2010年冬末春初“回南天”环流背景场特征分析——以惠州市为例

Analysis of the Circulation Characteristics of the "Continuous Wet Weather" during February-March in 2010:A Case Study of Huizhou City,Guangdong

利用NCEP/NCAR再分析资料和MICAPS实况数据,对广东惠州市2010年冬末春初的2次较严重的、持续时间较长的"回南天"天气过程进行总结分析。结果显示:发生"回南天"的前期一般出现较长时间的低温阴雨天气,使得地面及墙面等物体表面温度较低,空气湿度较大;"回南天"期间,500hPa北支系统偏北,冷空气难以南下,南支波动活跃,华南地区主要处于南支槽前,其前强盛的西南暖湿气流为"回南天"带来了充足的水汽条件,底层地面冷高压北收,西南低槽不断更替发展,华南地区主要处于地面低压槽前侧,且地面风速较小,对流层低层有较强的逆温层存在。

Continuous wet weather often occurs at the turn between winter and spring in southeastern China,which makes great impacts on social and economic activities.For understanding the causes and thereby improving the prediction of the continuous wet weather,in this paper,by using the NCEP/NCAR reanalysis data and MICAPS data,the continuous wet weather occurred in Huizhou during Feb-Mar 2010 was analyzed.The result shows that sustained cold and wet conditions may induce lower temperature at the surface of object before continuous wet weather.During the period of continuous wet weather,as the westerly trough was located at the north of middle latitudes in the Northern Hemisphere,no obvious cold air was found in southeastern China.Southern branch of westerlies and strong southwesterly prevailed over South China,which transported substantial moisture to this region.In addition,weak surface wind and prolonged surface low trough were observed over southeastern China.Those factors would be important for the generation and maintenance of continuous wet weather.