北京一次大雾天气成因分析及模式预报性能检验

Analysis of Heavy Fog Process and Model Prediction Test in Beijing

为了研究空气中水汽层结变化、大露天气发生发展的环境场紊件及BJ-RUC模式在大雾期间的预报性能，对北京2012年3月16～17日大雾天气个例中能见度变化和地基微波辐射计液态水含量等资料进行分析。结果表明，雾生消前后液态水含量的廓线变化明显，因此通过不同时刻液态水舍量的廓线对比分析，对大雾天气的预报还是具有指示意义的；地面高压底部偏东风为大雾维持提供良好的水汽，大雾期间风力的加大有利于水汽的输送，而持续的偏东风则有利于水汽的维持；辐射降温触发了华北雾区的形成；逆温层的存在是此次大雾发生的条件之一；近地面层系统性的偏东风、相对湿度和温度均在BJ—RUC模式中有很好的反映，模式探空的预报随着起报时间的临近，越接近实况，特别是逆温层和近地面偏东风的预报与实况基本一致，由此导出产品的能见度预报也能给预报员很好的指示参考性。

To study the effects of the stratification changes of water vapor, the variation of visibility relative to the liquid water content and rel- ative humidity observed by microwave radiometer and forecast of the visibility by BJ-RUC during fog events from March 16 to 17, 2012 in Bei- jing was analyzed. The sequence diagram results showed that the various times in the profile diagram of atmospheric liquid water content can indicate the presence of fog because the stratification of liquid water content obviously changes during the generation and dissipation of fog. East wind of high pressure bottom advantage to water vapor to maintain and the increase of wind advantage to water vapour transportation to Beijing, radiation cooling trigger fog in North China Plain, and inversion layer is one of the condition. East wind of the surface layer, relative humidity and temperature have very good response in Bj-RUC. Air sounding forecast close to actually along with the time, especially to tem- perature inversion and east wind of surface layer. Therefore product visibility can give indication and reference to forecaster.