A diagnostic Study of Baroclinic Disturbances in Polar Air Streams.
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Model-generated data and FGGE analyses are used to calculate quasi-Lagrangian budgets of mass, vorticity, heat and moisture following disturbances that form within polar air streams. These polar lows grow primarily through basic baroclinic instability processes and exhibit many features of larger maritime extratropical cyclones. Polar lows that originate on the equatorward side of a nearly straight upper-level jet are contrasted with lows that form on the poleward side of the jet and have considerable midtropospheric positive vorticity advection at formation time. The absence of favorable coupling to a jet stream was the missing factor in two model-generated polar lows that failed to develop. Although the vorticity balance is initially different for the two types of polar lows, the vorticity budgets during later stages are similar. The heat budget and the thickness tendency equation demonstrate that the self-development process that is present in larger maritime cyclones is also important for polar low intensification. Author