High-Resolution Hindcast of Record-Breaking Rainfall in Beijing and Impact of Topography

In this paper, a hindcast study of the record-breaking rainfall event occurring in Beijing on 21 July 2012, is conducted by using the Weather Research and Forecasting (WRF) model forced by National Centers for Environmental Prediction (NCEP) Global Forecasting System (GFS) outputs, paired with an investigation of the impact of topography in this region. The results indicate that WRF can reasonably predict the salient features of orographic precipitation; the 24-h rainfall amount and spatial distribution compare reasonably well with the observations. The hindcast simulation also indicates that rainfall events can be predicted approximately 36 h ahead. When the topography is removed, the spatial distribution of rainfall changes remarkably, suggesting the importance of the topography in determining rainfall structure. These results also indicate that prediction of such city-scale heavy rainfall events would benefit from a high-resolution prediction system.