庐山地区层状云和对流云降水特征对比分析

Characteristics Comparison Analysis of Stratiform Cloud and Convective Cloud Precipitation in Lushan

根据Parsivel激光雨滴谱仪在庐山高海拔观测场获取的2011年降水资料,结合宏观特征量、雨滴谱资料和雷达图像资料,将降水划分为对流云降水和层状云降水,选取了12次典型降水过程。对两类云降水的6种特征直径、各档雨滴对降水参量的贡献、降水微物理参量的演变等进行了分析,并利用M-P分布和Gamma分布对两类云降水雨滴谱进行拟合,对拟合参数以及拟合效果进行了分析。结果表明:两类云降水微物理特征有着本质的区别,层状云降水谱宽相对较窄,参量随时间变化比较平缓,直径不超过1 mm的小滴对降水贡献最大;对流云降水谱宽相对较宽,出现了直径接近10 mm的大滴,参量起伏较大,对数密度贡献很小的大滴对雨强、含水量贡献却比较大。从拟合效果检验来看,层状云降水拟合时的M-P曲线在大部分区段比Gamma曲线更接近实测雨滴谱曲线;对流云降水拟合时的Gamma分布曲线与实际雨滴谱分布曲线整体吻合程度较高。M-P分布和Gamma分布两种拟合方法都适用于层状云降水,对流云降水雨滴谱拟合时Gamma拟合效果优于M-P拟合效果。

The 12 typical rain processes measured by Parsivel optical disdrometer in Lushan in 2011 are selected and divided into stratiform and convective types according to the raindrop spectrum as well as the macroscopical characteristics and the radar images. The six characteristic diameters and the contribu-tion of each raindrop to precipitation and the change of microphysical parameters with time are analyzed, and the M-P distribution and Gamma distribution are used to fit the features of average raindrop spec-trum of the two types of precipitation and the fitting results are also analyzed soon after. The results show that stratiform rain and convective rain have great differences. The parameters of stratiform rain with nar-row spectral width change gently over time and the raindrops less than 1 mm dominates the precipitation, however the parameters of convective rain with wide spectral width change significantly over time and the bigger drops with the maximum diameter which is close to 10 mm make a great contribution to rainfall in-tensity and water content despite their small number. Known from the fitting effect,the M-P fitting curve is closer to the measured raindrop spectrum in most segments for stratiform rain and the Gamma fit-ting curve has a higher agreement with the actual distribution spectrum for convective rain,respectively. The M-P distribution and Gamma distribution are both applicable to stratiform rain,but Gamma distri-bution is superior to the other for convective rain.