A. A. Isakov

Optical and microphysical parameters of the aerosol in the smoky atmosphere of the Moscow region in 2010

513 According to the data of ecological monitoring in the city of Moscow and Moscow region, it was found that during the period of the smoky atmosphere in the summer of 2010, the mass concentration of the smoke aerosol with the diameter of particles less than 10 μm (PM10) reached extreme values for Moscow, 1.6– 1.7 mg/m 3 . According to the measurements at the Meteorological Observatory of the Moscow State University (MO MSU) and in the Moscow region at the Zvenigorod Scientific Station of the Oboukhov Institute of Atmospheric Physics, Russian Academy of Sciences (ZSS IAP), based on the data of sun photom� eters CIMEL, which are included in the global moni� toring network in the atmosphere column AERONET, the maximum values of the optical aerosol thickness at a wavelength of 500 nm during the peatbog forest fires exceeded 4.5. Analysis of the spectropolarimetric measurements demonstrated that the optical charac� teristics of the studied smoke in the surface layer have a significant difference from the optical characteristics of the smoke from the forest and peatbog fires in 2002 [1, 2]. The microphysical properties of the smoke in 2002 retrieved from the data of optical characteristic measurements are also notably different from the microphysical characteristics observed previously, including the smoke in 2002 in the Moscow region. In 2010, during the period of the intensive smoky atmo� sphere, the distribution function for the aerosol parti� cles appeared very narrow and the major part of the volume (mass) of the aerosol smoke particles belonged to the submicrometer range. ,

Influence of a solar eclipse on thermal stratification and the turbulence regime

During the total solar eclipse on March 29, 2006 [1], researchers in Kislovodsk measured variations in the flux of the total shortwave radiation, meteorological elements (wind speed and direction and relative air humidity), and turbulence parameters in the surface atmospheric layer, vertical profiles of air temperature in the layer 0‐600 m, functions of particle size distribution (0.20‐1.50 µ m), and concentrations of light ions. It was found that the decrease in the maximum air temperature caused by the eclipse reached 3.5°C in the surface atmospheric layer and approximately 2°C at an altitude of 600 m a.s.l. After the full phase of the eclipse, turbulent kinetic energy decreased by a factor of 2.5, dispersion of the vertical component of the wind speed decreased by a factor of 2.3, turbulent heat flux decreased by a factor of 3.5, and dispersion of turbulent pulsations of air temperature decreased by a factor of 10. Despite the long history of investigations of eclipses [2], the influence of the solar eclipses on processes in the boundary atmospheric layer has not yet been studied sufficiently enough [3‐5]. It is clear that a solar eclipse should lead to variations in the thermal regime of the boundary atmospheric layer, increase in the relative air humidity, and consequent increase in the size of aerosol particles. Variations in the parameters of aerosol along with other factors can change notably the electric characteristics of the surface atmosphere [6]. Decrease in the near-surface air temperature can also lead to variations in the turbulence regime. In order to study the quantitative variations in the above-mentioned parameters of the lower atmosphere during the total solar eclipse in the last decade of March in Kislovodsk (altitude ~900 m a.s.l.), the following measurements were carried out at the urban meteorological station: flux F of total shortwave radiation (CNR1 net radiometer (Kipp and Zonen, Netherlands); accuracy ± 10 W/m 2 ), meteorological parameters (accuracy of measurements: air temperature ± 0.3°C , relative humidity ± 5% , components of wind speed ± 0.15 m/s), turbulent pulsations (digitization step 0.1 s) of three components of wind speed and air temperature using a Meteo-2M acoustic meteorological station (Institute of Atmospheric Optics, Tomsk), vertical profiles of air temperature (time averaging 5 min, spatial averaging 50 m, accuracy of measurements ± 0.5°C ) in layer 0‐ 600 m (MTP-5 UHF microwave profiler of the Central Aerological Observatory [8]), concentrations of negative light ions using a SIGMA-1 counter of aeroions (accuracy of each measurement ± 30% , time constant 1.5 s, mobility of ions >0.4 cm 2 / W · s), and distribution function of the dry base of aerosol particles in the size range 0.20‐1.50 µ m (LAS-P laser spectrometer of aerosols, averaging time of differential countable concentrations of particles 15 s, and random error of measurements of countable concentrations 20%). Calibration of the laser spectrometer was carried out using nuclear filters, which allowed us to increase the accuracy of determination of the boundaries of the particle size ranges determined by the spectrometer.

The influence of solar eclipse on the processes in the atmospheric boundary layer

The effects of an eclipse on the atmospheric boundary layer in Novosibirsk are studied in a period of total solar eclipse on August 1, 2008. Variations caused by the eclipse of the temperature near the ground, vertical temperature profiles in the atmospheric boundary layer, and turbulence parameters are determined. Variations of the total water vapor content and aerosol parameters in the near-ground atmospheric layer during the solar eclipse are analyzed.

On the comparison of the average arrival directions of air masses in the Moscow region versus the average Hanel parameters and average particle refractive indices

In January–July 2008, based on spectropolarimetric measurements, we obtained a time series of diurnally averaged values of the Hanel parameter, the aerosol particle refractive index, and the total aerosol particle volume. It is shown that when the air masses change upon the passage of atmospheric fronts, the latter two quantities vary synchronously and in antiphase. For the entire observation series, we obtained an array of two-day back trajectories for the Zvenigorod Scientific Station (ZSS). We analyzed the relation between the air mass arrival direction and the character of the variations of the Hanel parameter χ and particle refractive index n. It is shown that on average, minimum n values are characteristic of aerosol-rich air masses arriving in the Moscow region from the south, namely, from the Rostov region, the Caucasus, and Turkey. Maximum n values are recorded in maritime Arctic masses arriving from the north and north-northwest, in particular, from the North Atlantic and Barents Sea. Maximum average χ values (≈0.6) were observed in continental masses, having arrived from near-Caspian regions, and minimum values (about 0.35) were observed in Arctic masses. For air masses in all western bearings, the average χ value turned out to be approximately constant at about 0.45. There is no relation between the n and χ variations for both synchronously measured separate values and for average values.

Moscow smoke haze in October 2014. Variations in the aerosol mass concentration

Variations in the aerosol mass concentration in the smoky atmosphere of the Moscow region in autumn 2014 have been analyzed. The soot mass fraction and ratio between the PM2.5 and PM10 mass concentrations were typical of the fires in boreal forests. The smoke event in the Moscow region was due to the long-range transfer of the smoke aerosol, which was confirmed by a joint analysis of aerospace monitoring data and inverse trajectories of air mass transfer, and local fires in the Moscow region. As a result, statistical parameters of variations in the smoke aerosol mass concentrations were atypical, including empirical distribution functions and power spectra.

Long-Period Variations in the Optical and Microphysical Parameters of Surface Aerosol in a Moscow Suburb

The mass concentration M of surface submicron aerosol and its condensation activity χ were measured at the Zvenigorod Scientific Station of the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, in 2001–2006. Variations in these quantities on scales of several days to several months are analyzed. It is shown that the occurrence of dense and superdense hazes over central Russia became more frequent during these years. This resulted in a change in the character of the seasonal dependence of the mass aerosol concentration M: ordered oscillations whose amplitude increases from year to year appeared in the seasonal cycle of M. Due to more frequent cases of dense and superdense hazes in 2002–2006, a significant monotonic increase is observed in the annual means of M. The annual mean of M increased more than twofold in 2005 (56 μm/m3) compared to 2001 (23 μm/m3). The time regimes of M and χ are characterized by variations with periods in the vicinity of 10, 20, and 40–50 days, as well as variations with longer periods within 70–100 days. In addition, the variability of mass concentration is of a strongly intermittent character. A cross-spectral analysis has shown that, on the whole, variations in M are coherent with those in χ. If the parameters M and χ vary on the same time scales, then, as a rule, variations in M lag behind variations in χ by several days. To understand the relationship between the parameters M and χ, special investigations, including studies of aerosol composition, are needed.

On the nature of long-period variations in mass concentration of near-ground aerosol

Variations in the aerosol concentration with periods more than one month are analyzed using measurements of mass concentration of the near-ground aerosol at Zvenigorod Scientific Station of the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences. It is shown that the variations can be associated with the periodic recurrences of atmospheric transport trajectories from certain directions. We considered the cases when long-period variations in aerosol concentration were due to episodes of increased or decreased concentrations caused by aerosol advection from the corresponding directions. In particular, the 1.5-month variations in the aerosol mass concentration in 1995 were found to be due to the 1.5-month recurrences of the concentration maxima caused by southeasterly transport. The three-month periodicity of the transport episodes from directions of Baltic and North Atlantic in 2004 manifested themselves in 3-month recurrence of the aerosol concentration minima. A statistical relation is revealed between the near-ground aerosol concentration and the Arctic upper troposphere dynamics.

Analysis of relationship between condensation activity of surface aerosol and its chemical composition and relative air humidity according to measurements at the Zvenigorod Scientific Station

Data of IR transmission spectra of aerosol samples and measurements of optical characteristics of surface aerosol at the Zvenigorod Scientific Station are used to study the statistical relationship between the Hänel condensation activity parameter and relative air humidity and the basic chemical components of aerosol, namely, sulfate, nitrate, and mineral components, contained in particles with diameters of 1–2 μm. It is found that the Hänel parameter of nitrate-containing surface aerosol decreases with an increase in relative air humidity. An increase in the fraction of nitrates in micron particles is likely to lead to a minor increase in the Hänel parameter. Poorly soluble mineral particles present in the 2-micron fraction of aerosol lead to a decrease in the Hänel parameter. Values of the Hänel parameter, characteristic for sulfate aerosol, are likely to be in the range of 0.4–0.6. Seasonal variations in the Hänel parameter are caused by changes in the aerosol chemical composition, to some degree.

Siberian Smoke Haze over European Territory of Russia in July 2016: Atmospheric Pollution and Radiative Effects

We have characterized the large-scale smoke pollution of the European territory of Russia (ETR) and adjoining areas in July 2017, caused by long-range transport from forest-fire areas in Siberia, confirmed by calculations of ten-day back trajectories of air mass motion to the ETR urban area, spanning Archangelsk to Rostov-on-Don. The smoke-laden ETR area with an AOD > 0.3 (average value being 0.43 and maximal value being 2.5) on July 25, 2016, covered 5 million km2, and the total smoke mass was ~1.2 million tons. It is shown that the daily average mass concentration of aerosol with particle sizes less than 2.5 μm exceeded the corresponding maximum permissible concentration in the Moscow region during the period from July 24 to 27, 2016. The influence of local sources on aerosol and gas pollution of atmospheric air was estimated. The smoke haze in 2016 was found to be deficient in carbon monoxide as compared to smoke pollution in 2010. It is shown that the thermal and wind stratification in the atmospheric boundary layer markedly influenced the pollution level in the smoke-laden urban atmosphere. Smoke aerosol radiative effect was estimated. The average aerosol radiative forcings at the top and bottom of the atmosphere over ETR on July 25, 2016, were–29 and–53 W/m2, and extreme forcings reached–112 and–215 W/m2, respectively.

Relationship between aerosol parameters and air masses in central Russia

According to results of long-term measurements in the Moscow region, relationships between parameters of the near-surface aerosol and directions of air masses arrival were analyzed. The results for 2004, 2006, 2007, 2010, and 2011 were taken into consideration. The data were obtained with a spectropolarimeter. Three-day back trajectories were calculated using a standard NOAA HYSPLIT program. All possible directions of arrival of air masses were divided into eight sectors. A trajectory belonging to a certain sector was defined by its initial point and trajectory shape. The basic characteristics of aerosol, mass concentration M and the Hanel parameter, were averaged over a sector. A narrow maximum in the Baltic region and North Atlantic sectors were identified in the frequency distribution of trajectories. The mass concentration maximum falls in the Ukraine-Mediterranean sector. Average values of the Hanel parameter do not depend on the direction of air mass arrival to the observational site. The averaged time distribution of trajectories distinctly shows periodic peaks with a period of about 11–12 weeks for Baltic region-Russian Atlantic and Western Arctic-Polar Urals sectors. In other sectors, their time distributions are relatively uniform.