Impacts of El Niño‐Southern Oscillation on Mesoscale Convective Systems in China

Abstract

During spring and summer, mesoscale convective systems (MCSs) account for approximately 50% of total precipitation and 75.6% of extreme precipitation across South and East China. Although it is well known that El Niño‐Southern Oscillation (ENSO) strongly affects the interannual variations of precipitation in South and East China, its influence on MCSs remains poorly understood. This study examines how ENSO modulates MCSs over China based on satellite observations and reanalysis data during 2001–2020. The influence of ENSO on MCS activity exhibits strong regional and seasonal dependence, with the strongest signals in the Yangtze River region during developing summer and in South China during decaying spring. Along the Yangtze River, MCS activity and associated precipitation decrease during the developing summer of El Niño, but increase during the subsequent decaying summer with a weaker signal. Meanwhile, South China experiences enhanced MCS‐induced precipitation during the decaying spring. The spatial pattern of extreme precipitation difference is broadly consistent with precipitation while exhibiting greater amplitudes. ENSO modulates MCS precipitation by altering MCS frequency, intensity, and duration, but the intensity changes over South China are weaker than those over the Yangtze River. The controlling mechanisms differ between regions. It is revealed that vertical motion dominates the MCS changes in the Yangtze River region, whereas convective available potential energy and moisture dominate those in South China. Along the Yangtze River, the environmental anomalies during the decaying summer of El Niño are weaker than those during the developing summer, consistent with the weaker MCS response.