Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
The Cryosphere, 9, 1831-1844, 2015
http://www.the-cryosphere.net/9/1831/2015/
doi:10.5194/tc-9-1831-2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
18 Sep 2015
Evaluation of the updated regional climate model RACMO2.3: summer snowfall impact on the Greenland Ice Sheet
B. Noël1, W. J. van de Berg1, E. van Meijgaard2, P. Kuipers Munneke1, R. S. W. van de Wal1, and M. R. van den Broeke1 1Institute for Marine and Atmospheric research Utrecht, University of Utrecht, Utrecht, the Netherlands
2Royal Netherlands Meteorological Institute, De Bilt, the Netherlands
Abstract. We discuss Greenland Ice Sheet (GrIS) surface mass balance (SMB) differences between the updated polar version of the RACMO climate model (RACMO2.3) and the previous version (RACMO2.1). Among other revisions, the updated model includes an adjusted rainfall-to-snowfall conversion that produces exclusively snowfall under freezing conditions; this especially favours snowfall in summer. Summer snowfall in the ablation zone of the GrIS has a pronounced effect on melt rates, affecting modelled GrIS SMB in two ways. By covering relatively dark ice with highly reflective fresh snow, these summer snowfalls have the potential to locally reduce melt rates in the ablation zone of the GrIS through the snow-albedo-melt feedback. At larger scales, SMB changes are driven by differences in orographic precipitation following a shift in large-scale circulation, in combination with enhanced moisture to precipitation conversion for warm to moderately cold conditions. A detailed comparison of model output with observations from automatic weather stations, ice cores and ablation stakes shows that the model update generally improves the simulated SMB-elevation gradient as well as the representation of the surface energy balance, although significant biases remain.

Citation: Noël, B., van de Berg, W. J., van Meijgaard, E., Kuipers Munneke, P., van de Wal, R. S. W., and van den Broeke, M. R.: Evaluation of the updated regional climate model RACMO2.3: summer snowfall impact on the Greenland Ice Sheet, The Cryosphere, 9, 1831-1844, doi:10.5194/tc-9-1831-2015, 2015.
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Short summary
We compare Greenland Ice Sheet surface mass balance (SMB) from the updated polar version of the regional climate model RACMO2.3 and the previous version 2.1. RACMO2.3 has an adjusted rainfall-to-snowfall conversion favouring summer snowfall over rainfall. Enhanced summer snowfall reduce melt rates in the ablation zone by covering dark ice with highly reflective fresh snow. This improves the modelled SMB-elevation gradient and surface energy balance compared to observations in west Greenland.
We compare Greenland Ice Sheet surface mass balance (SMB) from the updated polar version of the...
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