大连初冬一次辐射平流雾天气过程分析

摘要

利用大连机场地面观测资料、Micaps系统下常规资料、探空资料和NCEP/NCAR全球再分析资料,从天气形势和背景、探空资料分析和物理量诊断方面,对2009年11月30日-12月2日发生在大连地区持续性大雾天气过程做了详细分析。结果表明,本次持续性雾过程属于辐射平流雾,是在稳定的大尺度天气背景下形成的。探空资料表明,大雾发生过程中,边界层内出现一层逆温和多层逆温;边界层内近地层的逆温和充沛的水汽条件对雾的形成和长时间的维持起着重要的作用。热力结构分析表明,温度日较差大表明地面辐射冷却对本次大雾过程具有明显的作用;低层持续的弱暖平流输入,有利于近地层逆温的建立和维持。动力场结构分析表明,在中低层,大雾发生前期和维持时期,存在弱的辐合上升运动;在大雾消散期,存在明显的辐散下沉运动。水汽条件分析表明,增湿和冷却使此次大雾过程中水汽达到饱和状态产生凝结,在大雾过程的前期,存在弱的水汽辐合;在大雾消散期,存在水汽辐散。%The dynamic and thermal features of a rare radiation advection fog in Dalian that occurred during 30 November and 2 December 2009 are analyzed by using the station observation data in Dalian Airport,sounding data,convection data of MICAPS and NCEP/NCAR reanalysis data.The results show that the heavy fog was of radiation advection type and it occurred in the stable stratification in large scale circulation;the sounding data showed that single or multiple thermal inversion layers occurred in the fog process.The temperature inversion and sufficient vapor were very important for the formation and maintenance of the fog.Analysis of the thermal fields showed that a cooling process produced by net surface radiation fluxes played a key role in the fog.The continuous weak warm and moist advection on lower layers led to the formation and maintenance of the temperature inversion on this layer.Analysis of the dynamic fields showed that the situation of weak convergence and the slightly upward vertical velocity occurred at the beginning and during the maintenance of the fog on the low-altitude layer while weak divergence and the slightly downward vertical velocity occurred during dissipation time.Analysis of the vapor condition showed that reinforcing the humidity and cooling the temperature were both important in the process of bringing in enough vapor to be saturation.Weak convergence of vapor occurred at the beginning of the fog while weak divergence existed during the dissipation time.