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Radiation and Cloud Data
Humidity data are given for insight into cloud conditions. Often, when relative humidity is high, clouds are present.
Cloud amount is estimated here using measured solar radiation and modeled clear-sky solar radiation flux. The difference between simulated 'clear-sky solar radiation flux' and the solar measured radiation flux yields information of how much the sun is obscured by clouds. Over highly reflective surfaces, however, multiple scattering of solar radiation fluxes between clouds and the surface violate, to varying degrees, the assumption that clouds only absorb solar radiation. This cloud estimate is most accurate under the following conditions: A) when thick low 'stratus' clouds are present; B) the sun angle is large (sun angle is largest in summer); and C) when the surface reflectivity is relatively low, i.e. in summer, when surface melting darkens the snow/ice surface. Please use caution with this cloud estimate for aviation purposes, as the uncertainty as to the true cloud amount may be high! No winter cloud estimates are available because this method to estimate cloud amount is based on solar radiation only. For further information about this cloud estimate, read the reference below or e-mail: your questions and comments to the e-mail: link below.
Box, J. E., Polar Day Effective Cloud Opacity in the Arctic Derived from Measured and Modeled Solar Radiation Fluxes, MA Thesis, Department of Geography, University of Colorado, Boulder, CO, Cooperative Institute for Research in Environmental Sciences, 111 pp, 1997.
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Began on October 22, 2001