Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 3 2007 10.5194/acpd-7-7235-2007 http://www.atmos-chem-phys-discuss.net/7/7235/2007/ http://www.atmos-chem-phys-discuss.net/7/7235/2007/acpd-7-7235-2007.html http://www.atmos-chem-phys-discuss.net/7/7235/2007/acpd-7-7235-2007.pdf 7235 7275 2007-05-30 Two adaptive radiative transfer schemes for numerical weather prediction models V. Venema victor.venema@uni-bonn.de A. Schomburg F. Ament C. Simmer Meteorologisches Institut, Universität Bonn, Auf dem Hügel 20, 53121 Bonn, Germany Meteo Schweiz, Numerical Models, Kraehbuehlstrasse 58, 8044 Zurich, Switzerland Radiative transfer calculations in atmospheric models are computationally expensive, even if based on simplifications such as the δ-two-stream approximation. In most weather prediction models these parameterisation schemes are therefore called infrequently, accepting additional model error due to the persistence assumption between calls. This paper presents two so-called adaptive parameterisation schemes for radiative transfer in a limited area model: a perturbation scheme that exploits temporal correlations and a local-search scheme that mainly takes advantage of spatial correlations. Utilising these correlations and with similar computational resources, the schemes are able to predict the surface heating rates more accurately than a scheme based on the persistence assumption. An important property of these adaptive schemes is that their accuracy does not decrease much in case of strong reductions in the number of calls to the δ-two-stream scheme. It is hypothesised that the core idea can also be employed in parameterisation schemes for other processes and in other dynamical models. 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