3-DIMENSIONAL EVOLUTION OF WATER-VAPOR DISTRIBUTIONS IN THE NORTHERN-HEMISPHERE STRATOSPHERE AS OBSERVED BY THE MLS

The three-dimensional evolution of stratospheric water vapor distribut ions observed by the Microwave Limb Sounder (MLS) during the period Oc tober 1991-July 1992 is documented. The transport features inferred fr om the MLS water vapor distributions are corroborated using othe dynam ical fields, namely, nitrous oxide from the Cryogenic Limb Array Etalo n Spectrometer instrument, analyzed winds from the U.K. Meteorological Office (UKMO), UKMO-derived potential vorticity, and the diabatic hea ting field. By taking a vortex-centered view and an along-track view, the authors observe in great detail the vertical and horizontal struct ure of the northern winter stratosphere. It is demonstrated that the w ater vapor distributions show clear signatures of the effects of diaba tic descent through isentropic surfaces and quasi-horizontal transport along isentropic surfaces, and that the large-scale winter flow is or ganized by the interaction between the westerly polar vortex and the A leutian high.