黄山雨滴下落过程滴谱变化特征

利用2011—2012年4—10月安徽省黄山山顶和山底两个站点同时采集的雨滴谱数据，共选取17个降水个例，将17个降水个例分为对流云降水和层云降水，对不同高度和不同云系降水雨滴谱特征分析得出以下结论:对于不同云系的降水，山顶平均雨滴数浓度大于山底，平均峰值直径和平均质量半数直径在下落过程中均增加，平均雨强和平均雷达反射率因子变化幅度较小。不同云系的雨滴在下落过程中，雨滴谱谱宽变化较小，但雨滴谱均从M-P (Marshall-Palmer) 分布转向了Gamma分布。降水粒子在下落过程中，大部分通道的数浓度均出现损失，最大损失超过50%，随着粒子尺度增加损失逐渐减少，大粒子数浓度在降落时有所增加，增加幅度为10%左右，降水粒子的碰并和蒸发过程很可能是造成降水粒子下落过程中滴谱变化的两个主要原因。

Characteristics of Raindrop Falling Process at the Mount Huang

Utilizing raindrop spectrum data recorded by PARSIVEL of April-Octomber from 2011 to 2012 at the top and foot of the Mount Huang, 17 precipitation cases are collected, which divided into convective cloud precipitation and stratiform cloud precipitation. Characteristics of raindrop spectrum in different height and cloud from 17 precipitation cases are analyzed.Observed results show that the average concentration of raindrops at the top of the mountain is higher than that at the foot of the mountain in both convective cloud and stratiform cloud precipitation, the average peak diameter and the average mass median diameter both increase during falling process, but average intensity and radar reflectivity both have a smaller change. Neither convective cloud nor stratiform cloud raindrop spectrum distribution broadens from top to foot of the Mount Huang, but the spectrum shapes of raindrop change from M-P (Marshall-Palmer) to Gamma. Raindrop loses at most bins when falling from top to foot of the mountain, the maximum loss appears at the third bin of raindrop spectrum, with the loss percentage exceeding 50%. The concentration of bigger raindrop of stratiform cloud begins at the 11th bin (with feature diameter of 1.375 mm) and convective cloud raindrop begin at the 13th bin (with feature diameter of 1.875 mm) increase during falling process. The increase amplitude is lower than 10% except the 12th bin (with features diameter of 1.625 mm) and the 13th bin of stratiform cloud raindrop, and the increase at these two bins are 10.8% and 11.9%, respectively. Evaporation accompanies with the whole falling process, which has bigger effects on small raindrops than big ones, leading to lower concentration of smaller raindrop at the foot of the mountain. These losses gradually reduce along with raindrop diameter increasing due to effects of coagulation process of raindrop become stronger along with raindrop diameter increasing. Therefore, these changes occurring during falling process may be caused by both evaporation and coagulation process of raindrop.