Analysis of Dual-Polarimetric Radar Variables and Quantitative Precipitation Estimators for Landfall Typhoons and Squall Lines Based on Disdrometer Data in Southern China

Abstract

Typhoon rainstorms often cause disasters in southern China. Quantitative precipitation estimation (QPE) with the use of polarimetric radar can improve the accuracy of precipitation estimation and enhance typhoon defense ability. On the basis of the observed drop size distribution (DSD) of raindrops, a comparison is conducted among the DSD parameters and the polarimetric radar observation retrieved from DSD in five typhoon and three squall line events that occurred in southern China from 2016 to 2017. A new piecewise fitting method (PFM) is used to develop the QPE estimators for landfall typhoons and squall lines. The performance of QPE is evaluated by two fitting methods for two precipitation types using DSD data collected. Findings indicate that the number concentration of raindrops in typhoon precipitation is large and the average diameter is small, while the raindrops in squall line rain have opposite characteristics. The differential reflectivity (ZDR) and specific differential phase (KDP) in these two precipitation types increase slowly with the reflectivity factor (ZH), whereas the two precipitation types have different ZDR and KDP in the same ZH. Thus, it is critical to fit the rainfall estimator for different precipitation types. Enhanced estimation can be obtained using the estimators for specific precipitation types, whether the estimators are derived from the conventional fitting method (CFM) or PFM, and the estimators fitted using the PFM can produce better results. The estimators for the developed polarimetric radar can be used in operational QPE and quantitative precipitation foresting, and they can improve disaster defense against typhoons and heavy rains.

Microphysical features of typhoon and non-typhoon rainfall observed in Taiwan, an island in the northwestern Pacific

“…From the 2-dimensional video disdrometer (2DVD) measurements in eastern China, Chen et al (2017) determined the polarimetric radar variables for typhoons, mei-yu, and squall line precipitations, and they revealed discrete alterations among these weather systems. Over southern China, distinct differences in the rain integral parameters of typhoons and squall lines were perceived by Zhang et al (2019), and they concluded that it is essential to adopt precipitation-specific rainfall estimators. An examination of typhoons and mei-yu season RSDs in Japan affirmed maritime behavior in typhoons and continental behavior in mei-yu rainfall (Chen et al, 2019).…”

Raindrop Size Distribution Characteristics for Tropical Cyclones and Meiyu-Baiu Fronts Impacting Tokyo, Japan

“…Previous studies revealed that the tropical cyclone RSDs varied significantly across different climate regions [4][5][6][7][8][9][10]. Most studies focused on typhoons making landfall on the East Asia continent, such as southeast China [7,9,10], which is strongly influenced by a continental climate, and Wen et al [9] found that typhoon raindrops in continental China are smaller and have higher concentrations than those in the Pacific and Atlantic. However, few studies have been conducted on the impacts of typhoons in the midlatitude area around the Japan Islands, which is greatly influenced by the ocean climate.…”

Microphysical features of typhoon and non-typhoon rainfall observed in Taiwan, an island in the northwest Pacific

“…The polarimetric radar variables computed with the 2DVD for the typhoon, Mei-yu, and squall line precipitations over Easter China showed distinct differences among these precipitation types (Chen et al, 2017). Over south China, distinct differences in rain integral parameters of typhoons and squall lines were noticed by Zhang et al (2019). They concluded that it is crucial to adopt the precipitation specific rainfall estimators.…”