Environmental Engineering Reference
In-Depth Information
Fig. 4. Horizontal distribution of the V/N ratio (left panel) and surface temperature (C, right
panel) in the SFBA at 14 PDT on July 31, 2000
We also studied other atmospheric and chemical processes that affect ozone in
the SFBA including advection, diffusion, and dry deposition. The effect of advection
and diffusion changes from 1 h to the next both in magnitude and direction. Over
most of the eastern part of the SFBA, however, dry deposition dominates and
removes about 20-30 ppb/h ozone from the atmosphere (not shown).
The conclusions of this paper can be summarized as follows: (1) VOC and
NOx are positively correlated in the SFBA, (2) the V/N ratio is negatively cor-
related with either VOC or NOx, (3) areas of large VOC and NOx concentrations
limit ozone production while areas of small VOC and NOx concentrations promote
ozone, (4) the V/N ratio that is correlated with peak ozone production is 7, (5)
Cold sea surface temperature limits ozone production, (6) the effect of dry deposition
is significant.
3. Questions and Answers
Question: Have the authors considered the inclusion of indicator species (NOy,
HCHO/NOy) in the study? Indicator species consider the air mass aging with
respect to O 3 sensitivity and could provide additional info on O 3 formation.
Answer: We investigated 37 grid cells in depths where NOx concentrations were
around 15 ppb and VOC concentrations were around 100 ppb. Even though
these cells had similar NOx and VOC values, and similar VOC/NOx ratios, there
were large variations of O 3 production over them, ranging from −30 to +25 ppb/h.
In these cells, there was no clear correlation between NOy and O 3 production
or between HCHO/NOy and O 3 production. However, there was a slight positive
correlation between NOy-NOx and O 3 production. There was also a negative
correlation between HONO and O 3 production. We further investigated the
 
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