Comparison of surface radiative flux parameterizations - Part II. Shortwave radiation

This paper presents a comparison of several shortwave (SW) downwelling radi ative flux parameterizations with hourly averaged pointwise surface radiati on observations made at Jokioinen and Sodankyla, Finland, in 1997. Both cle ar and cloudy conditions are considered. The clear-sky comparisons included six simple SW parameterizations, which u se screen level input data, and three radiation schemes from numerical weat her prediction (NWP) models: the former European Centre for Medium-Range We ather Forecast (ECMWF) scheme, the Deutscher Wetterdienst (DWD) scheme, and the High Resolution Limited Area Model (HIRLAM) scheme. Atmospheric-soundi ng profiles were used as input for the NWP schemes. For the cases with clou ds, three simple cloud correction methods (mainly dependent on the total cl oud cover) were tested. In the SW clear-sky comparisons, the relatively simple scheme by Iqbal prov ided the best results, surprisingly outperforming even the NWP radiation mo dels. Simple cloud corrections performed poorly in the SW region. Out of th ese schemes, a new cloud correction method developed using the present data provided the best results. (C) 2001 Elsevier Science B.V. All rights reser ved.