Natural background technical review committee - Meeting V

Natural background technical review committee - Meeting V

June 6, 2006

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.

Approach1. Scale current daily aerosol species mass concentrations

to Trijonis east/west means and form joint dv frequency distributions that estimate natural conditions • Assumes the respective aerosol species frequency distributions

have the same (geometric) shape under current and natural conditions. However, the shape of joint frequency distribution is altered for natural conditions.

• Only scale mass if current species mean is greater than the natural estimate for that component.

2. Apply SO4, NO3, and OMC scattering efficiencies derived from current range of mass concentrations• Assumes the range of SO4, NO3 and OMC particle mass

concentrations that occur under natural conditions undergo similar processing (e.g. have similar size distributions and hence scattering efficiencies) as the range of current species concentrations even though the natural mass concentrations may be significantly lower.

Sensitivity tests

Test the sensitivity of estimated natural condition worst 20% dv to changes in the aerosol species scattering efficiencies:

1. Scenario N – scattering efficiencies correspond to ‘scaled’ daily natural mass concentrations

2. Scenario Na – OMC scattering efficiencies correspond to ‘current’ daily mass concentrations

3. Scenario Nb – SO4, NO3 and OMC scattering efficiencies correspond to their respective ‘current’ mass concentrations

Consistency checks:

1. Compare estimates of worst 20% natural dv using long-term data records to establish species variability with variability derived from the 5-yr 2000 – 2004 baseline period.

2. Check that the best days' haze levels estimated for natural conditions are not greater than the best haze days for current conditions.

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 2000-2004

Natural Estimate

Hanging barsSolid - current meanDashed - 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 2000-2004

Natural Estimate


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

Worst 20% dv estimates: scenario N

• Use new IMPROVE algorithm scattering efficiencies corresponding to adjusted SO4, NO3 and OMC aerosol mass concentrations

Worst 20% dv estimates: scenario Na

• Use current OMC scattering efficiencies

Worst 20% dv estimates: scenario Nb

• Use current SO4, NO3 and OMC scattering efficiencies

G90 dv sensitivity for scenarios N, Na, Nb

• dv change from N to Na (adjust OMC efficiencies)

• dv change from N to Nb (adjust OMC, NO3 SO4 efficiencies)

• dv change from Na to Nb (adjust NO3 and SO4 efficiencies from Na)

Note: G90 = Worst 20%

G90 dv sensitivity to scenario N, Na, NbUrban sites included

• dv change from N to Na (adjust OMC efficiencies)

• dv change from N to Nb (adjust OMC, NO3 SO4 efficiencies)

• dv change from Na to Nb (adjust NO3 and SO4 efficiencies from Na)

Note: relaxed minimum data requirement to show 170 contoured sites

Best 20% dv estimates - Scenario N

• Use NIA scattering efficiencies on adjusted mass distributions

Best 20% dv estimates - Scenario Nb

• Use current SO4, NO3 and OMC scattering efficiencies on adjusted mass distributions

5-yr baseline vs. long-term estimatesscenario Nb

2000-2004 1988-2004

Difference in worst 20% dv natural estimate

Site Param n g90 ng90 n g90 ng90 G90 G90% nG90 nG90%

ACAD1 dv 568 23.1 12.8 1618 24.5 13.3 -1.3 5.7 -0.6 4.3

BADL1 dv 568 17.2 8.5 1668 17.6 8.2 0.4 2.6 0.2 -2.7

BAND1 dv 547 12.3 6.6 1581 12.7 6.3 0.4 3.1 0.3 -4.4

BIBE1 dv 527 17.5 7.5 1581 17.5 7.2 0.0 -0.2 0.3 -3.9

BRCA1 dv 519 11.8 7.3 1535 11.4 6.7 0.5 -4.0 0.6 -8.6

BRID1 dv 566 11.2 7.0 1618 10.9 6.9 0.3 -2.4 0.1 -1.0

CANY1 dv 533 11.3 6.8 1571 11.9 6.5 0.6 5.0 0.4 -5.1

CHIR1 dv 577 13.7 7.6 1607 13.5 7.0 0.2 -1.2 0.5 -7.1

DENA1 dv 549 10.0 7.4 1588 10.7 8.0 0.7 6.5 -0.6 7.8

GLAC1 dv 509 20.5 9.8 1630 20.1 9.2 0.4 -2.1 0.5 -5.6

GRSA1 dv 558 13.0 7.0 1659 12.3 6.6 0.6 -4.9 0.5 -6.8

GRSM1 dv 566 30.2 12.2 1554 31.4 12.5 1.2 4.1 -0.3 2.3

GUMO1 dv 512 17.3 7.0 1535 16.2 6.6 1.1 -6.6 0.4 -5.7

MEVE1 dv 528 13.3 7.5 1571 12.1 6.7 1.2 -9.0 0.8 -10.3

MORA1 dv 552 18.3 9.2 1585 20.4 9.5 2.1 11.5 -0.3 3.5

PEFO1 dv 513 13.7 7.0 1507 13.1 6.4 0.6 -4.4 0.6 -8.4

PINN1 dv 524 18.6 8.4 1575 19.7 8.7 1.1 6.1 -0.3 3.8

REDW1 dv 525 18.6 14.2 1595 19.9 14.5 1.3 6.8 -0.3 2.3

SHEN1 dv 537 29.6 12.2 1525 30.7 12.3 1.1 3.8 -0.1 1.1

TONT1 dv 535 14.5 7.0 1512 14.6 6.7 0.1 0.7 0.2 -3.5

WEMI1 dv 543 10.5 6.5 1585 10.7 6.4 0.2 2.3 0.1 -2.0

YOSE1 dv 521 18.0 8.6 1575 17.8 8.2 0.2 -1.3 0.4 -4.4

Glide Slopes

1. 2000-2004 worst 20% dv baseline: old and new IMPROVE algorithms

2. Worst 20% dv natural estimates: compare new approach (scenario Nb) to original default values

3. Worst 20% dv baseline to estimated natural condition glide slopes in dv/10yrs

4. Change in worst 20% dv glide slopes: new approach – default approach

5. Examples of aerosol species glide slopes

Note – glide slopes calculated from 5-yr baseline (mean of 3-5 annual G90 values) to natural G90 estimator (n>250 FD)

G90 dv 2000-2004 baseline

Old IMPROVE algorithm (OIA)

New IMPROVE algorithm (NIA)

G90 dv natural condition estimates

Old ‘default approach’ using OIA

‘New approach’ using NIA(same as slide 10)

Glide slopes for G90 dv natural estimates

New approach with NIA

Old ‘default’ approach with OIA

Change in glide slope: new approach vs. old default approach

• Values shown are (new – old) in dv/10yr for worst 20% dv natural estimates• Positive values indicate higher magnitude (steeper glide slope) for new approach

Aerosol species glide slopes

Ammonium nitrate extinction

Ammonium sulfate extinction


Light absorbing carbon extinction

Particulate organic matter extinction

Fine soil extinction

Coarse mass extinction


Summary

1. All light extinction components are scaled to estimated natural condition mean mass concentrations in a consistent manner.

2. Using current SO4, NO3 and OMC scattering efficiencies increases natural condition worst 20% dv estimates by 0 to 1 dv among non-urban IMPROVE sites.

• We recognize that applying current particle scattering efficiencies to estimated natural aerosol mass concentrations may have conceptual flaws. For example, natural haze estimates will be elevated in regions where current levels of anthropogenic pollutants are high, producing a spatial trend that is not likely representative of natural conditions. However, we chose this approach in order to maintain consistency with the application of aerosol species scattering efficiencies in the new IMPROVE algorithm to current aerosol data.

3. Worst 20% dv estimated using 2000-2004 baseline data agree to within less than 1 dv natural condition estimates derived from long-term (~15 yrs) data.

4. In no cases are estimated natural worst 20% dv greater than current conditions.

The new approach allows calculation of species extinction on the worst 20% natural condition visibility days. This in turn allows us to estimate species specific glide slopes for RHR planning.

Appendix

Scenarios to test the effect of scaling only aerosol species mass concentrations for components with predominantly anthropogenic sources:

1. N1 – only scale SO4 and NO3 to estimated natural mass concentrations

2. N2 – only scale SO4, NO3 and EC to estimated natural mass concentrations

•Aerosol light extinction frequency distributions at SIPS1 for scenario N

Worst 20% dv - Scenario N1

• Control SO4, NO3 and EC

Worst 20% dv - Scenario N2

• Control SO4 and NO3

Scaled aerosol extinction frequency distributions

• Sipsey Alabama • use adjusted daily

scattering efficiencies to calculate species extinction in scenario N

• Max SO4 bsp is 8.2 Mm-1, max OMC bsp is 35.5 from scenario N

• Max SO4 bsp is 12.5 Mm-1, max OMC bsp is 50.6 from scenario Nb

Current 2000-2004

Natural Estimate


Documents

Natural background technical review committee - Meeting V