Aspects of Potential vorticity dynamics: inversions and attribution
Prof. Joseph Egger
LMU Munchen, Germany
Inversion seeks to determine the complete flow if just one variable q1 is available. A balance condition is needed and boundary conditions must be specified. The concept of attribution relates to the choice of PV for q1. Attribution claims that PV has an influence on the flow. This idea is often illustrated by the electrostatics where PV anomalies are seen as analogues of electric charges. These ideas are discussed and exposed to a counter example. Piecewise PV inversion (PPVI) seeks to determine this impact of observed PV anomalies on the surrounding flow. A flow domain D is divided in subdomains D1 and D2 (D - D1). The PV in D1 to the resulting flow with stream function s is not unique because there are many anomalies in D1 which induce the same s. On the other hand, the superposition principle is violated in this case. The relevance of these results for the concept of attribution is discussed.