冷空气强度对云南初夏强降水天气的影响
A Study of Cold-air Force to Heavy Rainfall during Early Summer in Yunnan
中文摘要：
对云南初夏两次不同冷空气强度下的强降水天气过程的大尺度环流背景、中尺度系统和水汽输送特征及来源情况进行了较为详尽的对比分析研究。结果表明：（1）这两次强降水过程都是印缅槽与东亚冷槽相互作用的结果，但冷暖空气的强度有着明显差异，较强的冷空气更利于冷暖空气交汇于云南地区。（2）近地层中尺度辐合线的发展与冷空气强度有关，较弱的冷空气使近地层中尺度辐合线有沿地势走向的特征；而较强的冷空气则使低层中尺度辐合线的发展演变只与冷暖空气的势力对比相关，与云南的地形特征相关不大。强降水落区与低层辐合线有着很好的一致性。（3）锋区强度分析揭示了这两次强降水过程的冷空气运动状况，势力较弱的冷空气产生的锋区位置较低，基本沿地势渗透进入云南，局地性降水较强；而较强冷空气产生锋区的位置较高，降水区域多为沿锋区的连续雨带。同时，这两次强降水过程都与高低空急流有较好的相关性。（4）对这两次云南水汽输送分析表明，直接影响云南强降水的水汽输送主要来源于孟加拉湾，并且在较强的冷暖空气交汇下，水汽辐合可存在于较高的气压层，从而产生较强降水。
中文关键词：
冷空气，暴雨，中尺度，水汽输送
KeyWords：
cold air, heavy rainfall, mesoscale system, moisture transportation
Abstract：
In this paper, the contrast study of different cold-air forces has been done in large-scale circulation, meso-scale systems and vapor budget for two heavy rainfalls in Yunnan during early summer. The results show that the two courses which had similar large-scale circulation, were the result of interaction between Indian-Myanmar trough and East Asia cold (thermodynamic) trough, but the force of cold and warm air was different from each other. The stronger the cold air was, the more convenient for the meet of cold and warm air in Yunnan. The development of the mesoscale convergence lines in the lower part related to the force of the cold air. The topography of Yunnan had influence to mesoscale convergence lines when cold air wasn’t strong enough. The precipitation position only related with mesoscale convergence lines. The analysis for the frontogenesis of the two processes shows, the location of frontogenesis could reach upper troposphere when the cold air was strong enough. Otherwise, the cold air entered into Yunnan only along the topography. Furthermore, the cause of the two heavy rainfalls related with the interaction between lower and upper jet. The analysis for water vapor supply shows that main water vapor source of heavy rainfall may come from Bay of Bengal. Meanwhile, water vapor could be brought to middle troposphere under strong intercourse between cold and warm air, and then caused heavy rainfall.