Determination of the altitude of the nitric acid layer from very high resolution ground-based IR solar spectra

A ground-based solar spectrum at a spectral resolution of about 0.002/cm is used to determine the altitude of the HNO3 layer. The 870/cm spectral region, which is essentially free from absorptions from other species, is employed. The data were obtained with the University of Denver 2.5-m maximum path difference Fourier Transform interferometer spectrometer system. A set of 13 HNO3 vertical profiles were used in the analysis. The best fit obtained for the 'starting' profile (which is centered at 24 km), and the best fit for the profile centered at 26 km are shown. For displacements of greater than 2 km, the discrepancy between the synthetic and observed spectra becomes readily discernible by inspection of the spectra. It is shown that the 'best fit' rms residuals are quite sensitive to the assumed altitude of the HNO3 layer.