Sinks, inflows, and the state of aerosol in the lower atmosphere of the Far Moscow region during winter months

Abstract

According to observations during the winters of 2005–2007 in the central part of the European territory of Russia (ETR), the influxes, sinks, and the state of the atmospheric aerosol with a diameter D = 3–100 nm were determined primarily by the mixing conditions in the lower troposphere and the prehistory of the air masses. In contrast to the well-studied emissions of new aerosols (ENA) in the boreal forests of Northern Europe, in the mixed forests of the Central ETR, intense ENAs were observed not only in anticyclones but also in cyclones, as well during the change of atmospheric fronts. The time interval from the onset of the ENA to the time that the particle inflow reached a maximum was tens of minutes, whereas Northern Europe was characterized by time spans on the order of a few hours. The aerosol emissions were found to be less significantly related to the wind speed and direction, as well as with the state of the underlying surface. The occurrences of regular ENAs coincided with the onsets of the morning breakdown of nighttime near- ground inversions. The ENA stopped after the upper boundary of the inversion layer reached the 150- to 200-m level. In 50–60% of the episodes, the number N, area density S, and mass M concentrations of new particles reached N = (3–5) × 105 1/cm3, S = 200–330 μm2/cm3, and M = 50 μg/m3, a factor of 50–500 larger than the nighttime minima and a few orders of magnitude larger than the background values. Sinks of the aerosol particles to the underlying surface took place from the time of the formation of the evening inversions up to the beginning of the morning breakdown of the layer. For the analysis, we used the data of the electric spectrometers of aerosols with D = 3–1000 nm, data of acoustic sensing, and the vertical transects of the temperature and wind speed and direction at the atmospheric depth of 4–300 m measured during meteorological tower observations in Obninsk.