Atmospheric water budget associated with a local heavy precipitation event near the Central Urban Area of Beijing Metropolitan Region

摘要

An isolated storm-triggered heavy precipitation event near the Central Urban Area (CUA) of Beijing on 9 August 2011 was simulated using a cloud-scale simulation. The atmospheric water budgets in both the initiation area (TA area) and the heavy rainfall region over the CUA (UAS area) associated with the storm were investigated using the three-dimensional (3D) precipitation equation, respectively. The main results showed that the moisture-related rate (QWV) largely offset the hydrometer-related rate (QCM) in both areas, which is different from the previous studies on topographic rainfall and tropical cyclone rainfall. The magnitudes of the precipitation equation related terms were generally more prominent in the UAS area than the TA area, followed by heavier precipitation rate (PS) in the UAS area, due to stronger upward motion contributed by the mature of the system in the former area. Moreover, the initiation, development and movement of the storm also resulted in different vertical dynamic structures in the two areas. And the differences of vertical dynamic structures and their evolutions triggered different water vapor and hydrometeor budgets in these two contiguous areas. Analysis of vertical profiles of hydrometeors in both areas further confirmed the above conclusions.