北京市秋冬大气污染传输特征遥感研究

综合地基遥感、卫星遥感与地面监测数据对北京市2016年10月—2017年3月的污染来源及传输特征进行分析,并结合气象数据对污染形成的气象条件进行研究.结果表明,冬季重污染发生频率最高,2016年12月和2017年1月发生频率均超过30%.平缓型污染以本地来源为主,单峰型和多峰型污染由本地污染与区域传输共同导致.平缓型和单峰型本地污染集中在北京中南部,多峰型扩散至全市.区域传输方向均以西南为主,单峰型和多峰型存在东南传输.单峰型以1次传输为主,多峰型均为多次传输.传输层的高度差异较大,但均在0.3～0.5 km高度存在低空传输层,并且存在高于1.0 km的高空传输.平缓型、单峰型和多峰型污染的垂直延伸高度分别为0.5、0.7和1.0 km.研究污染发生时的气象条件,发现污染发生时风向均以西南风为主,发生频率高于60%,其次为东南风.相对湿度和消光系数随污染等级提升逐渐升高,当相对湿度高于70%时,多峰型污染消光系数高于2.0 km~(-1)的频率达到63.33%.3种类型污染发生时的逆温频率均高于75%,高强度的贴地逆温是造成本地污染的成因之一.

Analysis of characteristics of air pollution transmission in fall and winter by remote sensing in Beijing

Air pollution sources and their transmission characteristics in Beijing from October 1, 2016 to March 31, 2017 were investigated by the information obtained from ground-based remote sensing, satellite remote sensing and ground monitoring. The relationship between meteorology and air pollution was explored combining with the meteorological observation. The analysis shows that the highest frequency of heavy pollution occurred in winter, with average frequency of over 30% in December and January. Local emission was the major source of gentle type pollution, while local emission and regional transmission contributed to the single peak and multi peak jointly. Local emission, demonstrated by gentle type and single peak, concentrated in central and south of Beijing. Multi peak pollution spread to the whole city. Regional transmission was mainly from southwest, and there was southeast transmission in single peak and multi peak pollution. The single peak pollution was mainly single transmission, and the multi peak one was the result of multi-transmission. The composition of transport layer were various, with a low altitude layer in 0.3~0.5 km, and a high altitude layer above 1.0 km in common. The vertical extension height of gentle type, single peak and multi peak pollution were 0.5, 0.7 and 1 km, respectively. The analysis of meteorological conditions exhibits that air pollution often occurred in southwest wind, the occurrence frequency was higher than 60%, followed by southeast wind. The relative humidity and extinction coefficient increased gradually with the pollution level. The frequency of multi peak pollution extinction coefficient over 2.0 km^-1 reached 63.33% when the relative humidity was more than 70%. The frequency of inversion was higher than 75% when the 3 types of pollution occurred, indicating the high intensity of ground inversion being one of the causes of local pollution.