西安市城市气溶胶污染岛长时间序列特征分析OA北大核心CHSSCDCSTPCD

Urban aerosol pollution island(UAPI)has significant impacts on human health,urban thermal environment,urban climate,atmospheric radiation transmission,etc.In this paper,the PM2.5 data of multiple stations in Xi'an from 2016 to 2019 were used to quantitatively calculate the intensity of UAPI,and then the daily and annual variations of PM2.5 and the intensity of UAPI were analyzed.Additionally,the empirical mode decomposition(EMD)method was employed to analyze the multi-scale characteristics of the long-term time series of UAPI intensity.The results show that there was obvi-ous urban aerosol pollution island effect in Xi'an,and the proportion of UAPI intensity greater than 10 μg/m3 reached 87.63%.In terms of intraday variations,UAPI intensity exhibited a characteristic of being higher at night and lower during the day time;in the annual variations,a"U"-shaped distribution was observed with higher values in winter and spring,and lower values in summer and autumn.On an interannual scale,the UAPI effect showed a gradual weakening trend from 2016 to 2019.The EMD decomposition can effectively reveal the multi-scale characteristics of UAPI intensity,such as IMF2,IMF4,and IMF6,which respectively reflect the characteristics of UAPI intensity with weekly,monthly,and annual cycles.By comparing PM2.5 time series with UAPI time series,this study can be helpful for the effective elimination of the influence of cross regional transmission pollution and large-scale secondary pollution on the intensity of UAPI.