The determination of HNO3 column amounts from tunable diode laser heterodyne spectrometer spectra taken at Jungfruajoch, Switzerland

In May of 1991 a tunable diode laser heterodyne spectrometer built by the National Physical Laboratory was operated at the International Scientific Station of the Jungfraujoch (46.5 deg N, 8.0 deg E, altitude 3.56 km). Nitric acid spectra in the region of 868 wavenumbers were recorded at sunset and sunrise on two separate days at a resolution of 0.0013 wavenumbers with a signal-to-noise ratio of approximately 130:1. A vertical column amount of HNO3 of 1.61 x 10(exp 16) molecules/sq cm was determined using an atmospheric transmission model developed at the University of Denver. The mean of a number of mid-latitude, northern hemisphere profiles was used as the initial profile for the inversion. A comparison of different initial profiles provides information on the sensitivity of the retrieved column amount of 1.61 x 10(exp 16) molecules/sq cm lies within the range of values published in the World Meteorological Organization Report no. 16 (1986), but is considerably larger than the value of (0.99 - 1.29) x 10(exp 16) reported by Rinsland et al. (1991) for June during the period 1986 to 1990.