The impacts of future urban development and global warming forcing on hourly extreme rainfall over the Pearl River Delta (PRD) area have been investigated, by dynamically downscaling General Circulation Model (GCM) outputs using the Weather Research and Forecasting Model (WRF) at convection-permitting resolution, coupled with an Urban Canopy Model (UCM). Three downscaling experiments corresponding to different urban land cover (1999 and projected 2030) and climate (1951-to-2000 and 2001-to-2050

more »

... GCM simulations) were designed. Near-future climate change (up to 2050) and 1999-to-2030 urban development effects on PRD extreme precipitation were then examined. Results show that climate change and rapid urban development forcing have comparable positive effects on the intensity as well as heavy hourly rainfall probability over the PRD megacity. Global warming tends to increase heavy rainfall probability (from 40 to 60mm/hr) by about 1.3 to 1.8 times, but suppresses the frequency of light rainfall. Urban development increases urban rainfall probability within the whole range of intensity, with frequency for very heavy rainfall (> 90mm/hr) almost doubled. Overall, forcing due to rapid urban development plays an important role for projecting rainfall characteristic over the highly urbanized coastal PRD megacity, with impacts that can be comparable to global warming in the near future.