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Potential sensitivity of warm season precipitation to urbanization extents: Modeling study in Beijing‐Tianjin‐Hebei urban agglomeration in China
Author(s) -
Wang Jun,
Feng Jinming,
Yan Zhongwei
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2015jd023572
Subject(s) - urbanization , beijing , urban climate , urban agglomeration , environmental science , china , geography , impervious surface , precipitation , population , urban heat island , climatology , physical geography , economic geography , meteorology , economic growth , ecology , demography , archaeology , sociology , geology , economics , biology
In this study, we investigated how different degrees of urbanization affect local and regional rainfall using high‐resolution simulations based on the Weather Research and Forecasting Model. The extreme rainfall event of 21 July 2012 in Beijing was simulated for three representative urban land use distributions (no urbanization, early urbanization level of 1980, and recent urbanization level of 2009). Results suggest that urban modification of rainfall is potentially sensitive to urban land use condition. Rainfall was increased significantly over the downwind Beijing metropolis because of the effects of early urbanization; however, recent conditions of high urban development caused no significant increase. Further comparative analysis revealed that positive urban thermodynamical effects (i.e., urban warming, increased sensible heat transportation, and enhanced convergence and vertical motions) play major roles in urban modification of rainfall during the early urbanization stage. However, after cities expand to a certain extent (i.e., urban agglomeration), the regional moisture depression induced by the prevalence of impervious urban land has an effect on atmospheric instability energy, which might negate the city's positive impact on regional rainfall. Additional results from regional climate simulations for 10 Julys confirm this supposition. Given the explosive urban population growth and increasing demand for freshwater in cities, the potential negative effects of the urban environment on precipitation are worth investigation, particularly in rapidly developing countries and regions.