Mesoscale and Microphysical Characteristics of a Double Rain Belt Event in SouthChina on May 10–13, 2022

A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation. We examined the differences in the mesoscale characteristics and microphysics of thefrontal and warm sector rain belts that occurred in South China on May 10–13, 2022. The southern rain belt occurred in anenvironment with favorable mesoscale conditions but weak large-scale forcing. In contrast, the northern rain belt wasrelated to low-level horizontal shear and the surface-level front. The interaction between the enhanced southeasterly windsand the rainfall-induced cold pool promoted the persistent growth of convection along the southern rain belt. The con vective cell propagated east over the coastal area, where there was a large temperature gradient. The bow-shaped echo inthis region may be closely related to the rear-inflow jet. By contrast, the initial convection of the northern rain belt wastriggered along the front and the region of low-level horizontal shear, with mesoscale interactions between the enhancedwarm-moist southeasterly airflow and the cold dome associated with the earlier rain. The terrain blocked the movement ofthe cold pool, resulting in the stagnation of the frontal convective cell at an early stage. Subsequently, a meso-γ-scalevortex formed during the rapid movement of the convective cell, corresponding to an enhancement of precipitation. Therepresentative raindrop spectra for the southern rain belt were characterized by a greater number and higher density ofraindrops than the northern rain belt, even though both resulted in comparable hourly rainfalls. These results help us betterunderstand the characteristics of double rain belts over South China.

Mesoscale and Microphysical Characteristics of a Double Rain Belt Event in SouthChina on May 10–13, 2022

A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation. We examined the differences in the mesoscale characteristics and microphysics of thefrontal and warm sector rain belts that occurred in South China on May 10–13, 2022. The southern rain belt occurred in anenvironment with favorable mesoscale conditions but weak large-scale forcing. In contrast, the northern rain belt wasrelated to low-level horizontal shear and the surface-level front. The interaction between the enhanced southeasterly windsand the rainfall-induced cold pool promoted the persistent growth of convection along the southern rain belt. The con vective cell propagated east over the coastal area, where there was a large temperature gradient. The bow-shaped echo inthis region may be closely related to the rear-inflow jet. By contrast, the initial convection of the northern rain belt wastriggered along the front and the region of low-level horizontal shear, with mesoscale interactions between the enhancedwarm-moist southeasterly airflow and the cold dome associated with the earlier rain. The terrain blocked the movement ofthe cold pool, resulting in the stagnation of the frontal convective cell at an early stage. Subsequently, a meso-γ-scalevortex formed during the rapid movement of the convective cell, corresponding to an enhancement of precipitation. Therepresentative raindrop spectra for the southern rain belt were characterized by a greater number and higher density ofraindrops than the northern rain belt, even though both resulted in comparable hourly rainfalls. These results help us betterunderstand the characteristics of double rain belts over South China.