Extreme Precipitation Produced by Relatively Weak Convective Systems in the Tropics and Subtropics

Abstract

This study investigates warm‐season extreme precipitation events (EPEs) with the focus on the less‐attended weak convection (WeEPEs) using spaceborne radar observations. WeEPEs are compared to EPEs with intense convection (InEPEs), including their frequency/location, convective structures, and storm environments. WeEPEs and InEPEs both account for about 30% of the EPEs, highlighting the importance of WeEPEs. Overland WeEPEs mainly occur over key monsoon regions and maximize over windward sides of coastal mountains likely due to orographic enhancement. WeEPEs develop under conditions with deep moist profiles and strengthened low‐level onshore flows. Radar, microwave, and lightning proxies all suggest a weak updraft and limited ice contents in WeEPEs. However, vertical radar profiles of WeEPEs exceptionally increase (∼15 dBZ) downward below the melting level, indicating substantial raindrop growth and/or concentration increase through very active warm‐rain processes. This study provides useful guidelines for evaluating high‐resolution model simulations and satellite rainfall retrievals on extreme precipitation.

Event‐based precipitation characteristics related to cloud‐top temperature during pre‐summer rainy season over south China

“…RCs with mode of TB 10.4 at 230-265 K. Despite the low cloud top, these RCs contributed around 39.8% of the total rainfall amount. This result supported that many extreme precipitation events are produced by relatively weak convective systems (Xu et al, 2022). RCs with mode of TB 10.4 at 230-265 K were related to the quasi-stationary front over south China; therefore, they were distributed near the average location of front at 23 -27 N. The mid-level pressure gradient over the study region and westerly winds were significantly stronger than the other two classes.…”

“…However, the average dBN w of convective precipitation for RCs with mode of TB 10.4 < 230 K (~32.2) was significantly lower than extreme precipitations (~39.8), showing that there was more prominent coalescence warm‐rain process for the triggering of extreme events. RCs with mode of TB 10.4 at 230–265 K. Despite the low cloud top, these RCs contributed around 39.8% of the total rainfall amount. This result supported that many extreme precipitation events are produced by relatively weak convective systems (Xu et al ., 2022). RCs with mode of TB 10.4 at 230–265 K were related to the quasi‐stationary front over south China; therefore, they were distributed near the average location of front at 23°–27°N.…”

Evaluating the Variability of Simulated Raindrop Size Distributions in the “21·7” Henan Extremely Heavy Rainfall Event

“…Xu et al. (2022) have also found that convection with limited ice contents can equally bring heavy rainfall. Moreover, Dolan et al.…”

“…First, Hamada et al (2015) have obtained the weak linkage between the heaviest rainfall and tallest convective storms. Xu et al (2022) have also found that convection with limited ice contents can equally bring heavy rainfall. Moreover, Dolan et al (2018) have identified two distinct DSD types both causing heavy rainfall from global observations, which are characterized by relatively larger (smaller) raindrop mean size and lower (higher) number concentration, and correspond to the warm-rain (ice-based) convection.…”

How Do the Convective and Microphysical Characteristics of Extreme Precipitation Over the Pearl River Delta at Monsoon Coast Vary With Increasing Rainfall Extremity?

“…Xu et al. (2022) reported an equal contribution (30%) from intense and weak convection over tropical and subtropical land based on the space‐borne PR observations. Huang et al.…”