Impacts of Urban Processes and Urbanization on Summer Precipitation: A Case Study of Heavy Rainfall in Beijing on 1 August 2006

Finescale simulations (with 500-m grid spacing) using the Weather Research and Forecasting Model (WRF) were used to investigate impacts of urban processes and urbanization on a localized, summer, heavy rainfall in Beijing. Evaluation using radar and gauge data shows that this configuration of WRF wi...

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Bibliographic Details
Published in:	Journal of applied meteorology and climatology 2011-04, Vol.50 (4), p.806-825
Main Authors:	Miao, Shiguang, Chen, Fei, Li, Qingchun, Fan, Shuiyong
Format:	Article
Language:	eng
Subjects:	Aerosols Bifurcations Cities Climate models Convective cells Data assimilation Data collection Earth, ocean, space Exact sciences and technology External geophysics Heating Heavy rainfall Land use Maximum rainfall Meteorology Meteors Metropolitan areas Modeling Momentum Momentum transport Precipitable water Precipitation Radar Radar data Rain Rainfall Rainfall amount Sensitivity Sensitivity analysis Simulation Squalls Storms Studies Summer Summer precipitation Transport Urban areas Urbanization Weather Weather forecasting
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Summary:	Finescale simulations (with 500-m grid spacing) using the Weather Research and Forecasting Model (WRF) were used to investigate impacts of urban processes and urbanization on a localized, summer, heavy rainfall in Beijing. Evaluation using radar and gauge data shows that this configuration of WRF with three-dimensional variational data assimilation of local weather and GPS precipitable water data can simulate this event generally well. Additional WRF simulations were conducted to test the sensitivity of simulation of this storm to different urban processes and urban land-use scenarios. The results confirm that the city does play an important role in determining storm movement and rainfall amount. Comparison of cases with and without the presence of the city of Beijing with respect to the approaching storm shows that the urban effect seems to lead to the breaking of the squall line into convective cells over the urban area. The change of precipitation amount depends on the degree of urbanization (i.e., the change over time in the extent of Beijing city). Model results show that an early urbanization prior to 1980 decreases the maximum rainfall, whereas further urbanization in Beijing is conducive to bifurcating the path of rainfall. According to sensitivity results with a single-layer urban canopy model, the thermal transport (sensible and latent heating) induced by the presence of an urban area apparently is more important than associated momentum transport, with latent and sensible heating apparently having equally important roles in the modification of simulated precipitation. Urban surfaces tend to cause the rainfall to be more locally concentrated. High-rise urban cores may bifurcate the path of rainfall as well as increase the area percentage of heavy rainfall.
ISSN:	1558-8424 1558-8432