An Automatic Recognition Method for Airflow Field Structures of Convective Systems Based on Single Doppler Radar Data

Ping Wang,Kai Gu,Bingjie Dou,Jinyi Hou

doi:10.3390/atmos11020142

Abstract

Airflow structures within convective systems are important predictors of damaging convective disasters. To automatically recognize different kinds of airflow structures (the convergence, divergence, cyclonic rotation, and anticyclonic rotation) within convective systems, an airflow structure recognition method is proposed, in this paper, based on a regular hexagonal template. On the basis of single Doppler radar data, the template is designed according to the appearance model of airflows in radial velocity maps. The proposed method is able to output types and intensities of airflow structures within convective systems. In addition, the outputs of the proposed method are integrated into a projection map of the airflow field structure types and intensities (PMAFSTI), which is developed in this work to visualize three-dimensional airflow structures within convective cells. The proposed airflow structure automatic recognition method and the PMAFSTI were tested using three typical cases. Results of the tests suggest the following: (1) At different evolution stages of the convective systems, e.g., growth, split, and dissipation, the three-dimensional distribution of the airflow fields within convective systems could be clearly observed through the PMAFSTI and (2) on the basis of recognizing the structures of the airflow field, the complex airflow field, such as a squall line, could be further divided into several small parts making the analysis of convective systems more scientific and elaborate.

Highlights

IntroductionUpdrafts and downdrafts in convective systems can form complex and variable airflow fields
Updrafts and downdrafts in convective systems can form complex and variable airflow fields.The convergence, divergence, cyclonic rotation, and anticyclonic rotation are the four structure types of the airflow field
An anticyclonic rotation is defined as a circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere

Summary

Introduction

Updrafts and downdrafts in convective systems can form complex and variable airflow fields. The convergence, divergence, cyclonic rotation, and anticyclonic rotation are the four structure types of the airflow field. If two prevailing flows in the atmosphere meet and interact, it is defined as a convergence [1]. The inverse of a convergence is a divergence. A cyclonic rotation [2] is defined as a circulation of winds around a central region of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. An anticyclonic rotation is defined as a circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere

Objectives

Findings

Discussion

Conclusion