987 Synoptic-Dynamic Climatology of the Stratospheric Aleutian Anticyclone

Wednesday, 25 January 2017
Stephen J. Colucci, Cornell University, Ithaca, NY; and T. E. Ehrmann

Handout (746.0 kB)

While the first author (SJC) was an undergraduate student at the University at Albany, working part-time shelving books in the University library for less than minimum wage, he approached Professor Lance Bosart (LFB) and asked if he could do more meaningful (and maybe, but not necessarily, more financially lucrative) work.  LFB then assigned SJC to a project that involved evaluating the accuracy of currently operational forecasting models at predicting surface anticyclones.  This lead to a co-authored paper (Colucci and Bosart, MWR, 1979) and a life-long fascination by SJC with anticyclones.

     Today the anticyclonic obsession by SJC is with the "Aleutian High", a prominent feature of the wintertime, stratospheric Northern Hemisphere circulation about which surprisingly little has been written.  It is not even clear why there is an Aleutian High, although we reasonably well understand its cyclonic counterpart, the stratospheric polar vortex.  To address this deficiency in our knowledge of the large-scale atmospheric circulation, we are constructing a synoptic-dynamic climatology of the Aleutian High.  Employing a novel vortex identification metric developed by the second author (TSE), we have determined the spatial and temporal distribution of stratospheric Aleutian anticyclones in a large dataset.  We have further explored the composite dynamics of this system with a potential vorticity inversion technique.  Prelimimary results as of this writing reveal that the Aleutian High is driven by stratospheric (rather than tropospheric), thermal (rather than mechanical) processes.  We will be further investigating the relationship between the Aleutian High and anomalous distortions of the polar vortex during sudden stratospheric warmings (reversals of the zonal mean zonal flow from westerly to easterly in the midlatitude stratosphere).

     SJC will report these findings, originally inspired by LFB over 40 years ago.

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