A photochemical model has been used to quantify the sensitivity of the tropospheric oxidants O3 and OH to changes in CH4, CO and NO emissions and to perturbations in climate and stratospheric chemistry. Coefficients of the form ∂1n[O3]/∂1n[X] and ∂1n[OH]/∂1n[X], where [X] = flux of CH4, CO, NO; stratospheric O3 and H2O have been calculated for a number of "chemically coherent" regions (e.g. nonpolluted continental, nonpolluted marine, urban) at low and middle latitudes. Sensitivities in O3 and OH vary with regional emissions patterns and are nonlinear within a given region as [X] changes. In most cases increasing CH4 and CO emissions will suppress OH (negative coefficients) and increase O3 (positive coefficients) except in areas where NO and O3 influenced by pollution are sufficient to increase OH. Stratospheric O3 depletion will tend to decrease O3 (except in high NOx areas) and increase OH through enhanced u.v. photolysis. Increased levels of water vapor (one possible outcome of a global warming) will also decrease O3 and increase OH. We conclude that in most regions, NO, CO and CH4 emission increases will suppress OH and increase O3, but these trends may be opposed by stratospheric O3 depletion and climate change. A regional survey of OH and O3 levels suggests that the tropics have a pivotal role in determining the earth's future oxidizing capacity.
All Science Journal Classification (ASJC) codes
- General Environmental Science
- General Earth and Planetary Sciences