Measurements of submillimetre wavelength radiation emitted by the stratosphere

Observations have been made of the submillimetre wavelength radiation emitted by the lower stratosphere, using techniques of Fourier transform spectroscopy, while flying in a Comet 2E aircraft. Using the method of phase‐modulation high quality spectra have been obtained at several altitudes over the spectral range 20 to 66 cm −1 , and these have enabled identification of many emission lines due to O 2 and O 3 , in addition to those of H 2 O. Also several unidentified emission lines have been observed. The meteorological applications of this spectroscopic technique are considered. In particular, a direct method of comparing the emission of ‘strong’ water‐vapour and oxygen lines enables a calculation of mixing ratio of water vapour in the stratosphere to be made, and a value of (2.1 ± 0.3) × 10 −6 g/g is derived above an altitude of 12.2 km. A similar comparison for ozone has given an integrated concentration of 0.35 ± 0.10 cm atm in the vertical path above the observer. The merits of these observations in measuring stratospheric mixing ratios are discussed with respect to alternative techniques, in particular with reference to balloon‐borne studies.