Capital Region Ozone Management Plan

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Capital Region Ozone Management Plan

• Preliminary Investigation of Meteorology
  Associated with Selected Ozone Exceedance Events
• Stakeholder Workshop September 25, 2008
• Erin Evans, Alberta Environment

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Why consider meteorology?

• Atmosphere controls the mixing (dispersion) and
  transport of pollutants emitted into the air
• Strongly influences air quality on any given day
• Meteorology provides the basis for predicting
  days with a high risk of reduced air quality
• An understanding of the meteorological patterns
  associated with exceedance events allows us to
  better predict days conducive to pollutant
  accumulation

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Scope of this preliminary study

• Exceedance events from 2001 through 2006
• Average conditions for the exceedance days were
  compiled and compared to the normal
  (climatological) conditions for selected
  parameters
• Heights (pressure)
• Temperature
• Wind Speed and Direction
• Precipitation Observations

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Ridge of High Pressure

• Maximum centered over Alberta/ Saskatchewan
• Typically associated with clear skies, light
  winds, negligible precipitation

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High Pressure Implications for air quality

• Vertically sinking air tends to trap pollutants
  near the surface and can lead to an accumulation
  of ozone precursors
• Also, because this sinking air suppresses cloud
  formation, clear sunny skies promote the
  photochemical production of ozone

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Warm Temperatures

• Large area experiencing warmer temperatures than
  normal
• Anomaly in excess of 6 ºC above average
• Increased temperatures promote the photochemical
  reactions forming ozone

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Wind Speed

• Region near Edmonton is experiencing slower than
  average wind speeds

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Wind Speed
Note the increased occurrence of light winds for
exceedance days
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Wind Rose Plots
Climatology
Exceedance Days
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Precipitation

• Acts to scavenge or remove air pollutants from
  the atmosphere
• There were no major precipitation events
  occurring on or immediately before an exceedance
  day
• On average, preceding an ozone exceedance day,
  there were
• 3.0 dry days (P 0 mm)
• 5.6 nearly dry days (P lt0.5 mm)

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Summary

• On average, the conditions found to be associated
  with the analyzed ozone exceedance days were
• Ridge of high pressure
• Elevated temperatures
• Slower winds with a more south to east origin
  (less west to northwest)
• No major precipitation events immediately
  preceding

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Questions?

• For further information, please contact me
• erin.evans_at_gov.ab.ca
• 403-297-5672