对流层顶折叠检测新方法及其在中纬度灾害性天气预报中的应用

对流层顶折叠是中纬度地区对流层上层—平流层下层区域(简称UT/LS)内的一个重要的大气现象,它与气旋生、暴雨强对流触发以及降水增幅密切相关。由于这些天气条件下的大气状况异常复杂,因此目前国际上普遍采用的基于干大气条件的对流层顶折叠检测方法存在很大局限性。本文在借鉴已有的卫星资料和数值预报相结合的模式识别法的基础上,通过统计分析的方法建立了高层大气水汽与广义湿位涡、臭氧浓度的关系以及对流层顶折叠与高空急流的位置关系,同时考虑了动力对流层顶高度在判识过程中的辅助作用,建立了一套基于FY-2E静止气象卫星遥感数据的,适用于与暴雨强对流有关的对流层顶折叠动态监测新方法。在利用FY-3A和FY-3B反演的臭氧总量、臭氧垂直廓线以及ECMWF Interim资料计算的位涡等资料对算法进行精度验证的基础上,将该方法在2012年7月21日北京特大暴雨天气过程以及2013年5月14~17日华南大暴雨天气过程的监测和分析上进行了应用,并取得了较好的效果。从应用效果看,本文提出的这种对流层顶折叠识别方法是合理可行的,并具有一定的应用价值,可为中纬度地区暴雨强对流天气的监测和预警提供参考指标。

A New Method for Tropopause Folding Detection and Its Application in Middle-Latitude Disastrous Weather Forecasting

Tropopause folding is an important mid-latitude atmosphere phenomenon occurring within the upper troposphere and lower stratosphere that always correspond to cyclogenesis, rainstorm and convection generation, and precipitation enhancement. Because the atmospheric environment for these above-mentioned weather phenomena is very complicated, preexisting popular schemes that do not consider water vapor may not be suitable for detecting the accompanying tropopause folding. Regarding the merits and demerits of the pattern recognition scheme on the basis of satellite and numerical data, a dynamic new scheme based on FY-2E geostationary weather satellite data is presented to detect tropopause folding related to rainstorms. The core concept of this scheme is based on the statistical relationship between tropopause folding and the water vapor at the high-level troposphere, general moist potential vorticity, ozone, and upper-level jet while simultaneously considering the auxiliary effect of the height of the dynamic tropopause. After accuracy verification using the total amount of ozone and ozone profile operational products retrieved by FY-3A and FY-3B and the potential vorticity calculated by the European Center for Medium-range Weather Forecasting (ECMWF) Interim data, this scheme is applied to analyze two typical middle-latitude weather processes. One is the famous Beijing extreme rainfall of July 21, 2012, and the other is the South China rainstorm that occurred during May 14-17, 2013. A good application effect of both cases suggests that our new method for tropopause folding detection is feasible and can be helpful in middle-latitude disastrous weather monitoring and forecasting.