A multi-year comparison of PM2.5 and AOD for the Helsinki region

作者：Natunen Antti^*; Arola Antti; Mielonen Tero; Huttunen Jani; Komppula Mika; Lehtinen Kari E J

来源：Boreal Environment Research, 2010, 15(6): 544-552.

We studied the relationship between satellite-based aerosol optical depth (AOD) and particulate matter (PM2.5) which is aerosol mass concentration measured on the ground. PM2.5 data originated from four sites located near each other within the Helsinki region, Finland. Depending on the site, the data covered between two and seven years. We investigated how temporal PM2.5 averaging affects the correlation between PM2.5 and AOD. In addition, we studied the seasonality of the correlation. The time-averaging increased the correlation coefficient as compared with one-hour PM2.5 measurements. Regarding the monthly averages of PM2.5 and AOD, the correlation coefficients were between 0.57 and 0.91. We also studied PM2.5 and AOD gradients between an urban and a rural site. Monthly averages at the urban site were regularly higher than those at the rural site. However, the seasonal behaviour was similar.