Impact of surface characteristics on flow over a mesoscale mountain

• Published in: Quarterly Journal of the Royal Meteorological Society
• Main Authors: Jonassen, Marius O., Ágústsson, Hálfdán, Ólafsson, Haraldur
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: Hofsjökull; Ice cap; Iceland
• Online Access: http://dx.doi.org/10.1002/qj.2302; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fqj.2302; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.2302

Dynamical downscaling of atmospheric flow over Iceland has revealed that prominent downslope accelerated flows are not merely extreme events, but rather constitute a strong climatological signal over the larger ice caps. Ice caps are characterised by smooth and cold surfaces and both of these properties have previously been found to enhance downslope flows. In this article, we investigate the response of downslope accelerated flow over Hofsjökull in Central Iceland to an increase in surface roughness and a change in surface temperature corresponding to the effect of melting Hofsjökull's ice cap. We do so by exploring the flow over Hofsjökull for a summertime case by means of several numerical sensitivity experiments. In the experiments, we find a stronger downslope flow acceleration with than without the ice cap. While an increased surface roughness distinctly dampens the downslope flow, the effect of changing the surface temperature is minimal. This study is both of general relevance through its exploration of factors affecting downslope acceleration of stably stratified flow and also of interest because glaciers diminish rapidly in a changing climate.