Quasi-geostrophic wave-activity conservation law
= Quasi-geostrophic wave-activity conservation law
For linear perturbations about a uniform <zonal flow>, multiplying the forced <quasi-geostrophic potential-vorticity equation> by the PV anomaly gives a local conservation law for quadratic <wave activity>. Its flux is the <Eliassen–Palm flux>, and forcing or damping appears as a wave-activity source or sink.