Modal structure of the atmospheric aerosol particle size spectrum for nucleation burst days in Estonia

The modal structure of an atmospheric aerosol size spectrum determines to a significant extent the role of aerosol particles in the formation of weather and climate and their potential danger to living beings. In this paper, the modal structure of the atmospheric aerosol particle size spectra for nucleation burst days was investigated using data acquired at a rural measurement site in Estonia during the year 2005. The measurements were made with the original electrical aerosol spectrometer designed at the Institute of Environmental Physics of the University of Tartu. The performed analysis relied on air mass histories, factor analysis and least-square fitting. The highest particle number concentrations were found in Arctic air masses. The start time of a nucleation burst was found to be dependent on the air mass type: in Arctic air masses nucleation occurred before the noon, whereas in the polar air it occurred in the afternoon.