Fractionation of Ground-Level Aerosol from IR Radiation of the Snow Surface: Observations in Tomsk Oblast

This article analyzes the results of measurements of the aerosol count concentration in the surface air in the range from 0.3 to 20.0 μm in 15 intervals. The measurements are carried out using a Grimm 1.108 aerosol spectrometer installed at the Fonovaya Observatory (Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk (IAO SB RAS, Tomsk). The calculation of the statistical parameters of the distribution of surface aerosol fractions was carried out using a sample compiled on the basis of a continuous series of measurements from November 17, 2022, to January 30, 2023. The sample size is 1799 hourly observations. A service program was written to work with the sample, as well as to visualize the calculations. The features of the effect of photophoretic forces on the average diurnal dynamics of the fractional distribution of aerosol particles in the surface layer are assessed in conjunction with the analysis of reverse trajectories of transport of moisture-bearing air masses and taking into account the time intervals of snow accumulation at the Fonovaya observatory in the first half of winter 2022/2023. A certain relationship is established between the increase in the number concentration of particles in the range of 0.3–2.0 μm and the effect of photophoretic forces in different phases of snow cover growth associated with the fall of stratigraphically significant snowfalls. It is postulated and proven that the cause of this phenomenon is the levitation of particles in the field of infrared radiation leaving the surface of the snow, caused by the action of snow photophoresis. Obviously, this circumstance should be taken into account when constructing transport models of the vertical transport of aerosols in the lower troposphere. In addition, during breaks between snowfalls and during anticyclonic weather conditions, snow photophoresis can be considered a potentially significant mechanism for the increasing concentration of pollutants on the snow surface and in the ground air.