长沙市灰霾天气与气象因子相关性研究

根据长沙市2013年PM2.5的逐日质量平均浓度、气象地面和高空观测数据,采用SPSS方法,分析了长沙市灰霾天气发生与气象因子的关系。结果表明:长沙市区的灰霾日以西北风向为主,PM2.5浓度与风速、降水呈显著负相关,与相对湿度、大气压、平均气温相关不明显。风速越小越不利于大气污染物的扩散,在没有降水的情况下,风速达到3.5m/s以上,空气质量才有好转;弱降水对污染物的浓度不会有明显的影响,降水量在5mm以下时,污染物的浓度不会有明显的下降,但强降水对空气有净化作用明显,在不同季节,不同时段,不同天气形势下降水的稀释作用不同;长沙秋冬季边界层稳定性几率高达80%以上,这种稳定层结构是长沙市区各种大气污染源不易扩散的重要因素之一。

The Research of Correlation Between Dust-haze and Meteorological Factors in Changsha

According to daily average mass concentration of PM2. 5 and the meteorological observed data of ground and air, this paper analyzed the correlation between dust-haze and meteorological factors in Changsha by the method of SPSS. The analysis results indicated that the northwesterly winds were prevailing in the dust-haze days in Changsha urban area. There is abvious negative correlation between PM2. 5 concentration and wind velocity and rainfall, no significant correlation with relative humidity, barometric pressure and mean temperature. The slower the wind velocity is, the harder atmospheric pollutants can spread. Without precipitation, air quality would not improve untill wind speed reaches 3.5 meter per second. Light rainfall will not have noticeable impact on the concentration of atmospheric pollutant, which won＇t decrease when the precipitation is less than 5ram. But heavy rainfall can apparently clean up the atmosphere and improve air quality. The dilution effect of rainfall is different in different season, different period and different weather situations. In the autumn and winter, the boundary layer of Changsha has 80 percent chance of being stable. This stable structure is an important factor that makes urban atmospheric pollutant not spread easily.