photodissociated. The computed latitude variation in total ozone is shown in Fig. 12 for two seasons. We note that the predicted changes are highly uncertain at this time (49). Figure 13 shows corresponding changes in the ozone concentration as a function of altitude. Figure 14 shows the computed changes in ozone and atomic oxygen concentrations above 40 km (25 mi). There is reasonably good agreement between the globally averaged 1-D model results and the 2-D model results. The predicted changes in mesospheric odd-oxygen species do not seem to be especially important, except perhaps with respect to chemical heating near the mesopause; reductions in O(3P) at the mesopause may lead to slightly lower mesospheric temperatures, but the magnitude of the cooling, although difficult to estimate is probably small (recall that the O concentration is smaller because the H concentration is larger, so that the overall rate of oxygen recombination via reaction cycle 17 and 30 is not altered significantly). 6. POSSIBLE CLIMATIC EFFECTS OF LARGE ROCKET OPERATIONS Changes in the mixing ratios of radiatively active minor constituents caused by HLLVs could conceivably alter atmospheric heating rates and produce climatic changes (climate here is defined narrowly as the time-averaged meteorological state at Earth's surface). At least a 10-year average would be required to obtain a representative climate that is not polluted by sampling error. Since compositional changes due to HLLVs would be confined to levels above the midstratosphere, we must look for mechanisms that could couple these higher levels with the troposphere. Such mechanisms could be radiative or dynamical. Radiative mechanisms involve perturbations of upper atmospheric composition or temperature that affect heating at the
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