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San Antonio as in Austin. Corpus Christi and Victoria also show substantial
impact in this case in comparison to the case where ozone is greater than
84 ppb. This illustrates the increasing need of considering climate change
scenarios while evaluating the impact of a tighter ozone standard.
4.5 . Number of 8-h ozone exceedances
The impact of temperature perturbations on the surface ozone concentra-
tions was also determined by computing the total number of 8-h averaged
ozone exceedances over the entire 4 km modeling domain over the episodic
period for each of the temperature perturbation scenarios. Although the
number of exceedances has decreased substantially in the future case in
comparison to the base case, with rising temperatures, the number of
exceedances shows a significant increase. The first 2 C rise in temperature
causes a large increase in the 4 km modeling domain for both the cutoff
values ( > 84 ppb and > 74 ppb), as shown in Tables 6 and 7. Subsequently, the
increase in the number of 8-h ozone exceedance events is more moderate with
respect to the immediately preceding temperature perturbation scenario.
This analysis emphasizes the fact that the temperature perturbations affect
Table 6.
Number of ozone exceedances ( > 84 ppb).
Perturbed temperature
Future case
+2 C+
C+
C+
C+
C
Austin
0
0
19
68
163
263
San Antonio
18
125
183
254
302
368
Corpus Christi
0
0
1
20
36
69
Victoria
0
0
0
0
0
0
Entire domain
18
171
282
462
711
1124
Table 7.
Number of ozone exceedances ( > 74 ppb).
Perturbed temperature
+2 C+ C+ C+ C+ C
Future case
Austin
178
1406
2235
3076
3934
4858
San Antonio
413
1007
1186
1384
1594
1852
Corpus Christi
115
362
463
566
653
741
Victoria
0
131
291
482
631
786
Entire domain
1171
6690
10348
14441
18685
23035
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