Impacts of the Decadal Urbanization on Thermally Induced Circulations in Eastern China

Significant urbanization has occurred in the Yangtze River Delta region of eastern China, which exerts important effects on the local thermally induced circulations through regulating the heat flux and thermal structure. Previous studies lack a correct representation of the seasonal vegetation phenology associated with urban expansion, and therefore it is difficult to accurately describe the land-atmosphere coupling. In this study, high-resolution Moderate Resolution Imaging Spectroradiometer (MODIS) observations are used to describe the changes in land surface characteristics, including land-cover type, green vegetation fraction, and leaf area index with the Weather Research and Forecasting Model. The use of MODIS satellite observations provides a clear improvement in model performance when compared with ground-based measurements. Atypical urban heat island is generated around Shanghai, Wuxi-Suzhou-Yangzhou, and cities along the Yangtze River and Hangzhou Bay, which subsequently modifies the local thermal circulations. The sea breeze is significantly enhanced over the north bank of Hangzhou Bay because of the increased land-sea temperature contrast. Several surface convergent zones are generated along the Shanghai-Suzhou-Wuxi city belt as a result of the combined effects of the urban heat island, the enhanced sea breeze, and the lake breeze at Lake Tai.