UV Dosage Levels in Summer: Increased Risk of Ozone Loss from Convectively Injected Water Vapor

The observed presence of water vapor convectively injected deep into the stratosphere over the United States can fundamentally change the catalytic chlorine/bromine free-radical chemistry of the lower stratosphere by shifting total available inorganic chlorine into the catalytically active free-radical form, ClO. This chemical shift markedly affects total ozone loss rates and makes the catalytic system extraordinarily sensitive to convective injection into the mid-latitude lower stratosphere in summer. Were the intensity and frequency of convective injection to increase as a result of climate forcing by the continued addition of CO 2 and CH 4 to the atmosphere, increased risk of ozone loss and associated increases in ultraviolet dosage would follow.