Smoke aerosol and its radiative effects during extreme fire event over Central Russia in summer 2010

Different microphysical, optical and radiative properties of aerosol were analyzed during the severe fires in summer 2010 over Central Russia using ground measurements at two AERONET sites in Moscow (Meteorological Observatory of Moscow State University – MSU MO) and Zvenigorod (Moscow Region) and radiative measurements at the MSU MO. Volume aerosol size distribution in smoke conditions had a bimodal character with the significant prevalence of fine mode particles, for which effective radius was shifted to higher values (<i>r</i><aub>eff-fine</aub> = 0.24 μm against approximately 0.15 μm in typical conditions). For smoke aerosol, the imaginary part of refractive index (REFI) in the visible spectral region was lower than that for typical aerosol (REFI<sub>λ =675 nm</sub> = 0.006 against REFI<sub>λ =675 nm</sub> = 0.01), while single scattering albedo (SSA) was significantly higher (SSA<sub>λ =675 nm</sub> = 0.95 against SSA<sub>λ =675 nm</sub> ~ 0.9). Extremely high aerosol optical thickness at 500 nm (AOT500) was observed on 6–8 August reaching the absolute maximum on 7 August in Moscow (AOT500 = 6.4) and at Zvenigorod (AOT500 = 5.9). A dramatic attenuation of solar irradiance at ground was also recorded. Maximum irradiance loss had reached 64% for global shortwave irradiance, 91% for UV radiation 300–380 nm, and 97% for erythemally-weighted UV irradiance at relatively high solar elevation 47°. Significant spectral dependence in attenuation of solar irradiance in smoky conditions was mainly explained by higher AOT and smaller SSA in UV (0.8–0.9) compared with SSA in the visible region of spectrum. The assessments of radiative forcing effect (RFE) at the TOA indicated a significant cooling of the smoky atmosphere. Instant RFE reached −167 Wm<sup>−2</sup> at AOT500 = 6.4, climatological RFE calculated with August 2010 monthly mean AOT was about −65 Wm<sup>−2</sup>, compared with −20 Wm<sup>−2</sup> for typical aerosol according to the 10 yr period of measurements in Moscow

Unstady heat-mass-transfer and fuel distributions in flows downstream the gas-dynamic flame holder

A model of non-stationary heat and mass transfer of fuel droplets with a swirling air flow is developed. The model includes the definition of the air flow structure, identification of configurations of liquid jets flowing into the air flow, the calculation of characteristics of their breakup taking into account the processes of drop breaking and coalescence, the calculation of droplet and fuel vapor concentration distribution in the work volume. The study was performed as applied to a combustion chamber with a front gas-dynamic flame holder. The optimal combination of major gas-dynamic parameters that determine the mode of operation of the device in question the value of the air flow swirl and the intensity of the air traverse feed through the flame holder is determined. The flow structure and the distribution of liquid-droplet and vaporous fuel concentrations downstream the flame holder are specified for this combination. The calculation results are compared with the experimental data

Characteristics of a fuel spray downstream the pressure atomizers under high pressure in the combustion chamber

The paper presents numerical calculations of a fuel spray downstream a swirl-type fuel injector carried out for various pressures in the combustion chamber using the model of liquid film motion. The effect of the chamber pressure, or, to be more exact, the air density in the pressure chamber on the fuel spray characteristics is investigated. The mathematical model was constructed on the assumption of one- dimensional and steady swirling flow. The liquid is considered to be incompressible and have zero pressure gradient in the direction of the film motion and in the tangential direction. The influence of viscous forces on the motion of liquid is neglected, but the viscous interaction at the interface between liquid and gas is taken into account. The change of velocity in the circumferential and normal directions can be neglected, because in practice the film thickness is considerably smaller than the spray radius. It is shown that the pressure increase in the combustion chamber makes spray characteristics significantly different from those observed at atmospheric pressure. An increase of pressure results in increasing the thickness of the fuel film and decreasing the spray-cone angle. It leads to an increase in the average Sauter diameter in the spray of fuel atomized by the pressure atomizer. The air flow downstream the swirl nozzle has the opposite influence on the size of drops in case of increased pressure in the chamber

Comparative analysis of fuel distribution downstream of the gas-dynamic flame holder with various methods of injection

The article deals with the problems of atomization and distribution of liquid fuel in a swirling flow downstream of the front-end gas-dynamic stabilizer designed for the use in gas turbine engine combustion chambers. The task is to compare the distributions of droplet-liquid fuel in the wake of the stabilizer when the fuel is injected from the side and end surfaces of the device in question. It is shown that the calculations performed according to a stationary model are qualitatively different from the non-stationary ones in both fuel supply options. However, in the first approximation, the distributions of liquid droplet fuel fed from the side and end surfaces of the stabilizer are similar. An experimental study of the spray characteristics was conducted by the Shadowgraphy method of diagnosing droplet-air fluxes with the fuel supplied at an azimuthal angle of 45 from the side surface of the gas-dynamic stabilizer. It is shown that if the fuel is injected at an angle it leads to a change in the velocity distribution in the wake of the stabilizer, and the flow swirl opposite to direction of azimuth fuel supply expands the spray pattern

Assessments of urban aerosol pollution in Moscow and its radiative effects

Simultaneous measurements by the collocated AERONET CIMEL sun/sky photometers at the Moscow State University Meteorological Observatory (MSU MO) and at the Zvenigorod Scientific Station (ZSS) of the A. M. Obukhov Institute of Atmospheric Physics during September 2006���April 2009 provide the estimates of the effects of urban pollution on various aerosol properties in different seasons. The average difference in aerosol optical thickness between MO MSU and ZSS, which can characterize the effect of aerosol pollution, has been estimated to be about <i>d</i>AOT = 0.02 in visible spectral region. The most pronounced difference is observed in winter conditions when relative AOT difference can reach 26%. The high correlation of the AOT's, the Angstrom exponent values and the effective radii between the sites confirms that natural processes are the dominating factor in the changes of the aerosol properties even over the Moscow megacity area. The existence of positive correlation between <i>d</i>AOT and difference in water vapor content explains many cases with large <i>d</i>AOT between the sites by the time lag in the airmass advection. However, after excluding the difference due to this factor, AOT in Moscow remains higher even in a larger number of cases (more than 75%) with the same mean <i>d</i>AOT = 0.02. Due to the negative average difference in aerosol radiative forcing at the TOA of about <i>d</i>ARF<sub>TOA</sub> = −0.9 W m<sup>−2</sup>, the aerosol urban pollution provides a distinct cooling effect of the atmosphere. The PAR and UV irradiance reaching the ground is only 2–3% lower in Moscow due to the pollution effects, though in some situations the attenuation can reach 13% in visible and more than 20% in UV spectral region

EXPERIMENTAL STUDY OF ATOM FLUORESCENCE LINES IN THE LASER PRODUCED PLASMA

Author Institution: Lebedev Physical Institute; Pacific: Oceanological Institute, Russian Academy of SciencesEmission line shapes of laser plasma generated on the surface of an aluminium are studdied experimentally, The shifts of the centers of self-reversed absorption lines with the wave Length 3962 A and 3944 A are registered. Two physical mechanisms of these shifts are discussed