An assessment of a Greenland lee cyclone during the Greenland Flow Distortion experiment: An observational approach

Abstract

AbstractOn 3 March 2007 between 0920 and 1545 UTC, the mesoscale structure of a mature lee cyclone southeast of Greenland was successfully captured during a flight with a research aircraft during the Greenland Flow Distortion experiment (GFDex). The cyclone was accompanied by hazardous weather conditions such as extensive icing and low‐level wind speeds exceeding 34 m s−1. Calculations based on atmospheric soundings from Egedesminde on the west coast of Greenland indicate that conditions were favourable for flow splitting and hence cyclogenesis in the lee of Greenland during the formation of the cyclone. PV inversion carried out on an upper‐level southward‐moving potential vorticity (PV) anomaly indicates that upper‐level forcing as well as orographic forcing had an important role in the cyclone development. The frontal seclusion of the cyclone's warm core was consistent with both the Norwegian cyclone model and Shapiro and Keyser's model. However, it was not possible to match this cyclone precisely with any of these models, which is probably a consequence of the strong influence from Greenland on the cyclone development. In situ measurements showing a combination of warm dry air with relatively high ozone concentrations in the centre of the cyclone together with trajectory calculations indicate that this air had experienced considerable descent, probably induced by Greenland's orography. The observations documented the cyclone's mesoscale structure, and clearly revealed a deep tropopause fold. This tropopause fold is a manifestation of the forcing on the cyclone from the upper‐level PV anomaly. Copyright © 2009 Royal Meteorological Society