长江三角洲背景地区大气污染对能见度的影响

Impacts of atmospheric pollution on visibility in the background area of Yangtze River Delta,China

通过分析2008~2015年临安区域大气本底站在线观测能见度,研究长江三角洲背景地区能见度的时间变化特征及影响因素,尝试建立长江三角洲能见度特征值的筛选方法,探讨长三角能见度的区域特征值,评估人为源排放对能见度的影响程度.结果表明,临安站能见度的日变化分布表现为单峰型形态,与相对湿度的日变化分布呈显著负相关;季节变化特征表现为春夏季较高,秋冬季较低,主要受到大气污染季节变化的影响;2008~2015年临安站春、夏季能见度的年增长幅度较大,秋冬季则保持稳定.高相对湿度、高污染是造成临安地区低能见度的重要因素.结合气象要素和大气污染物排放建立能见度特征值的筛选方法,得到长三角背景地区的能见度特征值为(9.7±2.2)km,人类活动的影响将导致能见度下降约4.4km.

Temporal trend of visibility and factors affecting it in the background area of Yangtze River Delta(YRD)were studied based on in-situ observation at Lin’an regional atmospheric background station from2008to2015.A new extraction method was developed in order to obtain the regional background visibility in YRD and assess the impact of human activities on it.The results revealed that the diurnal variation of visibility presented a single peak at Lin'an station,with the lowest value observed at dawn and the highest in the afternoon,respectively;besides,the diurnal variation of visibility showed a negative correlation with that of relative humidity.The seasonal variation of visibility appeared to be mainly influenced by atmospheric pollution,which presented higher value in spring and summer,and lower value in autumn and winter.In addition,from2008to2015,the annual growth rate of visibility had a significant increase in spring and summer while maintained at a stable level in autumn and winter.The statistical analysis showed that high relative humidity and severe air pollution were two important factors for low visibility at Lin'an station.The new extraction method was established based on the observations of both air pollutants and meteorological conditions.The daily average regional background visibility in YRD was9.7±2.2km,which appeared to be affected significantly by anthropogenic emissions,and decreased by4.4km compared to the regional natural visibility.