Update on Natural Levels II Technical Review Committee By Marc Pitchford for the June 12 th RPO Monitoring/Data Analysis Conference Call

Overall Objective: To agree on a methodology that estimates the worst and best natural conditions for each monitoring site for use with current conditions estimated by the new IMPROVE algorithm so that Regional Haze Rule glide paths can be calculated in a consistent way for states that wish to use the new algorithm.

Concerns Raised: 1.The new IMPROVE algorithm uses concentrations in an empirical approach to determine how much of the sulfate, nitrate, and organic concentrations should be in the large and small size distributions. We should assume that natural conditions have both large and small size distributions in about the same frequency but with (possibly) much lower concentrations. 2.All components of aerosol extinction should be scaled to Trijonis' natural values in a consistent manner. 3.Use of the baseline (2000 to 2004) to estimate site specific haze distribution functions (i.e. the standard distributions) on a site by site basis is liable to give distortions because one of the years had very unusual fire impacts at a number of western sites thereby giving a false sense of the width of the distributions. 4.We should check that the best day natural haze estimates at each site are consistent with the current best days (i.e. they shouldn't be larger than current best days).

Further modifications to natural condition estimates 1.Use scattering efficiencies as prescribed by the new IMPROVE algorithm natural scenario “N” 2.Test the effect of basing natural mass concentrations on current values. Assume 80% of current OMC is natural Test the effect of using current OMC, EC, fine soil, and CM on G90 dv natural estimates Look at the difference between current mean mass concentrations and naturals estimates by aerosol species

Scenarios where individual aerosol species mass is adjusted from natural estimates to current levels N – uses Trijonis east/west mass concentrations N1 – scale only SO4 and NO3 to estimated natural mass concentrations (presentation 5) N2 – scale only SO4, NO3 and EC to estimated natural mass concentrations (presentation 5) N3 – OMC adjusted to 80% of current mean N4 – OMC = current mean N5 – EC = current mean N6 – fine soil = current mean N7 – coarse mass = current mean N8 – fine soil and CM = current mean Sensitivities of scenario N to scenarios N3…N8 Mass adjustments (current to natural estimate mean mass shifts)

Scale aerosol mass frequency distributions Sipsey Alabama Each aerosol species mass concentration frequency distribution scaled to estimated natural mass concentrations If current species mean is less than natural estimate, the that species is not scaled Geometric shape of species distributions is unchanged Current Natural Estimate Hanging bars Solid - current mean Dashed - natural estimate mean

Scaled aerosol extinction distributions Sipsey Alabama For SO4, NO3 and OMC use the current daily scattering efficiencies to calculate species extinction (scenario Nb) Joint aerosol extinction frequency distribution shape is altered from the current distribution Current Natural Estimate Hanging bars Solid - current mean Dashed - natural estimate mean

Aerosol bext and dv frequency distributions current and scenario Nb Sipsey Alabama Natural scenario joint distribution shape is derived from scaling current aerosol species mass concentrations to natural condition estimates Allows estimation of worst 20% dv or aerosol species extinction

Scenario N G90 dv All species adjusted to natural estimate east/west mean mass concentrations

Scenario N3 G90 dv All species except OMC adjusted to natural estimate east/west means OMC adjusted to 80% of current mean

Scenario N4 G90 dv All species except OMC adjusted to natural estimate east/west means OMC = current mean

Scenario N5 G90 dv All species except EC adjusted to natural estimate east/west means EC = current mean

Scenario N6 G90 dv All species except fine soil adjusted to natural estimate east/west means fine soil = current mean

Scenario N7 G90 dv All species except CM adjusted to natural estimate east/west mean CM = current mean

Scenario N8 G90 dv All species except fine soil and CM adjusted to natural estimate east/west mean Fine soil and CM = current mean

G90 dv change – increase OMC from natural estimate to 80% of current levels Sensitivity of G90 dv: scenario N to N3

Sensitivity of G90 dv: scenario N to N4 G90 dv change – increase OMC from natural estimate to current levels

Sensitivity of G90 dv: scenario N to N5 G90 dv change – increase EC from natural estimate to current levels

Sensitivity of G90 dv: scenario N to N6 G90 dv change – increase fine soil from natural estimate to current levels

Sensitivity of G90 dv: scenario N to N7 G90 dv change – increase CM from natural estimate to current levels

Sensitivity of G90 dv: scenario N to N8 G90 dv change – increase CM and Soil from natural estimates to current levels

5-yr baseline vs. long-term estimates scenario Nb Difference in worst 20% dv natural estimate SiteParamng90ng90ng90ng90  G90  G90%  nG90  nG90% ACAD1dv BADL1dv BAND1dv BIBE1dv BRCA1dv BRID1dv CANY1dv CHIR1dv DENA1dv GLAC1dv GRSA1dv GRSM1dv GUMO1dv MEVE1dv MORA1dv PEFO1dv PINN1dv REDW1dv SHEN1dv TONT1dv WEMI1dv YOSE1dv

Status/Next Steps Status: –The “N” approach (current baseline values scaled to Trijonis average natural species concentrations and using the new algorithm extinction without adjustments) is the most defensible of the approaches tried. –The use of current (or 80% of current) OMC as natural may be justifiable for many sites, but is beyond the committee’s purview and time frame. Next Steps: –Present material to larger audience –Document it for further dissemination and review

Appendix Maps of the difference between current species concentrations and natural levels.

aSO4: mass adjustment (Current – natural estimate) mean mass concentration difference

aNO3: mass adjustment (Current – natural estimate) mean mass concentration difference

OMC: mass adjustment (Current – natural estimate) mean mass concentration difference

EC: mass adjustment (Current – natural estimate) mean mass concentration difference

Soil: mass concentration adjustment (Current – natural estimate) mean mass concentration difference

CM: mass adjustment (Current – natural estimate) mean mass concentration difference

Sea Salt: mass adjustment (Current – natural estimate) mean mass concentration difference