 a间山西的降雨日数和降雪日数分别以3.333 d/10 a和1.529 d/10 a的趋势减少,而雨夹雪日数则以0.34 d/10 a的趋势增多;山西区域降雪和降雨日数变化趋势的空间分布都具有西部减少趋势高于东部的特征,雨夹雪日数变化趋势的空间分布则具有东部增多趋势高于西部增多趋势的特征;朔州和忻州西部是降雪日数减少趋势最强的区域,运城是降雨日数减少趋势最强的区域,晋城是雨夹雪日数增多趋势最强的区域。应用328个多相态降水过程资料和NCEP再分析资料进行统计分析,结果表明:冷空气侵入导致中低空温度下降,0℃层高度降低是降水相态发生变化的主要原因;-3℃和0℃是山西中南部降水相态转变时850 hPa和925 hPa的临界值;3.5℃则是山西北部和高海拔地区降水相态发生转变时850 hPa温度的临界值;西北路冷空气侵入多相态降水过程,地面冷锋是降水相态的分界线,东路冷空气侵入多相态降水过程,低空切变线则是降水相态的分界线。

The Statistical Characteristics and Conceptual Model of Different Phase Precipitation in Recent 30 a in Shanxi Province

Based on the ground precipitation data of 108 stations from 1981 to 2010 in Shanxi,the temporal and spatial distribution characteristics of different phase precipitation in 108 counties and cities in Shanxi were analyzed.Results show that the average days of rainfall,snowfall and sleet in Wuzhai（in the northwest of Shanxi）and Lingchuan（in the southeast of Shanxi）were most.The rainfall days and snowfall days decreased with the tendency of 3.333 d/10 a and 1.529 d/10 a in recent 30 a in Shanxi,respectively,while the sleet days increased with the tendency of 0.34 d/10 a.The dcreasing trend for both snowfall and rainfall days was higher in the west region than that in the east Shanxi,but for sleet days,the increasing trend was higher in east Shanxi than that in the west region. The decreasing trend of snowfall days was maximum in Shuozhou and the east of Xinzhou,and Yuncheng was the area where the rainfall days’decreasing trend was maximum,Jincheng was the area where the sleet days’increasing trend was strongest.The statistical anal-ysis was made by using 328 multi-phase precipitation processes data and the NCEP reanalyzed data,and the results show that the in-vasion of cold air resulted in the mid-low level’s temperature dropping,and the height of 0 ℃layer descending,which was the main cause of precipitation phase change.The critical temperature that made precipitation phase transition in the south-center of Shanxi on the level of 850 hPa and 925 hP were -3 ℃ and 0 ℃,respectively.While 3.5 ℃ is the critical temperature on 850 hPa that made precipitation phase transition in the north and high elevation area of Shanxi.In the processes that the northwest cold air intruded multi-phase precipitation,the ground cold front was the boundary of the precipitation phase,while in the process that the east cold air in-truded multi-phase precipitation,the low level shear line was the boundary of the precipitation phase.