1. Alaska Visibility Analysis
Ou Nopmongcol and Ralph Morris
RTOWG Update Call
6 August 2019

2. Ramboll Scope of work
Project Goal : Develop alternative glidepaths that account for international anthropogenic contributions
Two GEOS-Chem simulations performed by University of Alaska at Fairbanks
2016 Base Case
2016 Scenario with all anthropogenic emissions outside the U.S. set to zero (Zero Out Rest of World run; ZROW)
Conduct model performance evaluation
Develop alternative glidepaths using EPA’s SMAT/MATS software

3. IMPROVE sites
Denali
Trapper Creek
Kenai Peninsula Borough
Simeonof

4. GEOS-Chem 2016 Setup Version 12.1.0 2x2.5 degree resolution; 47 layers
Region
Inventory
Inventory Year US
NEI (monthly)
2011 scaled to 2013
Canada
APEI
2014
Asia
MIX
2010
Europe
EMEP
2012
Africa
DICE
2013
Global; rest of the world
CEDS (GEOS-Chem default)
Aircraft
AEIC
2005
Shipping
CEDS, EMEP
2014, 2012
Biomass
GFED4 (monthly)
2016
Volcanic SO2
Aerocom
2009 (degassing only)
Other Natural
(biogenic, lightning NOx, DMS, seasalt, halogen)
On-line
Meteorology-driven
Version
2x2.5 degree resolution; 47 layers
Out-of-the-box emission inventories
Output daily average concentrations
Other inventories that were turned on 'decaying plants', 'GEIA natural NH3', and 'global C2H6 from Tzompa-Sosa et al. 2017'

5. Uniform Rate of Progress (URP) Glidepath

6. ∆dv=10 ln [(bextnatural +bextint’ anthro)/bextnatural]
EPA’s Approach to address international Anthropogenic Source contributions
∆dv=10 ln [(bextnatural +bextint’ anthro)/bextnatural]
SMAT analysis calculates bextint’ anthro

7. SMAT (MATS) Analysis
Projection (typical): Use PGM modeling results for Base Year (BY, e.g., 2016) and Future Year (FY, e.g., 2028) to scale current years (CYs) IMPROVE PM2.5 concentrations through Relative Response Factors (RRFs)
RRF = PGM(FY) / PGM(BY)
PM2.5(FY) = IMPROVE_PM2.5(CY) x RRF
Separate RRFs for:
Most Impaired and Clearest Days
IMPROVE Site (Class I Area)
PM2.5 Species (SO4, NO3, EC, OMC, PMF and PMC)
Convert to deciview for developing Reasonable Progress Goals (RPGS) comparisons to URP Glide Path
Use IMPROVE visibility equation with extinction coefficients and f(RH) to convert concentrations (µg/m3) into light extinction (Mm-1)

8. SMAT : Projected ZROW RRF = PGM(ZROW) / PGM(BY)
PM2.5(ZROW) = IMPROVE_PM2.5{ } x RRF
Convert PM2.5(ZROW) to Bext PM2.5(ZROW)
Bextint’ anthro = Bext IMPROVE_PM2.5{ } - Bext PM2.5(ZROW)
∆dv 2064 =10 ln [(Bextnatural +Bextint’ anthro)/Bextnatural]
Step 1-3 done by SMAT