济南一次雾过程的数值模拟试验和成因分析

基于中尺度天气研究与预报(Weather Research and Forecast,WRF)模式并选取T639模式数据作为初始条件和边界条件,对2015年11月13日至14日发生在济南的一次大雾天气进行数值模拟试验。利用常规观测资料对模拟效果进行检验分析,从不同方面分析这次雾的成因。结果表明:1稳定的大气层结、微弱的风速、较小的温度露点差为雾的形成提供了有利的气象条件;2WRF模式能够较好地模拟出雾形成和发展过程并且可以较为准确地模拟出能见度的强度;3近地层中性层结和较为充足的水汽对雾的形成和发展有重要作用;低云的存在推迟了白天雾的消散;4在雾形成和发展阶段,925hPa以下为辐合上升运动,之上为辐散下沉运动,这使得水汽集中在近地层,有利于雾的生成;5近地层的冷平流会增大相对湿度,是雾形成的有利条件;非绝热因子对这次雾的形成发展并没有起到关键作用。

Numerical Simulation and Cause Analysis of a Fog Event in Jinan

Based on the WRF (Weather Research and Forecast) model and T639 data as the initial and boundary conditions, a fog process in Jinan from 13 to 14 in November 2015 is simulated. The result of simulation test is verified by the routine meteorological observation data, and the causation of the fog is analyzed from four respects. The results show: (1) the stable atmospheric layer, gentle wind, small difference between temperature and dew point are the favorite conditions for the formation of fog; (2) the occurrence and development of the fog as well as the intensity of visibility can be simulated by the WRF model; (3) the maintenance of the neutral layer and enough moisture play the key part for the formation and development of the fog; the low clouds have effect on the formation of the neutral layers near the ground and postpones the dissipation of the fog in the daytime; (4) during the formation and development of the fog, the convergence ascending motion below 925 hPa and divergence sinking motion above 925 hPa can be favorable to the formation of the fog by making the moisture accumulate in the surface layers; (5) the cold advection can be beneficial to the fog formation by increasing relative humidity, while the advection below 850 hPa get warmer in the dissipation phase of the fog, the non adiabatic factor have little impact on the formation and development of the fog.