上海一次连续大雾过程的成因分析

利用上海市遥测能见度数据、常规气象资料和T213、GFS分析资料以及GPS-PWV资料,分析了2008年1月5-11日发生在上海地区的一次连续大雾天气过程.分析表明当有天气尺度西风槽频繁活动、槽前暖湿气流不断向气层输入暖湿空气,如再遇特定暖水面或暖海面从近地面向气层输送暖湿气流时,在晴天和微风的早晨极易形成辐射雾；当东、黄海暖湿空气从近地面流向冷水面或冷陆面,如再遇江南低空偏南暖湿气流辐合聚积时,极易形成平流雾.雾区登陆距离与东风气流强弱有关,东风气流越强,雾区西进距离越长.在平流雾期间,0～300 m平均相对湿度的高湿区与雾区吻合.当绝对湿度小于3 g/kg时不会有大雾发生,绝对湿度在9～1 5 g/kg和GPS-PWV值在15 mm左右时,在合适的大气条件下容易形成大雾.

Causal Analysis of a Continuous Dense Fog in Shanghai

The continuous fog process from January 5 to 11 2008 in Shanghai is analyzed using remote sensing visibility and conventional observation, GFS and T213 model, and GPS PWV data. The results show when there are frequent synoptic scale troughs moving east and warm moist air flow in front of the troughs, it is easy to form radiation fog in sunny and breezing morning, in addition with warm moist air near the surface layer from warm water or sea surface. When warm moist air near the surface layer flows from the East China Sea or the Yellow Sea to cold water or land surface, it is also easy to form advection fog, in addition with the convergence of the low level southerly warm moist air from the south of the Yangtze. The range of advection fog from sea is closely related to the strength of easterly air flow. The stronger the easterly air flow is, the longer the advection fog would moves. The research also shows that the area with high average relative humidity within 0 to 300 m above the surface is consistent with the fog zone during the advection fog period. When absolute humidity is less than 3 g/kg, there would be no fog forming. While absolute humidity is between 9 and 15 g/kg and the GPS PWV is about 15 mm, the probability of thick fog would be high under appropriate weather condition.