Interannual and seasonal variations in the aerosol optical depth of the atmosphere in two regions of Spitsbergen (2002-2018)

In this work, hourly averaged sun photometer data from Barentsburg and Ny-Alesund, both located on Spitsbergen in the European Arctic, are compared. Our data set comprises the years from 2002 to 2018 with overlapping measurements from both sites during the period from 2011 to 2018. For more turbid periods (aerosol optical depth, AOD, tau(0.5) > 0.1), we found that Barentsburg is typically more polluted than Ny-Alesund, especially in the shortwave spectrum. However, the diurnal variation in the AOD is highly correlated. Next, tau was divided into a fine and coarse mode. It was found that the fine-mode aerosol optical depth generally dominates and also shows a larger interannual than seasonal variation. The fine-mode optical depth is in fact largest in spring during the Arctic haze period. Overall the aerosol optical depth seems to decrease (at 500 nm the fine-mode optical depth decreased by 0.016 over 10 years), although this is hardly statistically significant.