Appropriately representing convective heating is critical for predicting catastrophic heavy rainfall in 2021 in Henan Province of China

Abstract

An unprecedented heavy rainfall event occurred in Henan Province of central China during 19–20 July 2021 with the maximum hourly rainfall rate of 201.9 mm, which broke the historical record in mainland China. To investigate the impacts of predicted atmospheric circulation on the regional convection-permitting prediction of this event, two sets of nested experiments with different convective parameterizations (GF and MSKF) in the outer domain and at convection-permitting resolution in the inner domain are performed with the Weather Research and Forecasting (WRF) model. The analysis found the prediction of ‘21.7’ rainstorm at convection-permitting resolution in the inner domain is largely affected by convective scheme in the outer domain. The atmospheric circulation forcing from the outer domain with different convective schemes is significantly different, which ultimately affects the regional synoptic pattern and precipitation in the refined region through lateral boundary forcing. The difference in regional prediction at convection-permitting resolution can be mitigated by adjusting convective latent heat parameterization in the outer domain. This work highlights that appropriately parameterizing convective latent heat is the key to provide reasonable large-scale forcing for regionally predicting this catastrophic heavy rainfall event at convection-permitting resolution, which may also be applicable to other events and other regions.