利用雷达、自动气象站、飞机观测(AMDAR)和探空等多种观测资料, 采用中尺度数值预报模式WRF和资料同化系统ADAS, 对2011年7月31日上海局地强对流过程进行了快速更新同化数值试验.结果表明, 数值试验模拟降水的发生时间、落区和随时间演变与实况基本一致, 较好再现了海陆热力差异导致上海南北两支海陆风爆发、形成低层辐合线, 在热岛效应的叠加下进一步增强, 继而引发局地强对流的过程.快速更新同化技术可有效延长此次过程的预警时效, 这为城市强对流业务预报提供了新的思路.
Using multi-source observations, such as Doppler radar, AWS, AMDAR and radiosonde measurements, and the high-resolution numerical model WRF as well as the advanced data assimilation system ADAS, a numerical simulation of the server convection event, which occurred in Shanghai on 31 July 2011, was conducted using rapid refresh technique. The results showed that the model correctly predicted this server convective weather process, the timing and location, as well as the variation of the precipitation along with the time were well consistent with the observations. It was also found that due to the thermal difference between land and sea, two sea breeze from different north and south directions met in shanghai area and low level convergence line formed, as a results, weak updraft in boundary layer appeared, combined with the local urban heat island effect, created favorable conditions for triggering the server convections; and the high gradient of moisture between low level and middle level and its unstable vertical structure provided favorable conditions for moisture vertical transportation. The numerical simulation using rapid refresh technique issued early warning of this server convection occurrence 10 hours in advance, and this provided a new way for the megacity operational convection forecasts.
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