Free tropospheric ozone production following entrainment of urban plumes into deep convection

Simulation of convective redistribution and subsequent photochemistry of an urban plume from Oklahoma City during the 1985 PRESTORM campaign shows enhancement of O₃ production in the free tropospheric cloud outflow layer by a factor of almost 4. In contrast, simulation of convective transport of an urban plume from Manaus, Brazil, into a pristine free troposphere during GTE/ABLE 2B (1987), followed by a photochemical simulation, showed enhancement of O₃ production by a factor of 35. Convective transport of ozone precursors to the middle and upper troposphere allows the resulting O₃ to spread over large geographic regions, rather than being confined to the lower troposphere where loss processes are much more rapid. Conversely, as air with lower NO descends and replaces more polluted air, there is greater O₃ production efficiency per molecule of NO in the boundary layer following convective transport. As a result, over 30% more ozone could be produced in the entire tropospheric column in the first 24 hours following convective transport of urban plumes. -from Authors