Assessing the added value of convection-permitting modeling for urban climate research: A case study in eastern China

Accurate urban-resolving climate data are essential for urban climate research and applications. However, General Circulation Models (GCMs) often lack the resolution and urban representation needed to provide reliable fine-scale climate information over urban areas. Convection-permitting modeling (CPM) has emerged as a promising solution to this challenge, despite its computational demands. Evaluating the added value of CPM for specific regions is crucial. In this study, we utilized the Weather Research and Forecasting (WRF) model coupled with a single-layer urban canopy model, as a regional climate model, to assess the performance and added value of CPM at both regional (urban clusters) and local (megacity) scales. With an optimized dynamic downscaling scheme, we conducted 3-km-resolution CPM and 9-km-resolution dynamic downscaling modeling (DDM) during the summer of 2020 in eastern China, where most cities and urban clusters are located. At the local scale, CPM well reproduced observed precipitation rates at daily and sub-daily time scales, greatly improved the overestimation of drizzle-to-light rainfall events and underestimation of heavy-to-torrential rain events in ERA5 reanalysis data. Additionally, CPM effectively captured diurnal variations in precipitation across six sub-regions of eastern China, a capability lacking in DDM and ERA5. Moreover, CPM successfully reproduced the observed urban heat island intensity in Beijing by capturing the heterogeneous air temperature distribution, outperforming ERA5 and DDM. Our findings highlight the considerable added value of CPM in simulating sub-daily precipitation variations and urban heat island intensity over urban areas of China. These insights will greatly enhance future high-resolution regional climate simulations and climate change projections over urban areas in China.