Impact of city belt in Yangtze River Delta in China on a precipitation process in summer: A case study

The Weather Research and Forecasting (WRF) model was used to investigate the influence of city belt in the Yangtze River Delta (YRD) in China on a summertime rainstorm process. The comparisons for simulations with and without the presence of the urban areas show that the increase in precipitation mainly occurs downwind of the city belt, while the increases and decreases in precipitation represent as adjacent belts in the main precipitation belt. It was found that the downstream propagation of the urban heat island (UHI) signal alters the general circulation pattern, thermal distribution and moisture transportation at local and regional scale. The variation in accumulated rainfall is in excellent correspondence with the changes in the atmospheric dynamic and thermodynamic property associated with the downstream propagation of the UHI signal, suggesting that the variations in precipitation resulting from the effect of scattered urban clusters can be strongly related to this downstream propagation of the UHI signal. The “chain flow”, generated by the combination of the sea-breeze–heat-island circulations over the coastal urban areas and the heat-island circulation over the inland urban areas, should also make a contribution.