The Role of Wave Dynamics and Small-Scale Topography for Downslope Wind Events in Southeast Greenland.

Oltmanns, Marilena , Straneo, F., Seo, H. and Moore, G. W. K. (2015) The Role of Wave Dynamics and Small-Scale Topography for Downslope Wind Events in Southeast Greenland. Open Access Journal of the Atmospheric Sciences, 72 (7). pp. 2786-2805. DOI 10.1175/JAS-D-14-0257.1.

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Abstract

In Ammassalik, in southeast Greenland, downslope winds can reach hurricane intensity and represent a hazard for the local population and environment. They advect cold air down the ice sheet and over the Irminger Sea, where they drive large ocean–atmosphere heat fluxes over an important ocean convection region. Earlier studies have found them to be associated with a strong katabatic acceleration over the steep coastal slopes, flow convergence inside the valley of Ammassalik, and—in one instance—mountain wave breaking. Yet, for the general occurrence of strong downslope wind events, the importance of mesoscale processes is largely unknown. Here, two wind events—one weak and one strong—are simulated with the atmospheric Weather Research and Forecasting (WRF) Model with different model and topography resolutions, ranging from 1.67 to 60 km. For both events, but especially for the strong one, it is found that lower resolutions underestimate the wind speed because they misrepresent the steepness of the topography and do not account for the underlying wave dynamics. If a 5-km model instead of a 60-km model resolution in Ammassalik is used, the flow associated with the strong wind event is faster by up to 20 m s−1. The effects extend far downstream over the Irminger Sea, resulting in a diverging spatial distribution and temporal evolution of the heat fluxes. Local differences in the heat fluxes amount to 20%, with potential implications for ocean convection.

Document Type: Article
Keywords: Katabatic winds; Severe storms; Air-sea interaction; Mesoscale processes; Orographic effects; Model evaluation/performance
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1175/JAS-D-14-0257.1
ISSN: 0022-4928
Date Deposited: 10 Jan 2018 13:00
Last Modified: 08 Jan 2019 12:46
URI: http://oceanrep.geomar.de/id/eprint/41370

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