西安市霾天气与清洁天气变化特征及影响因素分析

Characteristics of haze and clean weather and their influencing factors in Xi'an

利用2006—2012年西安市污染物质量浓度及气象站逐时地面风场、相对湿度和能见度等资料,依据霾天气的定义统计理论霾日数,对比人工观测霾日与判据统计理论霾日的合理性,通过对霾天气与清洁天气过程的气象条件进行分析,探讨西安市霾天气与清洁天气过程的变化特征及影响因素。结果表明:2006—2012年西安市霾天气过程在干季发生频率较高,湿季发生较少。地面风场对霾天气过程影响较大,绝大部分霾天气过程的日平均风速<1.5 m·s-1;干季大部分霾天气过程日平均风速≤1.0 m·s-1,极端个例日平均风速甚至在0.5 m·s-1以下。清洁天气过程在干季发生次数多于湿季,主要与干季风速较大和相对湿度较小相关。

Using pollution data,hourly surface wind,humidity and visibility in Xi′an from 2006 to 2012,the num-ber of haze days calculated by theoretical prediction and observation were compared.Characteristics of haze days and clean days were analyzed,and corresponding meteorological elements were discussed.The results show that frequency of haze days is high in dry season and low in wet season.Effect of the surface wind on the haze weather is significant,and average daily surface wind is below 1.5 m·s -1 in most haze weather.It is equal or less than 1.0 m·s -1 in dry season,and even less than 0.5 m·s -1 in an extreme case.The number of clean days is higher in dry season than in wet season,which is due to the strong wind speed and low humidity in dry season.