Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
HO 2 + NO 2 + M HNO 4 +M (10)
OH + HNO 4 H 2 O + NO 2 + O 2 (12)
Net: OH + HO 2 H 2 O + O 2
HO 2 + HO 2 + M H 2 O 2 + O 2 + M (13)
OH + H 2 O 2 H 2 O + HO 2 (14)
Net: OH + HO 2 H 2 O + O 2
NO x and HO x are therefore linked by a number of important reactions (3,9,10-12); the concentration of each depends on the concentration of the other.
2.1.2.4. The Response of Ozone to NO x in the Upper Troposphere
Figure 2-1 illustrates how the background photochemistry works to change ozone in the UT in response to variation in the concentration of NO x (Jaeglé et al., 1998).
The points are calculated from in situ measurements of HO x and NO obtained during the SUCCESS campaign. The lines show how the calculated response varies
with assumptions about HO x source strength. The response includes ozone production via reactions 4 and 5 and ozone destruction primarily via:
O 3 + HO 2 OH + 2 O 2 (15)
In all models, the net ozone production rate (production rate - loss rate) increases rapidly with NO x until a maximum is reached. At NO x concentrations larger than 500
pptv, the net rate of ozone production is expected to decrease with increasing NO x . Depending on the background concentration of NO x , additions of NO x from
aviation can increase or decrease the net ozone production rate. Thus, the background concentration of NO x determines both the magnitude and the sign of the
perturbation. Field measurements of NO x in the middle and upper troposphere typically have found NO x to be 50-200 pptv (Emmons et al., 1997; Schlager et al., 1997;
Tremmel et al., 1998). At these concentrations, the rate of net ozone production increases almost linearly with NO x .
Figure 2-1 also illustrates that the rate of ozone production depends critically on HO x source strength. In this figure, the calculation in Case 0 assumes that the primary
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