Polar lows in the Labrador Sea. A case study

Abstract

In this paper, we will describe our analysis of a polar low event that occurred in the Labrador Sea during the winter of 1992. As there are unfortunately no in-situ observations of this event, we will rely on satellite data as well as the high-resolution objective analaysis from the ECMWF to document the environment in which the low developed and the structure of the low itself. We will show that the polar low developed during a cold air outbreak that was precipitated by the passage of an intense synoptic-scale low. The polar low appears to have developed along a linear cloud feature as the result of an interaction between a low-level diabatically induced potential vorticity anomaly and an upper-level potential vorticity anomaly that propagated into the area from the Canadian Arctic. We will also show that with the TOMS and TOVS retrievals for total column ozone, we are able to identify a signature of the upper-level potential vorticity anomaly. In its mature state, we will show that there were very strong winds, and as a result large fluxes of sensible and latent heat, associated with the polar low. In summary, the 1992 Labrador Sea polar low provides one with an excellent opportunity to study air-sea interactions and the coupling between the troposphere and stratosphere. The realization that the strong heating of the atmosphere and the concomitant cooling of the ocean associated with these storms may be sufficient to initiate downwelling events in the ocean may represent a hitherto undocumented link between the fast and slow climate systems that deserves further attention.