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

• Published in: The Cryosphere
• Main Authors: van Wessem, J. M., Reijmer, C. H., Lenaerts, J. T. M., van de Berg, W. J., van den Broeke, M. R., van Meijgaard, E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2014
• Subjects: article; Verlagsveröffentlichung; East Antarctica; Antarc*; Antarctica; ice core; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-8-125-2014; https://noa.gwlb.de/receive/cop_mods_00020690; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00020645/tc-8-125-2014.pdf; https://tc.copernicus.org/articles/8/125/2014/tc-8-125-2014.pdf

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.