西北东部霾的时空特征与天气特征研究

Spatio-Temporal Distribution of Aerosol and Weather Characteristics during Haze over the Eastern Northwest China

利用常规地面观测资料和CALIOP/CALIPSO卫星遥感资料统计分析了中国西北东部霾的多年变化以及霾事件期间气溶胶光学特性的垂直空间分布特征,并以2013年3月和11月发生在西北东部的霾天气为例分析了霾发生时大气气溶胶粒子的形状及大小的垂直分布特征、对应的天气形势和气象要素的变化。结果表明：西北东部霾日出现频率由20世纪80年代至90年代末逐渐减小,但21世纪起又明显增加;霾事件主要发生在11、12和1月。霾发生时,在对流层内霾影响最严重的区域在距地面2～4 km范围,垂直方向气溶胶后向散射系数的范围集中于0.8×10^-3～2.5×10^-3km-1·sr-1,且随高度增加而增大;气溶胶的体积退偏比大部分〈20%,气溶胶较为规则,不规则的多分布在地表向上4 km以下,随着高度的增加气溶胶不规则性减弱。色比数值大部分〈0.8,8～12 km气层中主要是色比为0.0～0.4的粒子。当高空受高压系统控制,地面为均压场,近地面出现逆温层时易产生霾。

More frequency of haze events during recent ten years,caused more and more concern,it is hard to get the comprehensive information only with the ground-based observation.Based on CALIOP/CALIPSO satellite remote sensing data and ground-based routine observations,annual variation of haze events and the vertical spatial distribution characteristics of aerosol optical properties during haze event occurred in the eastern Northwest China（ENWC）was analyzed,to have a deeper understanding of haze events.Taking the haze events occurredin ENWC in March and November 2013 as examples,the aerosol particle shape and size distribution,weathersituation and meteorological elements during haze events were analyzed.The results show that,the frequency ofhaze events in ENWC decreased from 1981 to 2000 firstly and then increased obviously in early 21 th century.Haze events occurred most frequently in December,November and January.When haze events occurred,the majority impact area in the troposphere is from 2 km to 4 km above the surface,the aerosol backscatter coefficientranged from 0.8×10^-3～ 2.5 ×10^-3km-1·sr^-1,and the backscatter coefficient decreased firstly with altitude andthen increased gradually.Aerosols volume depolarization ratio was mostly less than 20% in the area,whichmeans most part of aerosols were regular particles.The irregular particles were suspending under 4 km above thesurface the aerosol irregularities were weaken with the increasing of altitude.The value of Color ratio was below0.8 in the area and centered at 0.0 ～ 0.4 between 8 and 12 km in height.Haze events could easily occur when thehigh-altitude and the surface are separately controlled by high-pressure system and uniform pressure,and there istemperature inversion near surface.This work provides advanced method for haze research and may contribute to the improvement on the prediction accuracy of heavy polluted weather.