Springtime mesoscale convective systems over South China: a historic radar image-based analysis of climatological features, interannual variability, and potential connections with surface aerosol

We objectively analyzed historic radar reflectivity images and diagnosed mature mesoscale convective systems (MCSs) in South China during the spring season (March to May) of 2009-2019. Our goal was to understand the climatological features of mature MCSs, their interannual variations, and potential connections with surface aerosol pollution. Springtime MCSs over South China were most frequently observed in the central and east-coastal parts of Guangdong Province. The mean monthly half-hourly counts of MCSs over South China in March, April, and May were 103 +/- 83, 274 +/- 298, and 337 +/- 225, respectively, with considerable variability from year to year. Approximately 89% of springtime MCSs over South China had a linear or quasi-linear structure, with convective precipitation covering on average 34% of the total precipitating area of each individual MCS, anmied 63% of MCSs consisted of a stratiform precipitation area trailing the convective precipitation. In March, MCSs occurred most frequently mid-day; in April and May, MCSs were most frequent around midnight. From 2013 to 2019, the MCS occurrences in April were significantly lower during years with more aerosol pollution days. This finding potentially supported our previous model study's finding that elevated anthropogenic aerosol levels may suppress April MCS occurrences in South China via aerosol-cloud-radiation interactions. Further research is required to better understand the intricate relationship between aerosol abundance and MCS activities in this region. Mesoscale convective systems (MCSs) are the main cause of heavy precipitation and weather disasters over South China in spring. We objectively analyzed historic radar images and diagnosed the climatological features of springtime mature MCSs over South China. Springtime MCSs over South China occurred most frequently over central and east-coastal Guangdong and typically exhibited a linear or quasi-linear shape. The occurrences of MCSs varied considerably from year to year. We found that the MCS occurrences in April were lower during years with more aerosol pollution days This finding potentially supported our previous model study that high levels of anthropogenic aerosols suppress MCS occurrences in South China in April.