A Climatology of Wintertime Barrier Winds off Southeast Greenland

Abstract

climatology of barrier winds along the southeastern coast of Greenland is presented based on 20 yr of winter months (1989?2008) from the ECMWF Interim Reanalysis (ERA-Interim). Barrier wind events occur predominantly at two locations: Denmark Strait North (DSN; 67.7°N, 25.3°W) and Denmark Strait South (DSS; 64.9°N, 35.9°W). Events stronger than 20 m s?1 occur on average once per week during winter with considerable interannual variability?from 7 to 20 events per winter. The monthly frequency of barrier wind events correlates with the monthly North Atlantic oscillation (NAO) index with a correlation coefficient of 0.57 (0.31) at DSN (DSS). The associated total turbulent heat fluxes for barrier wind events (area averaged) were typically about 200 W m?2 with peak values of 400 W m?2 common in smaller regions. Area-averaged surface stresses were typically between 0.5 and 1 N m?2. Total precipitation rates were larger at DSS than DSN, both typically less than 1 mm h?1. The total turbulent heat fluxes were shown to have a large range as a result of a large range in 2-m air temperature. Two classes of barrier winds?warm and cold?were investigated and found to develop in different synoptic-scale situations. Warm barrier winds developed when there was a blocking high pressure over the Nordic seas, while cold barrier winds owed their presence to a train of cyclones channeling through the region.