Properties of Arctic Aerosols based on Photometer Long-Term Measurements in Ny-Ålesund
On the base of sun and star photometer measurements located at the German-French polar research base in Ny-Ålesund (78:923°N, 11:928°E), Svalbard, long-term changes (2001-2017 with focus on 2009-2017) of aerosol properties in the European Arctic are analysed. The main focus were physical aerosol properties like aerosol optical depth (AOD) or Ångström exponent, during the Arctic Haze season in spring compared to summer months. The presence of polar night and day is the limitating factor of available photometer measurement data. To get a full year-round data set a star photometer was also taken into account for the time between October and March. In order to gain more information out of the measurement data of the photometers and to reduce the error of fitting the data to the Ångström law a new ansatz is also discussed in this thesis. With the radiative transfer calculator libRadtran artificial aerosol distributions were created to analyse the information content of real (noisy) photometer data. Indeed it was found that the new ansatz with wavelength dependent Ångström exponent reveals valuable information about the Arctic aerosol. Monthly means of the measured AOD of the years 2009-2017 are compared with monthly means of previous studies to see changes in the properties of aerosol. Additionally, a comparison of sun and star photometer at the same site and the same years is also done. Because photometer data has no height information a comparison with the Lidar is presented. To study possible sources and sinks of aerosol, 5-days back-trajectories were calculated with the FLEXTRA model at three different arriving heights (500m, 1000m and 1500m) at 12 UTC over Zeppelin Station, at Zeppelin mountain 474m above sea level and close to the village NyÅlesund. Beside of the pathway of the aerosol into the European Arctic based on the calculated backtrajectories the influence of the lowermost 100hPa atmospheric layer is also analysed. Especially aerosol is highly affected by cloud formation and is removed out of the atmosphere by precipitation, areas with a high probability of cloud formation is also taken into account.