Stratospheric sounding by infrared heterodyne spectroscopy

Abstract

Intensity profiles of infrared spectral lines of stratospheric constituents can be fully resolved with a heterodyne spectrometer of sufficiently high resolution (∼5 MHz or 0.000167 cm−1 at 10 µ). The constituents' vertical distributions can then be evaluated accurately by analytic inversion of the measured line profiles. Estimates of the detection sensitivity of a heterodyne receiver are given in terms of minimum detectable volume mixing ratios of stratospheric constituents, indicating a large number of minor constituents which can be studied. Stratospheric spectral line shapes and the resolution required to measure them are discussed in light of calculated synthetic line profiles for some stratospheric molecules in a model atmosphere. The inversion technique for evaluation of gas concentration profiles is briefly described, and applications to synthetic lines of O3, CO2, CH4, and N2O are given. Some recent heterodyne measurements of CO2 and O3 absorption lines are analytically inverted, and the vertical distributions of the two gases are determined.

Stratospheric ozone measurement with an infrared Heterodyne spectrometer

“…Diode laser heterodyne spectra of atmospheric 03 at a resolution of 70 MHz have also been reported (Frerking and Muehiner, 1977) and altitude profiles have been derived (Abbas et al 1977)o…”

“…The use of a C02 laser as a local oscillator limits atmospheric measurements to those lines which lie within the electrical bandwidth (±+1.5 GHz) of the photomixer. A more detailed description of the instrument, of its advantages, and of its limitations has been given elsewhere (Abbas, et al 1976(Abbas, et al , 1977Mumma, et al …”

“…This may be done trivially if the mirror-side band has no absorption lines and the continuum has the same level in both sidebands. Inversion of observed spectral lines may then be carried out in the usual way (Abbas, et al 1977). …”

“…The observed 0 line (Fig. 2) was inverted using the radiative 3 transfer methods discussed elsewhere (Abbas, et al 1977). Suitable weighting functions based on this line alone cover a range of altitudes from -10-30 km (Fig.…”

Thermal infrared laser heterodyne spectroradiometry for solar occultation atmospheric CO<sub>2</sub> measurements

“…The heterodyne technique, using diode or (CO 2 ) gas lasers and only much later using QCLs, had successfully been applied to ground-based studies of the Earth's atmosphere (e.g. Abbas et al, 1979;Fast et al, 2004;Glenar et al, 1982;Koide et al, 1995;Menzies and Seals, 1977) and that of other solar system bodies (Kostiuk et al, 1977(Kostiuk et al, , 2001e.g. Kostiuk, 1994;Sonnabend et al, 2006), in terms of composition, structure, and dynamics, as well as in other areas of astronomy.…”