Colorado Plateau Sulfate Episode

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Colorado Plateau Sulfate Episode
Worst 20 at 5 sites INGA, BRCA, MEVE, WEMI
SAPE
Best 20 at GICL, SACR, CHIR, SIAN, GUMO, TONT,
and most California sites
Clean NW CA
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Extinction Rankings for that day
Sites experiencing the worst 20 within the
Colorado Plateau
Sites experiencing the best 20 in the Colorado
Plateau and west
Precipitation at these sites
Clear skies at these sites
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Synoptic Conditions in the morning
This upper low caused high winds and blowing dust
over the area yesterday
Location of weak ridge over the area yields a
southwest flow aloft around the Colorado Plateau.
Surface winds from the S-SW in the Four Corners
in PM, variable in the AM.
This upper low still two days back
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Surface Conditions in the morning
Haze, moist airmass
Light snow in the Four Corners midnight
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Surface Conditions in the afternoon
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Cloud cover in the morning and continuing to the
afternoon at northern sites
BRCA
WEMI
MEVE
SAPE
TONT
GICL
SACR
CHIR
GUMO
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7 Day Backtrajectories from April 7, 21z
Sites that had the WORST 20 percent extinction on
that day
Mesa Verde (MEVE)
Weminuche (WEMI)
Grand Canyon (INGA)
Red10m, Blue500m, Green1500m
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SO2 emission sources
Ship lane SO2 emissions offshore
Backtrajectory path
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7 Day Backtrajectories from April 7, 21z
Sites that were in the BEST 20 percent extinction
category
Tonto (TONT)
Guadalupe (GUMO)
Gila (GICL)
Red10m, Blue500m, Green1500m
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Backtrajectories from Mesa Verde NP
Trajectories every 3 hours over the whole day
15z
21z
09z
Early morning trajectories brought parcels from a
more westerly region than the afternoon.
Basically, the trajectories still follow the
California coast out to 7 days.
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Trajectory Observations

• Sites with worst 20 extinction traveled over NE
  Arizona/NW New Mexico while those with 20 best
  didnt.
• All worst case Colorado Plateau trajectories
  traveled over southern Arizona, Phoenix and
  Tucson region within the past 12 hours.
• All but one 20 worst case area trajectory
  passed over several large SO2 sources in the Four
  Corners and eastern AZ. The Indian Gardens air
  mass came from areas directly south 12 hours
  before arriving at the monitor.

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Haze Episode Assessment

• Episode Name Colorado Plateau sulfate transport
  from regional SO2 sources?
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• Aerosol Composition at affected sites
• Colorado Plateau sites with 20 worst hazy days,
  with sulfate dominating the aerosol light
  extinction (contribution gt 40)
•  
• Spatial scale, regionality and seasonality
• Several sites in UT, NM, AZ, CO are influenced
  during the episode. Based on quick looks, most
  of these episodes are during the cool months.
•  
• Frequency and duration
•  Several sites lasted two sampling days with
  other only on that day
• Dates of other similar examples
• 4/7/2001, possibly 1/19/00, 8/25/00, 2/9/01,
  3/8/01
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• Relationship to Meteorological Conditions
•  Cool, moist airmass, flow from the south
• Source Attribution Evidence
• Large SO2 sources to the south in Arizona as well
  as ocean vessel and Southern California emissions
  are possible contributors.