MAS measurements of the latitudinal distribution of water vapor and ozone in the mesosphere and lower thermosphere

We present measurements of the latitudinal variation of nighttime O₃ and H₂O in the mesosphere and (for O₃) lower thermosphere obtained with the Millimeter‐wave Atmospheric Sounder (MAS) instrument during the ATLAS 2 mission (8–15 April 1993). These are the first such measurements that have ever been reported. They indicate an O₃ mixing ratio minimum at mid‐latitudes in the upper mesosphere, with maxima in the tropics and at high latitudes. The H₂O retrievals indicate H₂O mixing ratios decreasing toward the poles in both hemispheres in the upper mesosphere. We also present measurements of the diurnal variation of O₃ at southern mid‐latitudes, at higher vertical resolution than has ever been reported previously. The results are generally consistent with previous measurements and modeling studies.