Model estimates of short-wave solar radiation fluxes for summer conditions in the southern part of Western Siberia in the presence of single-layer of the low and high-level clouds are presented. The cloudiness characteristics were obtained on the basis of statistical models based on long-term satellite MODIS observations: the ranges of variability of the optical thickness and effective particle radius were 1.5-40 and 7.5-25 mkm for liquid clouds and 1-5 and 15-50 mkm for ice clouds, respectively. These low-level clouds characteristics variations lead to changes in the average daily radiation fluxes in the range of 150-300 W/m2 at the bottom (BOA) and 130-230 W/m2 at the top (TOA) of the atmosphere and for ice clouds 230-310 W/m2 at the BOA and 140-220 W/m2 at the TOA. At a fixed optical depth, there is a relatively weak dependence of the average daily radiation fluxes on the effective particle radius.
Calculations of reflected solar radiation in crystal clouds composed of horizontally oriented plates or Parry columns are presented. The radiation intensity was simulated for a limited set of observation and illumination conditions using the optical characteristics of clouds calculated by the geometric optics method for particles with shape parameters 0.1 (plates) and 2.5 (Parry columns).
We present the first results of our numerical study aimed at identifying the possible effects of the atmospheric evolution of biomass burning (BB) aerosol on the aerosol direct radiative forcing (DRF). We used a microphysical box model, which implements different parameterizations of the organic aerosol evolution within the volatility basis set framework, along with the Mie theory and radiative transfer calculations to simulate the dynamics of the physical, optical and radiative properties of polydisperse carbonaceous aerosol in an isolated BB smoke plume. We found that atmospheric transformations of the organic fraction of BB aerosol can result in major changes in the BB aerosol DRF. These changes are related to the underlying variations in the aerosol optical depth and single scattering albedo in a nonlinear manner and are especially strong in optically dense plumes.
The article presents the data bank of light scattering matrices for ice hexagonal particles with a preferentially horizontal spatial orientation. The calculations were performed within the geometric optics approximation for flutter angles from 0 to 180 degrees in increments of 1 degree. It is shown that the light scattering matrix for randomly oriented ice crystals of cirrus clouds is fundamentally different from the light scattering matrix for particles with a preferentially horizontal spatial orientation. This fact can play a significant role in solving the radiation transfer problem through cirrus clouds and have to be taken into account in climate modeling.
We present a statistical algorithm for calculating the mean intensity of reflected solar radiation in limb sensing geometry taking into account the effects of the stochastic geometry of liquid-water clouds. It is shown that the 3D cloud effects determine the main regularities of the formation of solar radiation brightness fields when changing a perigee height from the level of the underlying surface to the cloud top. A comparison of the intensities in the clear sky, overcast and broken clouds for different perigee heights and illumination conditions is carried out (visible range).
The paper presents an original statistical algorithm for calculating the mean intensity of solar radiation in broken clouds I , taking into account the sphericity of the atmosphere. The algorithm is based on numerical averaging of the radiative transfer equation and introduction of an additional randomness (randomization). We discuss the results of numerical experiments, carried out to estimate the effect of statistics (numbers of cloud realizations and photon trajectories in a single realization) on the accuracy of the I calculations and laboriousness of the algorithm under different observation and illumination conditions.
We present original statistical algorithms for calculating brightness fields of upward and downward solar radiation in deterministic inhomogeneous clouds in the plane-parallel and spherical atmospheric models. Poisson model on the basis of point fluxes in space is used to simulate the cloud fields. We implemented a few modifications of the algorithms, differing in the methods for simulating free path length and accounting for the molecular absorption. Results of crosschecks of the developed modifications and estimations of their efficiency are presented.
Occupied a vast area, Siberia is marked by diverse climate and pronounced seasonal cycle. For regional and global climate models it is important to account for seasonal features of atmospheric aerosol. The paper briefly describes an algorithm “Sun-Sky Measurements for Aerosol ReTrieval” (SSMART, Version 1.1) for recovering aerosol optical (single scattering albedo, asymmetry factor of scattering phase function) and microphysical (particle size distribution, complex refractive index) characteristics. The aerosol properties retrieved using the SSMART algorithm from measurements of the spectral extinction and almucantar sky radiance carried out at Tomsk AERONET station in winter are presented. The results of comparison with the data presented on the AERONET website at Level 1.5 are discussed. Both individual and averaged over an extended set of atmospheric situations solutions of the inverse problem are analyzed. The seasonal (summer and winter) variability of aerosol properties is studied.
We consider the algorithm and results of numerical simulation of irradiance at the Earth’s surface E in the spectral range of 0.4-0.7 μm in the aerosol-molecular atmosphere and in the presence of isolated cloud. We analyze the differences in the irradiance E in the clear-sky and little cloudy atmosphere in dependence of optical and geometrical parameters of cloud, its position relative to the receiver and the illumination conditions.
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