sites on a day might be characterized as those included within a relatively large arc (e.g., 120o)
whose vertex is at the center of the emissions and whose axis is the resultant wind direction.
All other sites in this example would be upwind sites.
Select air quality measures to consider at upwind and downwind sites. Since the identity
of downwind and upwind sites is a function of the resultant wind direction, individual
monitoring locations may be upwind on some days and downwind on others. Thus, to assess
relative importance of transport, it is more appropriate to look at concentrations and trends
for the group of upwind vs. the group of downwind sites rather than focus on all observations
at individual sites. We recommend looking at measures such as the highest, second highest
and spatially averaged daily maximum observed ozone concentrations at downwind vs. upwind
sites on individual days, as well as values for these variables which have been averaged over
an ozone season. In addition, we recommend looking at trends in these parameters observed
over the period between the SIP revision and the mid-course review and, perhaps, over a
longer period stretching back 10 years from the mid-course review.
Compare absolute ozone concentrations and trends at upwind and downwind sites. The
purpose of this step is to contrast ozone concentrations and trends in ozone concentrations for
each of the air quality measures selected in the previous step. This comparison is used to
judge whether transport is an important factor affecting a nonattainment area’s attainment
status. Large contrasts between upwind and downwind sites suggest that local emissions are
an important factor affecting the area’s attainment status. A mixed set of results is probably
consistent with both local emissions and transport playing a significant role. If results for
upwind and downwind monitors are nearly identical, this suggests that an area’s
nonattainment status is dominated by regional transport.
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castellano: DISPER CUSTIC DESCAR RADIA italiano:
deutsch: DIS CUS DES RAD
castellano: DIS CUS DES RAD english: DIS CUS DES RAD
português: DIS CUS DES RAD italiano: DIS CUS DES RAD
français: DIS CUS DES RAD