安徽沿长江东部春季一次大范围雾天气过程诊断分析

摘要

Using surface observed data,upper sounding data,NCEP reanalysis data,wind profile radar data and me-teorological station data along the motorway in Wuhu,the circulation and physical conditions about formation and dissipation of a fog process on March 6,2012 along the eastern Yangtze river in Anhui province were analyzed. The results show that this spring fog process belongs to radiative fog.There are mainly westerly to southwesterly winds over the fog area when the heavy fog occurs,without significant cold air.It is controlled by the equal high pressure field in Anhui province,so it is beneficial to the formation and maintenance of fog.The physical condi-tions about formation and dissipation of the fog show that enough water vapor and moisture condensation caused by long wave radiative cooling are important reasons of the heavy fog formation.The inversion layer formed by ra-diative cooling near the ground benefits the maintenance of fog,and the fog becomes thicken and develops with ris-ing of the inversion layer near the ground.Stability stratification formed by the inversion layer of low level pre-vents moisture transports upwards.Low wind speed near the surface,weak vertical shear of wind in middle and low atmosphere,turbulence in low layer,no obviously ascending motion in middle atmosphere,these all constitute the favorable dynamical conditions of fog formation,and they can make the wet layer thickened and prevent moisture transport upwards,which is also beneficial to formation and maintenance of fog.After sunrise,the solar radiation becomes stronger,and conditions beneficial to formation and maintenance of fog like radiation cooling,inversion layer and dynamical conditions disappear,so the fog dissipates.%利用地面气象观测资料、高空探测资料、NCEP再分析资料、芜湖市边界层风廓线雷达资料和高速公路气象观测站资料，分析了2012年3月6日安徽省沿长江东部大范围雾天气过程形成的环流背景及雾生消的物理条件。结果表明：安徽沿长江东部地区此次春季大范围雾的性质为辐射雾，雾发生时雾区上空以西到西南风为主，无明显冷空气影响，地面为高压控制的均压场，有利于雾的生成和维持。由雾生消的物理条件可知，近地面水汽条件较好和长波辐射降温造成的水汽凝结是此次大范围雾形成的重要原因。地面辐射降温形成的近地面逆温层有利于雾的维持，且随着近地面逆温层的抬升，雾层变厚并发展。低空的逆温层则形成稳定的层结，阻止水汽向上传输。近地面风速大小合适，风垂直切变小，低层有湍流，中层无明显上升运动，构成雾形成的有利动力条件；使湿层变厚的同时也阻止了水汽向高层交换，有利于雾的生成和维持。日出后，太阳辐射增强，有利于雾发生和维持的地面辐射降温、逆温和动力条件逐渐消失，雾逐渐消散。