我国南方致洪锋面暴雨中的两类锋生机制研究

The frontal rainstorms frequently occur in the south of China in summer. It is an important high impact weather easily leading to flood. Focusing on the frontogenesis mechanism which is critical to the diagnosis and prediction of frontal rainstorm, this research project mainly studies the frontogenesis processes and the vertical motion (frontal circulation) forced by frontogenesis. (1) During the frontal rainstorm in the south China, the atmosphere near the frontal zone has large humidity, but is not saturated everywhere. Therefore, a thermodynamic frontogenesis function based on generalized potential temperature is constructed, describing the frontogenesis process in nonuniformly saturated moist atmosphere. Then how this kind of frontogenesis forces vertical motion (directly triggering frontal rainstorm) is further explored. (2) A dynamic deformation-based frontogenesis method, which can directly drive the temperature and humidity contrast, simply and intuitively describe diverse frontogenesis, is developed. (3) The two kinds of frontogenesis methods are evaluated to establish a set of simple and practical platform to be applied to diagnosis and predict the frontal rainstorm. This study will enhance the cognition and improve the prediction of frontal rainstorm in the south of China. It not only provides the scientific basis for the prediction and warning of frontal rainstorm hazard in the south of China, but also is a significant demand of national disaster prevention and mitigation.

我国南方夏季致洪锋面暴雨频发，是一种重要的高影响天气。本项目从锋生过程和锋生强迫的垂直运动（锋面环流）着眼，研究对锋面暴雨诊断和预测至关重要的锋生机制。（1）针对我国南方暴雨锋生区湿度大但并非处处饱和的特点，发展基于广义位温的热力学锋生诊断方程，探究暴雨锋生区非均匀饱和真实湿大气的锋生过程，揭示其激发垂直运动（直接启动致洪锋面暴雨）的锋生机制；（2）针对南方锋面暴雨锋生类型多样的特点，构建基于变形场驱动的动力学锋生函数，简单直观描述多样性锋生过程，揭示由于流场的改变直接驱动温湿等值线密集以及垂直环流的锋生机制；（3）评估两类锋生在锋面暴雨分析和预测中的适用性，最终基于上述锋生机制分析，建立一套具有可操作性和实用的南方锋面暴雨诊断和预测方法，以提升对南方锋面暴雨形成机制的认知与预测预报水平。这不但可为我国南方锋面暴雨灾害预测预警提供科学依据，亦是国家防灾减灾的重大需求。

本项目选取我国南方锋面暴雨的多次典型天气过程，从锋生过程和锋生强迫的垂直运动（锋面环流）着眼，研究了对锋面暴雨诊断和预测至关重要的锋生机制。采用动力过程理论推导，结合观测资料分析、高分辨数值模拟、动力-统计相结合的诊断方法，并借助拉格朗日分析技术等，（1）构建出一类基于广义位温的热力学锋生函数，可较好地描述我国南方锋面暴雨区湿大气的锋生过程，这无论对锋生机制理论研究还是对锋面暴雨的预测理论发展都有贡献；（2）推导出另一类基于变形场驱动的动力学锋生诊断方程，这在变形场主导的流型中具有一定普适性，为多样性锋生及相关的锋面暴雨分析提供了新思路；（3）建立了两类锋生与垂直运动的联系，并给出两类锋生机制在南方锋面暴雨诊断和预示中的适用范围及优先性排序。以上这些研究为我国南方锋面暴雨的分析提供了理论基础，并为搭建实用易操作的预测预报平台提供了科学依据。