SPACE-BORNE H2O OBSERVATIONS IN THE ARCTIC STRATOSPHERE AND MESOSPHERE IN THE SPRING OF 1992

We report on stratospheric and mesospheric water vapor (H2O) observati ons obtained by the Millimeter wave Atmospheric Sounder (MAS) in the A rctic spring of 1992. In the lower stratosphere, the observations show enhanced H2O inside the vortex between 450 K and 625 K, in agreement with other H2O observations. In the upper stratosphere and lower mesos phere, at potential temperatures between 1850 K and 2200 K, we find re gions of depressed H2O volume mixing ratio coincident with remnants of high potential vorticity. The depressed mesospheric H2O, as well as t he enhanced lower stratospheric H2O, are consistent with wintertime de scent. It also suggests effective containment of air up into the lower mesosphere.