Potential vorticity in the stratosphere derived using data from satellites

Abstract

Abstract Maps of Ertel's potential vorticity, Q , are computed on an isentropic surface in the middle of the stratosphere. They are derived using data from stratospheric sounding units on board NOAA satellites. the reliability of the maps is demonstrated mainly by conservation of Q that is shown in successive analyses, and by the close agreement obtained using independent data from two satellites. The maps are used to follow the movement of material during the course of strong disturbances which occurred in December 1981. They clearly show the breaking of planetary waves in the stratosphere, an inherently nonlinear process. the effect of wave breaking on the structure of the westerly vortex is considered. Any mixing of Q on isentropic surfaces during wave breaking is shown to be far from complete in the examples studied. The behaviour of diagnostics based on zonal averaging, such as the Eliassen‐Palm flux, is accounted for by local changes in the distribution of Q . the implications of our findings for the study of stratospheric dynamics are discussed.