不同高度冷空气侵入登陆台风暴雨过程对比分析

为了解不同高度冷空气与登陆台风结合,暴雨事件的机理和降水特征差异。以1323号“菲特”和1601号“尼伯特”登陆台风,分别引起江苏东南部2013年10月7—8日和2016年7月11日异常暴雨事件为例,进行对比分析。结果表明：“10·7—8”暴雨期间,低层冷空气侵入“菲特”残留低压,与“丹娜丝”北侧东风急流结合,大气层结由对流不稳定转为条件性对称不稳定,低层斜压锋生、辐合加强,高层强辐散,倾斜对流发展,造成分布均匀持续时间长的层、积混合型强降水,暴雨中心与低层MPV2异常区和锋生区对应;“7·11”暴雨则是“尼伯特”残留低压倒槽顶部附近低层诱生出中尺度低压并发展,冷空气从中层侵入,强对流不稳定层结建立,对流有效位能释放形成强烈的垂直上升运动,造成分布不均、持续时间短、短时雨强大的对流性强降水,暴雨中心位于地面中尺度辐合线及温度脊附近。“10·7—8”暴雨过程,台风北侧的东风急流提供了充足的水汽;“7·11”暴雨过程的水汽,则主要来源于本地和中尺度低压右侧的偏东风输送。不同高度冷空气侵入登陆台风系统,造成大气层结稳定度和上升运动的形成机制不同,其降水特征存在显著差异,在预报业务中值得关注。

Comparative Analysis of Rainstorm Processes of Landing Typhoon Invaded by Cold Air at Different Heights

This study aims to understand the mechanism of rainstorm events and the difference of precipitation characteristics of cold air at different heights combining with landing typhoons. The unusual rainstorm events on October 7 - 8, 2013 and July 11, 2016 in southeast Jiangsu caused by the landing typhoon No. 1323 “Fitow” and No. 1601 “Nepartak” respectively were used for comparative analysis. The results showed that during the “10·7 - 8” rainstorm, the low-level cold air intruded into the “Fitow” residual low pressure, combined with the easterly jet on the north side of “Danas”, the atmospheric stratification changed from convective instability to conditional symmetric instability. The frontogenesis and convergence of the low-level baroclinic increased, the high-level strong divergence and the inclined convection developed, those led to the stratigraphic and cumulative mixed heavy precipitation with uniform distribution and long duration, the center of the rainstorm had the same location with the frontogenesis and MPV2 in the lower troposphere. The “7.11” rainstorm was caused by the development of mesoscale low pressure induced by the lower layer near the top of the residual low pressure inverted trough of “Nepartak”. The cold air intruded into the middle level, the strong convective instability stratification was established, and the release of the convective effective potential energy formed a strong vertical upward movement, those resulted in strong convective heavy precipitation with uneven distribution, short duration and strong short-term rainfall, the rainstorm center was located near the surface mesoscale convergence line and temperature ridge. During the “10·7 - 8” rainstorm, the easterly jet on the north side of the typhoon provided sufficient water vapor. Water vapor in the process of “7.11” rainstorm mainly came from the easterly transport of the right side of the local and mesoscale low pressure. Different heights of cold air intruding into the landing typhoon system could result in different formation mechanisms of atmospheric stratification stability and ascending motion causing significant differences in precipitation characteristics, and deserves attention in the operational forecast.