Characterization of the radiative properties of inhomogeneous clouds

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

OSTI ID:83205

Stephens, G L; Gabriel, P M; Evans, K F; Stackhouse, P ^[1]

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1. Colorado State Univ., Ft. Collins, CO (United States)

One of the major sources of uncertainty in climate-based studies is related to clouds and their influence on the radiative transfer. Two broad issues are of relevance to this problem: (1) the influence of clouds on broadband radiative transfer and thus on cloud energetics and (2) the influence of clouds on spectral transfer and thus on remote sensing applications. The work described addresses key aspects of both these issues. One of the key issues in parameterizing cloud radiative processes is to account for the sub-grid scale variability. A common approach for incorporating horizontal cloud inhomogeneity in radiative transfer calculations is the use of cloud fraction. We have attempted to determine the limitations of this approach by performing radiative transfer calculations applied to inhomogeneous clouds embedded in two dimensions. For solar radiation, use of cloud fraction leads to non-unique domain averaged albedos; exhibiting significant variations. We have developed new approximate methods to account for the sub-grid scale variability of clouds on the radiative transfer. This approximate method is based on a first order closure technique. Exploiting the translational invariance of the equation of transfer leads to a one-dimensional, plane-parallel-like equation with a modified source term. This approach results in computational speeds exceeding that of the independent pixel approximation and improved accuracy over the latter as determined by numerical solutions of the two-dimensional transfer equation.

• Research Organization: USDOE Office of Energy Research, Washington, DC (United States). Environmental Sciences Div.
• OSTI ID: 83205
• Report Number(s): CONF-940277--; ON: DE95009951
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ACCURACY
CALCULATION METHODS
CLOUDS
OPTICAL PROPERTIES
PARAMETRIC ANALYSIS
RADIANT HEAT TRANSFER
REMOTE SENSING
SOLAR RADIATION