Updated cloud physics in a regional atmospheric climate model improves the modelled surface energy balance of Antarctica

van Wessem, J. M.; Reijmer, C. H.; Lenaerts, J. T. M.; van de Berg, W. J.; van den Broeke, M. R.; van Meijgaard, E.

In this study the effects of changes in the physics package of the regional atmospheric climate model RACMO2 on the modelled surface energy balance, near-surface temperature and wind speed of Antarctica are presented. The physics package update primarily consists of an improved turbulent and radiative flux scheme and a revised cloud scheme that includes a parameterisation for ice cloud super-saturation. The ice cloud super-saturation has led to more moisture being transported onto the continent, resulting in more and optically thicker clouds and more downward long-wave radiation. Overall, the updated model better represents the surface energy balance, based on a comparison with >750 months of data from nine automatic weather stations located in East Antarctica. Especially the representation of the turbulent sensible heat flux and net long-wave radiative flux has improved with a decrease in biases of up to 40%. As a result, modelled surface temperatures have increased and the bias, when compared to 10 m snow temperatures from 64 ice-core observations, has decreased from −2.3 K to −1.3 K. The weaker surface temperature inversion consequently improves the representation of the sensible heat flux, whereas wind speed biases remain unchanged. However, significant model biases remain, partly because RACMO2 at a resolution of 27 km is unable to resolve steep topography.

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van Wessem, J. M. / Reijmer, C. H. / Lenaerts, J. T. M. / et al: Updated cloud physics in a regional atmospheric climate model improves the modelled surface energy balance of Antarctica. 2014. Copernicus Publications.

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Rechteinhaber: J. M. van Wessem et al.

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