河南省2002年秋季一次层状云降水过程的观测研究

在涡旋云系和低槽切变云系的先后影响下，2002年10月16-20日河南省产生了主要由层状云形成的小到中雨天气。中低层对流不稳定层结和偏东偏南暖湿气流为降水提供了有利条件。较厚的云体多为混合相结构，雷达回波普遍有明显亮带，过冷云区冰相粒子含量较过冷水高，暖云区云水含量偏低，雨水浓度基本随雨滴直径指数递减，较大雨滴对雨强的贡献大。推测总体降水机制可能为，冷云过程强于暖云过程，冰粒子凝华增长是其主要增长方式，冰粒子融化对地面降水有较大贡献。云系宏微观结构和降水特征都表明在层状云系不同部位存在不均匀性。

Observational Analysis of Stratiform Cloud Precipitation in Autumn 2002 in Henan Province

Stratiform cloud precipitation processes in Henan Province on October 16--20,2002, were mainly caused by trough-line, low-level shear and surface trough. The vortex and trough cloud systems produced light to moderate rains. The convectively unstable stratification and the easterly and southerly warm/moist flows in middle- and low-levels provided advantageous conditions for the rainfall. Deep clouds had a mixed-phase structure, and the radar echoes had distinct bright bands in most cases. The water content of ice particles was higher than that of supercooled droplets in supercooled cloud layers, and the water content of cloud droplets was relatively low in warm cloud layers. Raindrop number concentrations reduced exponentially with raindrop diameters, and large raindrops contributed more to the rainfall rate. It can be inferred that the cold-cloud process was stronger than the warm-cloud process, and the deposition of ice particles was its major growth mode, and the melting of ice-phase particles had the greatest contribution to the surface rainfall. Both the macro- and micro-physical structures of cloud systems and precipitation features indicate that heterogeneity existed in different parts of the stratiform cloud systems.