85th AMS Annual Meeting

Thursday, 13 January 2005: 11:15 AM
Climatology and variability of mesoscale cyclones in the Western
Dan Lubin, SIO/Univ. Of California, La Jolla, CA
A proposed mechanism for the Western Antarctic Peninsula (WAP) warming, recently supported by GCM simulations, involves a strengthening of westerlies during high Southern Annular Mode (SAM) conditions, which blocks cold air outbreaks from the continent and allows warmer air masses to propagate into the WAP region. One possible avenue of investigation to test this hypothesis involves analyzing a multiyear record of mesoscale cyclone frequency and trajectories. Since 1989, the USAP satellite tracking facility at Palmer Station has collected and archived NOAA and U.S. Air Force polar orbiter data, at a rate of ~10 overpasses per day, that provide moderate spatial resolution (~1 km) of meteorological conditions in the WAP and Weddell Sea regions. The time resolution and spatial coverage of this multiyear satellite data set are sufficient to develop a climatology of polar mesoscale cyclones. Preliminary analysis of this imagery indicates that the WAP region experiences a normalized weekly average of 7.1 mesoscale cyclones, and that the Weddell Sea experiences a slightly smaller normalized weekly average of 5.1. However, there is substantial interannual variability in these cyclone frequencies, of order 30% for the WAP region and a factor of two for the Weddell Sea. The interannual variability in frequency and trajectories of mesoscale cyclones in both regions will be discussed in terms of concurrent variability in the SAM.

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