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Variations in the tropical uplift following the Pinatubo eruption studied by infrared solar absorption spectrometry

Infrared solar absorption spectra of atmospheric trace gases were measured during a ship cruise in October 1996 between 57°N and 45°S. The abundances of stratospheric species are compared with those derived from NASA DC‐8 aircraft spectra from spring 1992, recorded seven months after the Pinatubo eruption. We examine column abundances of HCl, HF and HNO3 to study variations in the tropical uplift, following the enhanced aerosol loading. The comparison yields a vertical shift in the mixing ratio profiles of HCl and HF of less than 1 km at 25 km altitude (Post Pinatubo versus 1996), which is of the same order of magnitude as the known seasonal, longitudinal and year‐to‐year variabilities of the tropical uplift. The results suggest that long term pertubations following the eruption, like the observed long term ozone reduction at midlatitudes, are mainly chemical in nature rather than the result of sustained dynamical pertubations.