Interaction of cold-air blocking and upper-level potential vorticity anomalies during lee cyclogenesis

Joseph Egger

doi:10.3402/tellusa.v47i5.11550

Interaction of cold-air blocking and upper-level potential vorticity anomalies during lee cyclogenesis

Tellus

Volume 47 (1995): Issue 5

By: Joseph Egger

Open Access

|Jan 1995

Abstract

A two-dimensional model of the interaction of cold-air blocking by a mountain and of an anomaly of potential vorticity (PV) moving over the mountain during lee cyclogenesis, is presented. The model is based on the semigeostrophic equations for a three-layer atmosphere with piecewise constant distributions of potential vorticity. A geostrophic mean flow U normal to the mountain is imposed. Initially, an upper-level PV-anomaly is assumed above a cold layer confined by a surface front. The near-surface circulation is anticyclonic underneath the anomaly. Both the front and the anomaly move with speed ~ U towards the mountain, where the cold air is blocked while the anomaly crosses the mountain and induces a cyclone in the lee.

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