This article is from the Ozone Depletion: Stratospheric Chlorine and Bromine FAQ, by Robert Parson rparson@spot.colorado.edu with numerous contributions by others.
Since the stratosphere is very dry, water-soluble compounds are
not quickly washed out as they are in the troposphere. The
stratospheric lifetime of HCl is about 2 years; the principal
sink is transport back down to the troposphere.
 
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