Update on RRFs and Hybrids

1
Update on RRFs and Hybrids

• Two meetings between EPA, CARB and the District
• Key issues -- Should Relative Reduction
  Factors be calculated by subtracting
  ozone background to net an
  anthropogenic emissions reduction
  factor
• -- Would hybrid meteorological models
  be accepted as a valid methodology

July 12, 2006
2
RRFs

• EPAs method RRFs are calculated using
  baseline current and future emissions
• Background ozone 40 ppb
• Relative anthropogenic reduction is greater
  percentage when background is subtracted
• EPAs position recognize in some cases such as
  the Basin, unique approaches may be required
  prefer the guideline approach but the issue is
  still pending further discussion

3
Hybrid Meteorological Modeling

• SoCAB has two distinct ozone basin maximum
  locations with complex terrain
• Transport to SCLR requires the winds to rotate
  against the typical westerly flow
• Dynamic models tendency to shift transport to
  east, midday missing SCLR
• Previous AQMP modeling analyses used objective
  analysis and hybrids
• EPAs position encourage use of dynamic-mass
  consistent approach hybrids may perform better
  in specific applications such as complex
  terrain, use the best tool available