The Cryosphere Discussions www.the-cryosphere-discuss.net 1994-0432 1994-0440 2 4 2008 10.5194/tcd-2-487-2008 http://www.the-cryosphere-discuss.net/2/487/2008/ http://www.the-cryosphere-discuss.net/2/487/2008/tcd-2-487-2008.html http://www.the-cryosphere-discuss.net/2/487/2008/tcd-2-487-2008.pdf 487 511 2008-07-01 On the use of incoming longwave radiation parameterizations in a glacier environment J. Sedlar josephs@misu.su.se R. Hock Department of Meteorology, Stockholm University, Sweden Geophysical Institute, University of Alaska Fairbanks, USA Department of Earth Sciences, Uppsala University, Sweden Energy balance based glacier melt models require accurate estimates of incoming longwave radiation since it is generally the largest source of energy input. Multi-year near-surface meteorological data from Storglaciären, northern Sweden, were used to evaluate commonly used longwave radiation parameterizations in a glacier environment under clear-sky, overcast-sky and all-sky conditions. The tested parameterization depending solely on air temperature performed worse than those including also air humidity. Adopting parameter values from the literature instead of fitting them to the data resulted in similar correlation coefficients between modeled and measured radiation, but generated larger biases, emphasizing the need to derive site-specific coefficients. Nearly all models including those fitted to the data tended to overestimate longwave radiation during periods of low longwave radiation, and vice versa when radiation input was high. An attempt was made to parameterize cloud cover using top of atmosphere and measured global radiation. Both hourly and daily calculations of incoming longwave radiation using the cloud parameterization provided similar, or even stronger, correlations to the measurements compared to using observed cloud fraction as input. 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