The effect of ozone photochemistry on atmospheric and surface temperature changes due to large atmospheric injections of smoke and NOx by a large-scale nuclear war

A coupled one-dimensional radiative-convective and photochemical diffusion model (RCP model), which takes into account the interaction of ozone photochemistry on climate, is used to investigate the possible effects of smoke and NO_x generated by a large-scale nuclear war, on vertical temperature and ozone structure and surface climate. From the results of initial experiments with fixed O₃ it is found that for the nuclear smoke injection scenario adopted in this study (similar to the base line case of Turco etal., 1983), the average sunlight intensities would be reduced drastically (up to 97%), leading to a large cooling near the surface (up to 38 K) and intense heating (up to 110 K) in the upper troposphere and lower stratosphere. Variation of surface albedo, water vapour and clouds with time following the smoke injection would further enhance the surface cooling and prolong the temperature perturbation.Further experimental results with O₃ photochemistry interaction indicate that for the smoke and NO_x nuclear injection scenario considered in this study, the total O₃ column would decrease up to 50%, with a half recovery time of about 2 y. However more than half the total O₃ column reduction is caused by the heating of the stratosphere by smoke injection. The effect of stratospheric O₃ reductions on surface climate is not significant (less than 2.5 K. additional cooling). However the vertical temperature profile is altered in such a way that it would lead to a large increase in the thermal stability of the troposphere, while decreasing it in the stratosphere more than in the case of fixed O₃. Also discussed are the solar u.v.-B flux changes at the surface which result from the presence of smoke in the atmosphere initially and from stratospheric O₃ depletions as the smoke particles are removed from the atmosphere in time.