Mesoscale Structure of Cape Farewell Tip Jets

Abstract

ape Farewell, Greenland?s southernmost point, is characterized by a number of low-level jets that are the result of topographic flow distortion associated with passing extratropical cyclones. The heavy seas associated with these wind events are a hazard to maritime traffic in the region. In addition, the air?sea heat flux associated with these weather systems plays an important role in the climate system by contributing to the forcing of the lower limb of the Atlantic meridional overturning circulation. In this paper, the North American Regional Reanalysis will be used to generate a higher-resolution climatology of these mesoscale jets as compared to previous studies. Through the use of a diagnostic that partitions the occurrence frequency of high-speed wind events by wind direction, the author shows that there are four different types of Cape Farewell tips jets that are characterized as having either northwesterly, southwesterly, northeasterly, or southeasterly wind direction. All four types have distinct regions in the vicinity of Cape Farewell where their respective occurrence frequencies and air?sea heat fluxes are at a maximum. The southwesterly and northeasterly jets closely resemble the wind systems previously identified as being westerly and easterly tip jets. There are also instances where one type evolves into another and so it is possible to view westerly tip jets as a continuum with the northwesterly and southwesterly events identified in this paper representing end members with a similar picture for easterly tip jets. The position of a particular event along these continua will determine its impact on local weather and the coupled climate system.