Convection-permitting regional climate simulation of warm-season heat extremes over Eastern China

Abstract:

In a warming climate, increasing heat extremes (HEXs) have been observed worldwide, leading to the increasing number of deaths caused by heat waves. The convection-permitting modeling (CPM) has been applied over several regions of the world to enhance the fidelity of regional climate modeling and projection. In this study, we perform CPM simulations using the Weather Research and Forecasting (WRF) model over the densely populated Eastern China for ten warm seasons (2008-2017), and evaluate its skill in capturing the HEX characteristics. To examine the urban-rural contrast of the HEX characteristics, we classify stations based on the land use/land cover data in 2010 and 2015 for the earlier and later halves of 2008-2017, respectively. The study region is divided into 2.5º×2.5º latitude-longitude grids.

Results show the CPM generally underestimates the occurrence frequency, duration, and intensity of the independent hot days (IHD) and the compound events (extremely hot days during both daytime and nighttime) at both urban and rural sites in most grids, because of a negative bias of the daily maximum temperature (Tmax) in most grids. The observations suggest a clear urban heat island (UHI) effect on the compound events, which is captured by the CPM. The CPM tends to overestimate the total number of independent hot nights (IHN), especially at the urban sites, due to the longer duration of the simulated IHN events than the observation. The dependence of the simulated HEX characteristics on the physical parameterization schemes is also examined, focusing on representation of aerosol effects, subgrid cloud fraction, and urban canopy model.