1 / 12

Diagnostic Ozone Sensitivity Tests the St. Louis 8-Hour Ozone and PM 2.5 Study

Diagnostic Ozone Sensitivity Tests the St. Louis 8-Hour Ozone and PM 2.5 Study. Ralph Morris, Ou Nogmoncol, Abby Hoats, Gerry Mansell and Chris Emery ENVIRON International Corporation St. Louis 8-Hour Ozone/PM 2.5 Workgroup Meeting March 20, 2006. Background.

hayley
Download Presentation

Diagnostic Ozone Sensitivity Tests the St. Louis 8-Hour Ozone and PM 2.5 Study

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Diagnostic Ozone Sensitivity Tests the St. Louis 8-Hour Ozone and PM2.5 Study Ralph Morris, Ou Nogmoncol, Abby Hoats, Gerry Mansell and Chris Emery ENVIRON International Corporation St. Louis 8-Hour Ozone/PM2.5 Workgroup Meeting March 20, 2006

  2. Background • Phase I of the St. Louis 8-Hour Ozone and PM2.5 Study developed three 8-hour ozone episodes for the CAMx and CMAQ models • Working with the Four Modeling Hubs, the episodes were evaluated • Ozone performance characterized by a general underestimation bias • CAMx was performing better than CMAQ • Given time constraints, Modeling Hubs decided to focus on the CAMx model for 8-hour ozone

  3. Background • Ozone underestimation tendency • St. Louis urban core ozone hole overstated • Modeled ozone formation too slow so that peaks occur further downwind than observed • Magnitudes of the peaks comparable to observed • Potential causes of ozone performance • Insufficient sunlight intensity • Insufficient vertical mixing • Too little VOC in StL • Too much NOx in StL • Other???

  4. Sensitivity Tests • Analyze MM5 cloud estimates to see if excessive – attenuates photolysis rates • Perform sensitivity tests • Base 3 w/ Mech 3 (compare with Mech4) • Kz_min =1.0 m2/s • Kvpatch with Kz_min =2.0 m2/s • 1.5 x ISOP (biogenic) • 1.5 x non-ISOP VOC (anthropogenic) • 0.75 x NOx (anthropogenic)

  5. 8-hr Ozone June 21, 2002 CAMx Mech 4 Base 2

  6. 8-hr Ozone July 15, 2002 CAMx Mech 4 Base 2

  7. Example Cloud EvaluationFairly Good Agreement – No Over-statement MM5 Predicted Satellite

  8. June/July Episode Sensitivity • Mech 3: Norm Bias = -13% to -38% • Mech 4: Norm Bias = -9% to -32% • Mech 4 improves Bias by 2-5 percentage points • Likely due to renoxification reaction • Kzmin = 2.0 m2/s • Improves bias by ~2 percentage points

  9. June/July Episode Sensitivity • Mech 3 & Kzmin=2: Norm Bias –12% to –36% • 1.5 x Biogenic Isoprene Emissions • Improvement in June (south wind) episode with Norm Bias increasing 3-5 percentage points • Little effect for July episode • 0.75 x Anthropogenic NOx Emissions • Little effects (Norm Bias <+2% change) • Urban ozone increases offset by rural ozone reductions • 1.5 x Anthropogenic VOC Emissions • Minor (1 percentage point increase) improvements

  10. Base 3 Mech 3 Kz_min=2.0 1.5 x ISOP 0.75 x NOx June 21, 2002 Daily Maximum 8-Hour Ozone (ppb)

  11. Kz_min=2.0 Base 3 Mech 3 0.75 x NOx 1,5 x ISOP July 15, 2002 Daily Maximum 8-Hour Ozone (ppb)

  12. Emission Sensitivity Tests • 1.5xISOP emissions sensitivity buys about 5% points in bias for June 21, little effect on July 15 • June 21 has transport from south where high biogenic isoprene occurs • Supports rerunning biogenic emissions with MM5 temperatures adjusted to correct bias • 0.75xNOx & 1.5xnon-ISOP VOC less of an effect • Although overstated low-level NOx in urban core could still be part of the problem

More Related