河南省春季层状云系降水的空中水资源特征分析

A Study of the Feature of Water Resources in Spring Precipitating Stratiform Clouds in Henan Province

利用ARPS中尺度数值模式对河南省2005年3月20—21日层状云系降水过程中的云水资源特征进行了模拟分析,模式主要计算了水汽收支状况、云中水分的微物理转化和降水效率等。结果表明,充沛的水汽输送为云系的形成和发展提供了有利条件,河南省域的水汽收入主要是水平流入,地表蒸发的贡献相对较小。河南南边界和西边界是此次降水过程水汽的主要水平流入边界,东边界和北边界是水汽的主要水平流出边界,较强的流入高度在2km附近。云系呈明显的垂直分层结构,平均0℃层在2.5km高度附近。6km高度以上的高云为冰云,2.5~6km高度之间的中云为冰水混合云,2.5km以下的低云为水云,符合“播撒-供给”云结构。雪和霰主要在4km高度左右生长,雨水主要在2.5km高度左右的0℃层附近生长。全省小时降水效率和地面小时降水量的时间变化趋势较为一致,但明显滞后于水汽流入率的时间变化。在降水较强时段,河南省域的小时降水效率为20%~30%。降水效率的分布形势与累计降水较为一致,河南南部较高、北部较低。

Abstract： The feature of water resources in precipitating stratiform clouds during March 20-21, 2005 in Henan Province was studied using ARPS model. Vapor inflow and outflow, microphysical conversion of water substance in clouds, and precipitation efficiency were simulated. The model simulation declared that plentiful vapor inflow provided a favorable condition for the formation and development of clouds. The inflow of vapor in the Henan region was mostly horizontal with weak contribution from surface evaporation. The main vapor inflow exists in the southern and western sides of Henan with the strongest inflow at about the height of 2 kin, whereas the eastern and northern sides are main vapor outflow. The average height of 0℃ layer is about 2.5km. The clouds have a distinct vertically-layered structure with ice cloud above 6 km, water-ice mixed cloud between 2.5-6kin, and liquid cloud below 2.5km, which accords with the ＂seeder-feeder＂ cloud structure. The horizontal flow of hydrometeor was weaker compared with the vapor flow. The growth of precipitating ice particles mainly occurs at about the height of 4km, and that of rain droplets at about the height of 2.5km, where is near the zero temperature level. The temporal change of regional hourly precipitation efficiency is consistent with surface hourly precipitation with a distinct lag behind the vapor inflow. During strong precipitation, regional hourly precipitation efficiency is 20% -30%. The distribution of regional precipitation efficiency is consistent with total precipitation with higher value in the southern Henan and lower value in the north.