TROPICAL STRATOSPHERIC WATER-VAPOR MEASURED BY THE MICROWAVE LIMB SOUNDER (MLS)

The lower stratospheric variability of equatorial water vapor, measure d by the Microwave Limb Sounder (MLS), follows an annual cycle modulat ed by the quasi-biennial oscillation. At levels higher in the stratosp here, water vapor measurements exhibit a semiannual oscillatory signal with the largest amplitudes at 2.2 and 1hPa. Zonal-mean cross section s of MLS water vapour are consistent with previous satellite measureme nts from the LIMS and SAGE II instruments in that they show water vapo r increasing upwards and pole-wards from a well defined minimum in the tropics. The minimum values vary in height between the retrieved 46 a nd 22hPa pressure levels.