1. Joe Adlhoch - Air Resource Specialists, Inc.
Review of New IMPROVE Extinction Algorithm AoH Meeting – San Diego January 24, 2006
Joe Adlhoch - Air Resource Specialists, Inc.

2. Overview
Review of proposed changes to the IMPROVE extinction algorithm
Size fractions for sulfate/nitrate/carbon
Effect of sea salt
Comparison of aerosol vs. measured light scattering
Comparison of old and new algorithm for selected WRAP sites

3. Old IMPROVE Algorithm Assumptions include that
Six particle component terms plus a constant Rayleigh scattering term are sufficient for a good estimate of light extinction;
Constant dry extinction efficiency terms for each of the six particle components works adequately for all locations and times; and
Light extinction by the individual particle components can be adequately estimated as separate terms (like externally mixed components).

4. New or Revised Terms
Variable extinction efficiencies and two additional f(RH) terms for sulfate, nitrate, and organic mass – a mixture of small and large particles is assumed
Organic Compound Mass to Organic Carbon Mass Ratio changed from 1.4 to 1.8
Addition of Sea Salt = 1.8 x [Chloride] and has its own water growth term fSS(RH)
Rayleigh Scattering is calculated for the monitoring site elevation and annual mean temperature and integer rounded. Ranges from 8 Mm-1 at 10,000’ to 12 Mm-1 at sea level
Addition of NO2 light absorption in the visible is included for sites that have such data (not routinely available at IMPROVE sites)

5. New IMPROVE Algorithm where
and nitrate and organic are split using the same process

6. Relative Humidity Enhancement Factors

7. Large/Small Species Fractions
Ammonium sulfate, ammonium nitrate, and particulate organic matter are divided into “Small” and “Large” fractions:
“Small” fraction extinction efficiency less than half that of “Large” fraction
f(RH) for “Small” fraction slightly higher
“Small” fraction dominates mass up to about 5 ug/m3
“Large” fraction dominates mass above about 12 ug/m3
Review of WRAP data shows that while high concentrations do occur, nearly all samples of these species are below 5 ug/m3

8. Large/Small Species Split
Small fraction dominates
Large fraction dominates

9. Distribution of Sulfate Concentrations

10. Distribution of Sulfate – Sequoia

11. Distribution of Sulfate – Agua Tibia

12. Distribution of Sulfate – Crater Lake

13. Distribution of Sulfate – Jarbidge

14. Distribution of Nitrate Concentrations

15. Distribution of Nitrate – Sequoia

16. Distribution of Nitrate – Agua Tibia

17. Distribution of Nitrate – Crater Lake

18. Distribution of Nitrate – Jarbidge

19. Distribution of Organic Mass Conc.

20. Distribution of OM – Sequoia

21. Distribution of OM – Agua Tibia

22. Distribution of OM – Crater Lake

23. Distribution of OM – Jarbidge

24. Review of IMPROVE Sea Salt Term
Sea salt estimated from Chloride ion measurement, Chlorine can be used as a back up
Review of 2004 data shows significant effect only at coastal sites
Review of 2000 – 2004 data timelines shows problems with Chloride measurements prior to 2004, but Chlorine appears to be a reliable back up

25. Annual Avg. Chloride Mass, 2004

26. Chloride/Chlorine Mass Timelines
Baseline\2004: median UNC ~ 0.04\0.006; median MDL ~ 0.07\0.01
Baseline: median UNC ~ <0.001; median MDL ~ 0.001

27. Chloride/Chlorine Mass Timelines
Baseline\2004: median UNC ~ 0.04\0.006; median MDL ~ 0.07\0.01
Baseline: median UNC ~ <0.001; median MDL ~ 0.001

28. Chloride/Chlorine Mass Timelines
Baseline\2004: median UNC ~ 0.08\0.05; median MDL ~ 0.07\0.01
Baseline: median UNC ~ <0.03; median MDL ~ 0.001

29. Estimated vs. Measured Light Scattering
Nephelometers provide a direct measurement of particle light scattering (extinction without elemental carbon absorption and Rayleigh scattering terms)
Comparison of estimated (aerosol) vs. measured (nephelometer) scattering possible at many IMPROVE sites
Typically, the Old IMPROVE equation underestimates extinction on very dirty days and overestimates extinction on very clean days
At most sites the New equation reduces this bias, though network-wide there is additional uncertainty
Change more dramatic with dirtier sites
Urban site (Phoenix) shows significant deviation from 1 to 1 line, may be due to poor characterization of urban haze, influence of NO2, or measurement errors
Following slides taken from work done by NPS

30. Old IMPROVE Algorithm: Estimated vs
Old IMPROVE Algorithm: Estimated vs. Observed Light Scattering for 21 Nephelometer Monitoring Sites

31. New IMPROVE Algorithm: Estimated vs
New IMPROVE Algorithm: Estimated vs. Observed Light Scattering for 21 Nephelometer Monitoring Sites

32. Site Comparison – Grand Canyon
▲ Old Equ.
● New Equ.

33. Site Comparison – Gila
Gila
▲ Old Equ.
● New Equ.

34. Site Comparison – Great Smoky Mtns.
▲ Old Equ.
● New Equ.

35. Site Comparisons – Pacific Northwest
Snoqualmie Pass
Mt. Rainier
Columbia River Gorge
Three Sisters

36. Site Comparisons – Southwest
Sycamore Canyon
Ike’s Backbone
Phoenix
Big Bend

37. Site Comparisons – Central
Jarbidge
Lone Peak

38. Summary of New Algorithm
The New algorithm incorporates new terms to more completely account for haze, incorporates updated information, and reduces know biases
Performance tests of the New algorithm show
it reduces bias compared to the Old algorithm at the extremes
it has as somewhat greater uncertainty that causes it to mis-select hazy days a little more frequently
little sensitivity to which algorithm is used with regards to composition on the extreme days
Following slides illustrate the difference between the 20% worst/best days calculated with the Old and New algorithm for selected sites

39. Selected Monitoring Locations

40. Comparison – 20% Worst Days, 2002

41. Comparison – 20% Worst Days, 2002

42. Comparison – 20% Best Days, 2002

43. Comparison – 20% Best Days, 2002

44. Implementation Steps for Regional Haze Rule Application
IMPROVE Steering Committee has approved (12/05)
Calculation of water growth functions for monthly & annual averaged conditions for each monitoring site has been completed (01/06)
Recalculation of current (5-year baseline) and natural haze levels – VIEWS – by March ???
EPA modifies the regional haze guidance, so states can choose – 6 to 12 months
VIEWS will support both versions of the algorithm for the foreseeable future