Water vapor burden and in situ mixing ratios above and at high altitude flight levels were inferred from observations in the rotational water vapor spectral band (19.0-35.0 &mgr;m). Flight levels ranged from 15.3 to 20.0 km during 12 meridional traverses of a W-B57-F jet. The method of radiance observation, while radiometric, involved emission observations rather than absorption spectra analyses employed by McKinnon and Morewood [1971>. The flights made during September, October, November 1973 and January 1974 provide profiles of lower stratospheric water vapor by overlapping tracks from 50¿S latitude to 75¿N latitude.

The objective of the research is to describe the method of recovery of the water vapor burden and in situ mixing ratio by inference from infrared emission observations and to present the results as a latitudinal profile.