华中区域极端降水天气形势及物理量异常度特征

选取1960—2012年间共139例极端降水个例,对其降水特征、天气形势及物理量异常度进行了分类对比研究。结果发现:华中区域极端降水主要发生在四种不同的天气形势下,即纬向型、经向型、台风西风带冷槽结合型和短波槽前低涡暖切型,其个例占比分别为42.4%,30.2%,17.3%,10.1%;台风西风带冷槽结合型在暴雨站数、极端降水站数、极端降水量平均值均居四类最大,纬向型和经向型次之,短波槽前低涡暖切型最小;低层水汽辐合、中低层上升速度、低层风场辐合及气旋性涡度,高层风场辐散和大气可降水量的异常比例超过50%,是极端降水物理量异常的共性特征。个性特征为:纬向型500 hPa比湿异常比例较高,经向型中低层暖平流异常比例较高,台风西风带冷槽结合型500 hPa正涡度平流和中低层比湿异常比例较高,短波槽前低涡暖切型与其他类比异常量更集中于边界层且大气可降水量异常比例低。此外,极端降水预报除了要关注物理量异常程度,降水的持续时间也是重要因素之一。

Characteristics of Extreme Precipitation Weather Situation and Physical Quantity Anomaly in Central China

This paper selects 139 extreme precipitation cases from 1960 to 2012 to study the characteristics of precipitation, weather situation and physical quantity anomaly. The findings indicate that, the extreme precipitation in central China mainly occurs in four different weather situations, namely, the zonal type, the meridional type, the typhoon and cold trough combined type and the short wave trough with warm shear type. The proportions of cases are 42.4%, 30.2%, 17.3% and 10.1%, respectively. The typhoon and cold trough combined type stands on the top in the four types of heavy rain stations, extreme precipitation stations and the extreme rainfall, followed by the zonal type and the meridional type, while the short wave trough with warm shear type is the lowest. The anomaly ratios of low-level water vapor convergence, mid-low-level rising velocity, low-level wind convergence and cyclonic vorticity, high-level wind divergence and atmospheric precipitable water exceeding 50% are the common features of extreme precipitation anomalies. The individual characteristics are that the anomaly ratio of 500 hPa specific humidity in the zonal type is higher, the anomaly ratio of warm advection in the meridional type is higher, the anomaly ratio of 500 hPa positive vorticity advection and specific humidity in the typhoon and cold trough combined type is higher. Moreover, in the short wave trough with warm shear type, the abnormal physical quantity is more concentrated in the boundary layer, and the abnormal proportion of atmospheric precipitable water is low. In addition, besides paying attention to the degree of abnormal physical quantities, the duration of precipitation is also one of the important factors in extreme precipitation prediction.