Three-Dimensional Structure Analysis and Droplet Spectrum Characteristics of Southwest Vortex Precipitation System Based on GPM-DPR

Abstract

This study is the first in the region to use Global Precipitation Mission Dual-Frequency Precipitation Radar (GPM-DPR) and Fengyun-2G (FY-2G) observations to qualitatively and quantitatively study the Southwest Vortex evolution characteristics during the flood season from 2019 to 2021. Furthermore, vertical characteristics of the two main precipitation types in the Southwest Vortex, stratiform and convective, were statistically analyzed at different life stages, including horizontal and vertical distribution of precipitation particles, droplet spectrum characteristics, and vertically layered precipitation contribution. The results showed that: (1) The typical convective precipitation (CP) in the developing and mature stages has strong reflectivity distribution centers in the upper and lower layers, showing characteristics related to terrain. Additionally, the high-level hydrometeor particles are mainly solid precipitation particles, and particles in the lower layers collide and coalesce in the violent vertical motion of the airflow. (2) For the three stages of CP, the reflectivity below melting layer (ML) first showed a rapid weakening trend toward the surface and then remained unchanged, significantly changing its vertical structure. The main rainfall type of the Southwest Vortex system was stratiform precipitation (SP) in the three stages. (3) In the two types of cloud precipitation, the developing stage is generally composed of large and sparse precipitation particles, the mature stage of large and dense precipitation particles, and the dissipating stage of small and sparse precipitation particles. The findings of this study reveal the three-dimensional refined structure and vertical variation characteristics of different life stages of the Southwest Vortex precipitation cloud system and provide important tools and references for improving the accuracy of numerical models and the forecast level of short-term heavy precipitation under complex terrain.

Case Study on the Evolution and Precipitation Characteristics of Southwest Vortex in China: Insights from FY-4A and GPM Observations

“…Near-surface precipitation mainly consists of liquid precipitation, with the melt layer occurring at approximately 5.5 km (Figure 11). This finding aligns with Wang et al's (2022) conclusion regarding the height of the melt layer in SWV stratus clouds [21]. Generally, due to the changes in volume and surface features of droplets during melting, droplet reflectivity is strongest at some time within the melting process, corresponding to the single bright band in the reflectivity profile [47].…”

“…The peak height of the Ku-band echo is roughly 10 km, with the most intense echo at about 34 dBZ. In conjunction with Figure 9c, the area with weak echoes is expansive, implying subdued convective particle activity during the dissipating stage [21].…”

“…The peak height of the Ku-band echo is roughly 10 km, with the most intense echo at about 34 dBZ. In conjunction with Figure 9c, the area with weak echoes is expansive, implying subdued convective particle activity during the dissipating stage [21]. The dominant precipitation elements in each life stage are characterized by solidphase precipitation above 5.5 km in the vertical direction.…”

“…In contrast, the lower and middle layers comprise larger and denser water particles. These particles continually collide and grow during falling, leading to heavy precipitation [21]. In the dissipating stage, smaller and sparser water particles dominate, which are not conducive to generating heavy precipitation.…”

“…Numerous scholars have leveraged GPM data to study SWV precipitation, yielding significant results. For example, Wang et al (2022) utilized GPM-DPR observation data to qualitatively and quantitatively investigate the evolution characteristics of SWV during the flood season from 2019 to 2021, providing insights into the horizontal and vertical distribution characteristics and spectral properties of precipitation particles [21]. Mao et al (2022) analyzed SWV events that influenced precipitation in central and eastern China during the warm season from 2010 to 2020 using data from GPM-DPR and FY-2F.…”