ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-7-5659-2007 Two adaptive radiative transfer schemes for numerical weather prediction models Venema V. 1 Schomburg A. 1 Ament F. 1 2 Simmer C. 1 Meteorologisches Institut, Universität Bonn, Auf dem Hügel 20, 53121 Bonn, Germany Meteo Schweiz, Numerical Models, Kraehbuehlstrasse 58, 8044 Zurich, Switzerland 15 11 2007 7 21 5659 5674 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/7/5659/2007/acp-7-5659-2007.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/7/5659/2007/acp-7-5659-2007.pdf

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 net radiative fluxes 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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