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

This paper presents a comparison of several shortwave (SW) downwelling radiative flux parameterizations with hourly averaged pointwise surface radiation observations made at Jokioinen and Sodankylن, Finland, in 1997. Both clear and cloudy conditions are considered. ear-sky comparisons included six simple SW parameterizations, which use screen level input data, and three radiation schemes from numerical weather prediction (NWP) models: the former European Centre for Medium-Range Weather Forecast (ECMWF) scheme, the Deutscher Wetterdienst (DWD) scheme, and the High Resolution Limited Area Model (HIRLAM) scheme. Atmospheric-sounding profiles were used as input for the NWP schemes. For the cases with clouds, three simple cloud correction methods (mainly dependent on the total cloud cover) were tested. SW clear-sky comparisons, the relatively simple scheme by Iqbal provided the best results, surprisingly outperforming even the NWP radiation models. Simple cloud corrections performed poorly in the SW region. Out of these schemes, a new cloud correction method developed using the present data provided the best results.