佛山市2014年秋季连阴雨天气环流和水汽特征分析

Analysis of the Characteristics of Circulation and Water Vapor for a Sustained Autumn Rainy Weather of Foshan in 2014

利用NCEP/NCAR 1°×1°再分析资料和国家站观测数据,对佛山市2014年秋季的一次连阴雨天气进行时空分布、环流背景和水汽条件分析。结果表明:该次过程的累计降雨量比常年同期偏多200%～700%,北部的降雨大于南部地区,温度的变化总体上为先明显下降再缓慢回升;11月1—12日中层波动频繁以及近地面层弱冷空气活跃是该次连续阴雨天气的主要成因,较明显冷空气影响、中层西北风大风速带建立标志着阴雨天气结束。连阴雨期间在降雨强度大、降雨时间集中时段均有深厚的湿层和明显的水汽辐合;而在降雨停歇时段,700 hPa位势高度相对湿度小于90%,且925 hPa为一致的水汽辐散。

Using the NCEP/NCAR 1°×1° reanalysis and observations from a national observation station, this paper analyzed the spatiotemporal distribution, circulation background and water vapor conditions of a sustained autumn rainy weather of Foshan in 2014. The result is shown as follows. The accumulated rain amount for this process was 200% to 700% more than that of the same period of the average year, with the amount larger in the north than in the south and a general temperature variation that first dropped significantly and then rose slowly. The sustained rainy weather was mainly caused by frequent mid-level waves and active weak cold air in the near-surface layer from November 1 to 12. When the cold air got stronger and a zone established of strong mid-level northwesterlies, the weather came to an end. During the period in which the rain rate was large and rain time was concentrated, the sustained rain was accompanied with a deep wet layer and significant convergence of water vapor. On the other hand, when the rain had a break, relative humidity was less than 90% at the geopotential height of 700 hPa and there was consistent water vapor divergence at 925 hPa.