河南省层状云降水雨滴谱特征分析

Characteristics Analysis of Raindrop Size Distribution for Stratiform Cloud Precipitation in Henan Province

利用2015-2017年河南省层状云降水过程的Parsivel(Partical Size and Velocity)激光雨滴谱观测资料,对层状云降水的雨滴数浓度、含水量、雨滴直径等微物理参量特征及不同尺度的降水粒子对雨强的贡献进行了统计分析,并采用2种拟合方法对层状云降水雨滴谱进行了拟合。结果表明:河南省层状云降水的空间结构不均匀,各微物理参量的变化存在着起伏,雨滴数浓度为10^(2)个/m^(3)量级,个别达到10^(3)个/m^(3),含水量在10^(-2)~10^(-1) g/m^(3),粒子平均直径<0.5 mm左右,统计的不同台站平均最大粒子直径为1~2 mm,雨强平均值不超过1 mm/h。直径为<2 mm的雨滴对雨强的贡献占96.23%,直径小于1 mm的雨滴对数浓度的贡献最大。雨强是由雨滴最大直径、平均直径和数浓度3者共同决定。层状云降水雨滴的谱分布较窄,滴谱曲线比较平滑。降水开始时,谱型为单峰结构;降水处于稳定阶段时,谱型为双峰和单峰相结合的结构。层状云拟合M-P分布和Г分布偏差均出现在直径<1 mm的小雨滴端,对于微小粒子随直径增大而增多导致的曲线弯曲没能表现出来,相对而言Г分布拟合效果明显略优于M-P分布的拟合效果。河南省层状云降水的2种分布形式分别为N(D)=7373.9exp(-3.67D)和N(D)=10492.05D1.62exp(-5.11D)。

Based on the observation data of the OTT Parsivel(Partical Size and Velocity)laser raindrop distribution during stratiform precipitation processes in spring and autumn in Henan Province from 2015 to 2017,the precipitation microstructural parameters such as number density of raindrops,water content,raindrop diameter and the contribution of precipitation particles at different scales to rain intensity are statistically analyzed,and stratiform precipitation spectrum distribution is fitted by the two fitting methods of M-P andГdistribution.Results show that the spatial structures of stratiform precipitation in spring and autumn are uneven,the variation of micro physical parameters are wavelike,raindrop number concentration is 10^(2)/m^(3) with some of them reaching 10^(3)/m^(3),and water content is within 10^(-2)—10^(-1) g/m^(3).The average diameter of raindrop particle is about 0.5 mm,and the average maximum diameter is 1—2 mm.The average rainfall intensity is less than 1 mm/h.The raindrops with diameter under 2 mm make contribution most to rainfall intensity,standing for 96.23%,while the raindrops with diameter smaller than 1 mm contribute most to number density.Rainfall intensity is determined by the maximum diameter,average diameter and number density of raindrops.The raindrop spectrum of stratiform precipitation width is narrow with smooth raindrop spectrum curves.At the beginning of precipitation,the raindrop size distribution presents single peak basically;when the precipitation steps into stable stage,the raindrop size distribution pattern is controlled by the combination of double peaks and single peak.Deviation is found existing in the small raindrop apex with diameter less than 1 mm between the fitting M-P distribution andГdistribution of stratiform clouds.The curvature of the curve caused by the increase in the diameter of the tiny particles is not shown.Relatively speaking,the fitting result ofГdistribution is clearly better than that of the M-P distribution.The two patterns of stratiform precipitation distribution in Henan Province are N(D)=7373.9exp(-3.67D)and N(D)=10492.05D1.62exp(-5.11D),respectively.