中文摘要：

利用非静力中尺度模式MM5V3对2009年11月30日到12月1日天津武清地区的一次大雾天气过程进行了数值模拟研究,这次大雾过程主要分布在天津、河北、山东地区,天津市武清县位于大雾的边缘位置。此次雾过程可以分为3个阶段。11月30日的17：00（北京时间,下同）至12月1日00：00是雾的形成阶段,12月1日00：00出现雾,00：00至09：00是雾的发展阶段,09：00之后是雾的消散阶段。模拟研究表明长波辐射降温使得温度下降并导致逆温层出现,同时由于暖湿气流输送,观测点处具有充足的水汽供应,促使了大雾的形成;在雾形成之后,逆温层的维持、持续的长波辐射降温有利于雾的不断发展;而后期辐散下沉运动明显,水汽不断向外辐散,使得雾逐渐消散。湍流对雾的影响是向上和向四周传输水汽,使得雾范围扩大,但如果太强,又会使得雾很快消散。

英文摘要：

The NCAR/PSU MM5v3 model is used to simulate a fog event in the Wuqing area from 30 Nov to 1 Dec 2009. This severe fog was distributed mainly in Tianjin, Hebei, and Shandong; Wuqing was at the edge of the fog area. This fog event can be seen as having three phases： After the formation phase from 1700 LST 30 Nov to 0000 LST 1 Dec, fog began to form at 0000 LST 1 Dec. The development phase lasted from 0000 LST to 0900 LST; after 0900 LST the fog began to disperse. With a cooldown caused by long-wave radiation cooling, an inversion appeared; in addition, sufficient water vapor was transferred by a warm wet flow. Weak convergent upward motion occurred in the surface layer. Under these conditions, fog formed. The maintenance of the inversion and sustained long-wave radiation cooling is conducive to continuous fog development. In the third phase, fog began to dissipate as a result of vapor divergence. Turbulence transfers water vapor, but if the turbulence is too strong, fog will dissipate quickly.