Summer Mesoscale Convective Systems in Convection-Permitting Simulation Using WRF Over East China

Mesoscale convective systems (MCSs) are active precipitation systems in East China. The increasing frequency and intensity of MCSs highlight the need for better simulation and forecasting. This study conducted a 22-year (2000–2021) JJA simulation at a CP resolution (4-km grid spacing) using the WRF model (WRF-CPM) over East China. The WRF-CPM model's ability to reproduce MCSs was evaluated against satellite infrared-retrieved cloud top temperature, IMERG V06 precipitation, and global reanalysis data ERA5. Results show that WRF-CPM captures the observed MCS frequency and precipitation patterns but overestimates them in most areas, which might be related to the overestimated moisture and CAPE. The model also reproduces the eastward propagation of MCSs, albeit at a slightly faster speed and longer duration. MCSs in WRF-CPM exhibits realistic life cycles in terms of cloud top temperature, convective core area, and precipitation. WRF-CPM tends to overestimate rainfall frequency over 20 mm/hr while underestimates rainfall per MCS, possibly due to an overestimated number and area. The model captures the diurnal cycle of MCSs well in most of East China, though it shows a 2-hr delay in southeast China and produces the peak a few hours earlier to the east of Tibetan Plateau. Total column water vapor (TCWV) and wind shear are well-established factors controlling MCS behavior and rainfall, yet capturing the effects remains a challenge for CP models. This study is the first to show that WRF-CPM can capture the shear effect on MCS precipitation, showing an increase in precipitation with stronger shear and higher TCWV.