Role of Deep Cloud Convection in the Ozone Budget of the Troposphere

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Abstract
Convective updrafts in thunderstorms prolong the lifetime of ozone (O3) and its anthropogenic precursor NOx [nitric oxide (NO) + nitrogen dioxide (NO2)] by carrying these gases rapidly upward from the boundary layer into a regime where the O3 production efficiency is higher, chemical destruction is slower, and surface deposition is absent. On the other hand, the upper troposphere is relatively rich in O3 and NOx from natural sources such as downward transport from the stratosphere and lightning; convective overturning conveys the O3 and NOx toward the Earth's surface where these components are more efficiently removed from the atmosphere. Simulations with a three-dimensional global model suggest that the net result of these counteractive processes is a 20 percent overall reduction in total tropospheric O3. However, the net atmospheric oxidation efficiency is enhanced by 10 to 20 percent.