Justyna Lisok

Impact of North American intense fires on aerosol optical properties measured over the European Arctic in July 2015

In this paper impact of intensive biomass burning (BB) in North America in July 2015, on aerosol optical and microphysical properties measured in the European Arctic is discussed. This study was made within the framework of the Impact of Absorbing Aerosols on radiating forcing in the European Arctic (iAREA) project. During the BB event aerosol optical depth (AOD) at 500 nm exceeded 1.2 in Spitsbergen and 0.7 in Andenes (Norway). Angstrom Exponent (AE) exceeded 1.4 while the absorbing Angstrom Exponent (AAE) varied between 1 and 1.25. BB aerosols were observed in humid atmosphere with a total water vapor column between 2 and 2.5 cm. In such conditions aerosols are activated and may produce clouds at different altitudes. Vertical structure of aerosol plumes over Svalbard, obtained from ceilometers and lidars, shows variability of range corrected signal between surface and middle and upper troposphere. Aerosol backscattering coefficients show values up to 10 -5m-1sr-1at 532 nm. Aerosol surface observations indicate chemical composition typical for biomass burning particles and very high single scattering properties. Scattering and absorption coefficients at 530 nm were up to 130 and 15 Mm-1, respectively. Single scattering albedo at the surface varied from 0.9 to 0.94. The averaged values over the entire atmospheric column, ranged from 0.93 to 0.99. Preliminary statistics of model and sunphotometer data as well as previous studies indicate that this event, in the Arctic region, must be considered extreme (such AOD was not observed in Svalbard since 2005) with a significant impact on energy budget.

Annual changes of aerosol optical depth and Ångström exponent over Spitsbergen

In this work we present the annual changes of two major, climate related aerosol optical parameters measured at three Spitsbergen locations, Ny-Alesund, Longyearbyen and Hornsund over a period between 2000 and 2012. We discuss the changes of aerosol optical depth (AOD) at 500 nm and the Angstrom exponent (AE) (440–870 nm) measured with use of different types of sun photometers. For the measurement data we adopted several data quality assurance techniques and the calibration of the instruments was taken into consideration. The results obtained show that marine source has been a dominating of aerosol sources over Spitsbergen. Some years (2005, 2006, 2008 and 2011) show very high values of AOD due to strong aerosol events such as the Arctic Haze. In general the mean AOD values increase over the period of 2000 and 2012 over Spitsbergen. This may indicate the presence of larger scale of atmospheric pollution in the region.