On the relationship between the greenhouse effect, atmospheric photochemistry, and species distribution

Abstract

A radiative‐convective‐photochemical model that extends from 0 to 53 km is used to examine the effect on atmospheric constituents and thermal structure of changes in the atmospheric levels of CO 2 , CFM's, CO, N 2 O, and combinations of these species. Calculations were carried out for two reference atmospheres, one with high (HINOX) and one with low (LONOX) levels of NO x . The HINOX atmosphere has a vertical distribution of NO x similar to that resulting from recently published measurements. Such a distribution requires an unrealistically large value for the integrated tropospheric source of NO x . This suggests that the HINOX profile, and the measurements from which it was drawn, are more characteristic of contaminated, rather than clean, air masses. The HINOX troposphere provides a net photochemical source of O 3 and is not greatly sensitive to downward transport of O 3 from the stratosphere. The LONOX troposphere is a photochemical sink for O 3 and, as a result, is sensitive to such variations in downward transport. Results of this study suggest that (1) infrared opacity changes due to CO 2 and CFM increases can cause significant changes in tropospheric O 3 , OH, CH 4 , CO, and other species through changes in tropospheric water vapor; (2) perturbation or sensitivity studies conducted with tropospheric photochemical models may be subject to significant errors due to the absence of modulating effects provided by the stratosphere; (3) the response to given perturbations is significantly dependent upon the tropospheric NO x distribution present in the model; (4) CO 2 growth rates must be included in the calculation of CFM‐O 3 time scenarios and must account for surface temperature changes, especially in the steady state; and (5) that thermal or chemical perturbations introduce a variety of coupling or interactive mechanisms which are significant and which may provide compensating effects.