Spectroscopic observations of atmospheric trace gases over Kitt Peak: 3. Long‐term trends of hydrogen chloride and hydrogen fluoride from 1978 to 1990

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Abstract
We have analyzed solar spectra obtained with the 1‐m Fourier transform spectrometer and the 13.5‐m spectrograph at the McMath telescope on Kitt Peak for absorption by hydrogen chloride and hydrogen fluoride which are largely confined to the stratosphere. During the period 1978–1990 we find that the amounts of both species have been increasing significantly; HCl at a rate of 1.0×1014 mol cm−2 yr−1 and HF at a rate of 0.37×1014 mol cm−2 yr−1. Referred to 1984 values, these rates correspond to increases of 6% yr−1 for HCl and 9% yr−1 for HF, or a factor of 2 for HCl and a factor of 3 for HF for the 12‐year period. These fractional increases are comparable to the published increases in the ground level concentrations of the halocarbons. Both gases show complicated patterns of variability superimposed on seasonal signatures. However, the tight correlation between the HCl and HF amounts is further clear evidence that a single mechanism is primarily responsible for the variability of these gases. Exceptions may be the pronounced short‐lived maxima noted in February 1982 and in February 1990 which correlate with the ash clouds from the Nyamuragira and Redoubt volcanos.