Eurasian Large-Scale Hazes in Summer 2016

Izvestiya, Atmospheric and Oceanic Physics - The technique for constructing the spatial distribution of maximum aerosol optical depth (MAOD) has been used to estimate the optically dense haze...     

Radiative and Thermal Impacts of Smoke Aerosol Longwave Absorption during Fires in the Moscow Region in Summer 2010

The aerosol longwave radiative forcing of the atmosphere and heating rate of the near-surface aerosol layer are estimated for the extreme smoke conditions in the Moscow region in summer 2010. Thermal radiation fluxes in the atmosphere are determined using the integral transmission function and semiempirical aerosol model developed on the basis of standard aerosol models and measurements at the Zvenigorod Scientific Station, Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences. The aerosol radiative forcing reached 33 W/m² at the lower atmospheric boundary and ranged between–1.0 and 1.0 W/m² at the upper atmospheric boundary. The heating rate of the 10-m atmospheric layer near surface was up to 0.2 K/h during the maximum smoke conditions on August 7–9. The sensitivity of the aerosol longwave radiative forcing to the changes in the aerosol absorption coefficient and aerosol optical thickness are estimated.     

The effect that coarse particles have on estimates of both optical and radiation characteristics of dust aerosol

Based on mathematical simulation, quantitative estimates of the effect that coarse dust particles have on the accuracy of retrieving the optical characteristics of aerosol have been obtained from the results of ground-based measurements of the spectral fluxes of both direct and scattered solar radiations. The results of verifying a retrieval algorithm (used at the AERONET ground-based network) based on special test models showed that the aerosol characteristics retrieved with this algorithm are unsuitable for calculating integral solar fluxes and for simulating space spectrometric IR measurements when the concentration of dust particles in the atmosphere exceeds their concentration in the well-known CONT model of continental aerosol by a factor of two or more.     

The radiative and thermal effects of smoke aerosol over the region of Moscow during the summer fires of 2010

The shortwave radiative forcings of smoke aerosol in the cloudless atmosphere during the summer fires of 2010 in European Russia were quantitatively estimated for the land surface and the atmospheric upper boundary from measurement data obtained at the Zvenigorod Scientific Station of the Obukhov Institute of Atmospheric Physics (OIAP ZSS), Russian Academy of Sciences. Variations in the temperature of the surface air layer due to the smoke-induced attenuation of incoming solar radiation were estimated. The most intensive smoke generation in the atmosphere was observed on August 7–9, 2010, when the maximum aerosol optical thickness amounted to more than 4.0 at a wavelength of 550 nm. In this case, the albedo of single aerosol scattering amounted to ∼0.95–0.96 and the asymmetry factor amounted to ∼0.69–0.70. The maximum shortwave radiative forcing of aerosol amounted to about −360 W/m² for the land surface and almost −150 W/m² for the atmospheric upper boundary. During the period of intensive smoke generation, the cooling of the atmospheric surface layer over daylight hours (12 h) amounted, on average, to ∼6°C. The power character of the dependence of the shortwave radiative forcing of aerosol for the land surface on aerosol optical thickness up to its values exceeding 4.0, which was revealed earlier on the basis of data on aerosol optical thickness (up to 1.5) obtained at the OIAP ZSS during the summer forest and peatbog fires of 2002 in the region of Moscow, was supported.     

Modeling radiative forcing by background aerosol on the basis of measurement data

The solar radiation flux incident on the land surface and aerosol radiative forcing are calculated from measurements carried out under clear skies during the summers of 2004 and 2005 at the Zvenigorod Scientific Station (ZSS) of the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences. In these calculations, the following five models of aerosol optical parameters are used: a standard model of continental aerosol, a semiempirical model based on measurement data, and three models obtained from calculations on the basis of the Mie scattering theory for the mean size distribution of aerosol particles (which is retrieved from aureole measurements). A study of the sensitivity of the flux and forcing to the choice of aerosol model has shown that the relative error related to the model choice is not large (<5%) for the incident radiation flux and reaches 120% for aerosol forcing at the atmospheric upper boundary. The aerosol radiative forcing at the atmospheric upper boundary is also estimated and, according to our calculations, varies from −15 to −2 W/m². The use (in calculations) of the values of the albedo of single-scattering and the factor of scattering-indicatrix asymmetry at a wavelength of 550 nm, which were obtained for each of the observation periods, has made it possible to significantly refine the value of aerosol radiative forcing (compared to that calculated for the means of these parameters over all the periods). An even more accurate determination of aerosol radiative forcing is possible only when data on the size-distribution of aerosol particles and their chemical composition for a certain situation under analysis are available. As a result of this study, two models of the optical parameters of background aerosol have been proposed for use in radiation calculations: a semiempirical model and a mean model obtained from the calculations based on the theory of scattering. Both models use the values of the albedo of single scattering and the factor of asymmetry (at a wavelength of 550 nm) retrieved from the measurements for each of the observation periods.     

Large-Scale Haze over Eurasia in July 2016

Doklady Earth Sciences - This paper reports the estimated scales of optically dense haze over Eurasia for the period from July 15 to July 31, 2016, including the Siberian smoky haze (with a smoke...     

Brown Carbon and Black Carbon in the Smoky Atmosphere during Boreal Forest Fires

We have investigated the variability of smoke aerosol absorbing ability with variations in the content of brown carbon (BrC) and black carbon (BC). Using monitoring data on radiative characteristics of smoke aerosol at AERONET stations and the spatial distribution of aerosol optical depth (AOD) obtained by the MODIS spectrometer (Terra satellite), we have detected large-scale smokes during boreal forest fires in Russia and Canada (1995–2012). The spatial distribution (50°–70° N, 95°–125° W) and temporal variability (at AERONET station Fort McMurray) of AOD during the smoking of a part of Canada in July 2012 have been analyzed. AOD probability distributions for July 14–18, 2012, and an estimate of aerosol radiative forcing of smoke aerosol at the upper boundary of the atmosphere have been obtained. We have proposed a technique for the diagnostics of BrC and BC in smoke aerosol particles from the spectral dependence of the imaginary part of the refractive index. At a wavelength of 440 nm, the contributions of BrC and BC to the smokeaerosol absorbing abitity can be comparable in magnitude. In many cases, the absorption spectra of smoke aerosol can be adequately approximated by either power or exponential functions. The presence of BrC in smoke-aerosol particles highly extends the variety of observed absorption spectra in a smoky atmosphere and spectral dependences of single scattering albedo. In the spectral range of 440–1020 nm, the radiative characteristics of smoke aerosol are largely contributed by its fine mode.     

Large-Scale Smoke Haze over the European Part of Russia and Belorus in July 2016

Izvestiya, Atmospheric and Oceanic Physics - The smoke haze over the European part of Russia (EPR) and Belorus in July 2016 has been studied with the use of aerosol optical thickness (AOT) data...