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Estimating Solar Radiation under Variable Cloud Conditions

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Measurement of solar radiation is not often feasible except at instrumented research facilities. Although estimates of direct beam solar radiation in the absence of an atmosphere or with cloudless skies may be obtained from theoretical equations or tables, they are unrealistic to the extent that they fail to consider scattered solar radiation and are unapplicable whenever clouds are present. This paper presents a simple model for estimating daily total solar radiation by modifying existing theoretical equations to take into account scattered radiation from clear skies and reflected and transmitted radiation from clouds. Observational data required are: station latitude, slope direction and inclination, and estimated mean hourly cloud cover, by month. Tests of estimated daily total solar radiation by months against comparable measured radiation for several areas in the Pacific Northwest indicate that the model yields estimates that reproduce measured daily totals with a high degree of accuracy. Results were similar when the model was used to estimate solar radiation in the northeastern United States. Forest Sci. 24:363-373.

Keywords: Cloud cover; model testing

Document Type: Journal Article

Affiliations: Forestry Sciences Laboratory, Pacific Northwest Forest and Range Experiment Station, Corvallis, Oregon 97331

Publication date: 1978-09-01

More about this publication?
  • Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
    Forest Science is published bimonthly in February, April, June, August, October, and December.

    2015 Impact Factor: 1.702
    Ranking: 16 of 66 in forestry

    Also published by SAF:
    Journal of Forestry
    Other SAF Publications
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