Mean fluxes of visible solar radiation in broken clouds

Conference · Sat Apr 01 04:00:00 EST 1995

OSTI ID:83219

Zuev, V E; Titov, G A; Zhuravleva, T B; Popov, S Y ^[1]

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1. Institute of Atmospheric Optics, Tomsk (Russian Federation)

Generally, radiation codes for general circulation models (GCMs) include, together with other procedures, calculations of vertical profiles of upward and downward radiation fluxes which are needed to calculate radiant heat influxes. These last radiative characteristics serve as an input for a number of atmospheric processes predicted from GCMs, e.g., the equation of radiant heat influxes is sometimes a starting point for modeling the formation and evolution of cloud fields; the equation of heat balance of the earth`s surface involves solar and thermal radiation fluxes that govern the surface thermal regime; and so forth. The question of the accuracy of determinations of the upward and downward radiation fluxes at different atmospheric levels is important. Most of the present GCM codes make use of the models of plane-parallel, horizontally homogeneous atmosphere and are based computationally on solving the equation of radiative transfer using deterministic optical characteristics. In the presence of clouds partially covering the sky, flux values represent a linear combination of clear- and overcast-sky fluxes weighted by a specific value of cloud fraction. Such an approach is adequate for the stratus-clouds-only cases, when the parameter {gamma} {approx} 0 (with {gamma} = H/D, H the cloud layer thickness, and D the mean horizontal cloud size). Under the cumulus cloud conditions (y {approx} 1), the approach can be regarded merely as a first, fairly crude approximation, recognizing that the shortwave radiative transfer is affected remarkably by the stochastic geometry of cloud fields. Mean albedo and transmission of shortwave radiation in the system {open_quotes}clouds-aerosol-underlying surface{close_quotes} are sufficiently investigated. In the present work, we raise the question about the value of the effect the cloud field random geometry has on the mean upward and downward fluxes of the visible and near-IR solar radiation throughout the atmosphere.

• Research Organization: USDOE Office of Energy Research, Washington, DC (United States). Environmental Sciences Div.
• OSTI ID: 83219
• Report Number(s): CONF-940277--; ON: DE95009951
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ABSORPTION
CALCULATION METHODS
CLOUDS
GENERAL CIRCULATION MODELS
GEOMETRY
NEAR INFRARED RADIATION
RADIANT HEAT TRANSFER
SOLAR RADIATION
THERMAL RADIATION