Long-term trends in the mass concentration of near-surface aerosol at Zvenigorod Scientific Station of the A. M. Obukhov Institute of Atmospheric Physics RAS from 1991-2019 measurements

Abstract

Estimates of seasonally dependent trends in the mass concentration of the near-surface aerosol are presented on the base of results of 29-year measurements at the Zvenigorod Scientific Station of the A. M. Obukhov Institute of atmospheric physics. The station is located in the woody countryside, 50 km west to Moscow. The multiple regression method is used for the analysis, in which autocorrelation of measurement data on large time scales is taken into account. Two periods are considered: 1991-2002 and 2013-2019. Excluded is the period 2003-2012 when abnormally high aerosol concentrations of unknown origin were often observed. For the periods 1991-2002 and 2013-2018, statistically significant negative trends were obtained for spring and summer seasons, respectively, and for the entire year. The spring trend in logarithm of concentration in 1991-2002 was -2.6% per year, and the annual trend was about -0.7% per year. For 2013-2019 a strong negative trend of about -6% per year was obtained in the summer season, and the annual trend estimate was -2.3% per year. The probable cause of the negative aerosol trend in the spring seasons of 1991-2002 is long-term changes in atmospheric transport. The negative trend in the summer seasons of 2013-2019 is probably due to the negative trend of summer temperature, drying and felling of spruce forest.