Solar Radiation Climatology of Alaska |
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| Authors: | D Dissing G Wendler |
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| Institution: | (1) Alaska Climate Center, Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, U.S.A., US |
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| Abstract: | Summary There are only six locations in Alaska for which global radiation data of more than a year in duration are available. This
is an extremely sparse coverage for a state which covers 1.5×10&6 km2 and stretches over at least three climatic zones. Cloud observations are, however, available from 18 stations. We used fractional
cloud cover and cloud type data to model the global radiation and thus obtain a more complete radiation coverage for Alaska.
This extended data set allowed an analysis of geographic and seasonal trends.
A simple 1-layer model based on Haurwitz’s semi-empirical approach, allowing for changes in cloud type and fractional coverage,
was developed. The model predicts the annual global radiation fluxes to within 2–11% of the observed values. Estimated monthly
mean values gave an average accuracy within about 6% of the measurements. The estimates agree well with the observations during
the first four months of the year but less so for the last four. Changing surface albedo might explain this deviation.
Previously, the 1993 National Solar Radiation Data Base (NSRDB) from the National Renewable Energy Laboratory (NREL) modeled
global radiation data for 16 Alaskan stations. Although more complete and complex, the NREL model requires a larger number
of input parameters, which are not available for Alaska. Hence, we believe that our model, which is based on cloud-radiation
relationship and is specifically tuned to Alaskan conditions, produces better results for this region. Annual global solar
radiation flux measurements are compared with results from global coverage models based on the International Satellite Cloud
Climatology Project (ISCCP) data. Contour plots of seasonal and mean annual spatial distribution of global radiation for Alaska
are presented and discussed in the context of their climatic and geographic settings.
Received July 16, 1997 Revised May 18,1998 |
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