“4.17”森林灭火飞机增雨过程分析

Analysis of Artificial Rainfall Effects Aircraft on Forest Fire Fighting on April 17^(th)

为了研究飞机人工增雨工作在森林灭火等应急气象服务中的特点和规律,利用2011年4月17日在秦皇岛抚宁地区森林大火上空进行的一次人工增雨作业所取得的云物理资料,结合适时天气、卫星、雷达等资料,分析了降水过程的天气背景条件、催化前后云中微物理量的变化。结果表明,催化后云体明显发展,云粒子含水量明显增大,云粒子浓度约增长30%～50%,粒子谱变宽,云中冰晶浓度和降水粒子浓度增加。火场及附近地区普遍降雨0.3～5.0mm,对灭火起到了重要作用。影响地面降雨量的主要因素:(1)西风槽系统弱,且偏北,使火区云带狭窄;(2)前期相对湿度低,云层中含水量低,云粒子最大含水量1.318g/m3;(3)高层云下部的层积云较弱,两云之间存在夹层,影响降水粒子的增长。

In order to get the characteristics and regulation of aircraft artificial rainfall work in emergency meteorological services,such as the forest fire fighting,background weather conditions of precipitation process and changes of in-cloud microphysical parameters after the feeding operation were analyzed by using data of cloud physics obtained from one artificial rainfall operation over the forest fire in Funing Region,Qinhuangdao,on April 17th,combined with data of weather,satellite and radar.The result showed that after the operation,the cloud body had a significant development with a increasing of cloud droplet water content.Cloud droplet concentration increased by approximately 30%-50%.Both the ice crystal concentration in the central part of cloud and precipitation particles in cloud showed an obvious increase.Precipitation in areas near the fire spot was 0.3-5.0mm,which was vital for the firefighting.There were mainly 3 reasons which constrained the precipitation amount.Firstly,the weak westerly trough system was in north which narrowed the cloud band over the fire zone.Secondly,the cloud water content was low with a maximum value of 1.318g/m3,so was the relative humidity in the early stage.Last but not the least,the stratocumulus which was under the altostratus was weak and there was a dry layer between these two,which could affect the formation and development of the precipitation particles.