WRAP Regional Modeling Center - Simulation Specifications 

Scenario Name: 2018 Preliminary Reasonable Progress Simulation version B 

RMC Code: “PRP18b” 

Date Specifications Prepared: 4/29/2009, revised August 11, 2009

Time Window for Modeling/Analysis: 

• Emissions modeling April 27 to May 15, 2009 

• Air quality modeling May 15 to June 15, 2009 

• Analysis results June 24, 2009 

• All PRP18b files to TSS July 2009 

Description: 2018 Annual 36-km CMAQ air quality model simulation using PRP18b future year emissions, 

consisting of selected updates from PRP18a. 

Purpose/Objective: Evaluate the regional haze air quality for future year 2018 conditions with all known and 

expected controls on land-based emissions sources as of March 2009. Provide predicted 2018 future year air 

quality and visibility conditions in the Western Class I areas for regional haze plans.

Expected Analysis Methods: Specific analysis methods will generally be determined based on the nature of 

the simulation and the stated purpose and objectives. These typically involve a number of standard postprocessing products used to elucidate relevant modeling results and analyses and aid in summarizing and 

interpreting the simulation results. For the present simulation these would include: 

• Standard displays of spatial distribution of concentrations of relevant pollutants (Sulfate, Nitrate, PM, 

OC, EC, etc..) for various temporal periods (daily, monthly, seasonal and annual totals) 

• Spatial plots of differences between 2002 Plan Version D and PRP18b, as well as between PRP18a and 

PRP18b model predictions 

• Stacked-bar charts of contributions to light extinction for the 20% best and 20% worst days at each 

IMPROVE site 

• Output files of SMOKE emissions and CMAQ air quality results to TSS 

• SMOKE reports processed and uploaded to TSS 

Input Data: 

Emissions – emission data and QA found at: http://newpah.cert.ucr.edu/aqm/308/qa_prp18b36.shtml 

The following 2009 updates for PRP18b include: 

• Update of California 2018 on-road and non-road emission inventories PDF 

• Update of 2018 locomotive emissions PDF 

• Update of WRAP 2018 stationary point source emissions PDF

• Update of WRAP 2018 area source emissions PDF

• Mexico 2018 projections PDF
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The following emissions data did not change from previous simulations:

• From Base02a 

o BEIS3 biogenic emissions (includes soil NO) 

o Windblown fugitive PM dust emissions – all components from WRAP WB Dust model 

o WRAP NH3 from WRAP NH3 model 

o Ontario, Canada point fires 

• From Plan02a 

o WRAP baseline wildfires 

o WRAP baseline wildland fire use 

o Offshore commercial shipping: no change (see Plan02a) The effect of changing the Eastern 

Pacific emissions to 2018 projections will be analyzed in the PRP18cmv sensitivity modeling 

scenario 

• From Base18a: 

o WRAP (except California) non-road mobile (annual and seasonal) 

• From Base18b: 

o CENRAP on-road mobile 

o WRAP baseline prescribed fires (natural and anthropogenic) 

o WRAP baseline agricultural fires 

o WRAP baseline non-federal rangeland fires 

• From PRP18a: 

o Non-WRAP stationary area 

o Non-WRAP stationary point 

o Non-WRAP mobile sources (on-road & off-road) 

o WRAP Oil & Gas 

o Fugitive dust 

o CENRAP & VISTAS point fires 

o Offshore Area, Gulf of Mexico 

o Gridded Offshore Shipping (Gulf of Mexico and Atlantic: Corbet/ENVIRON inventory) 

o Canada - 2020 inventory 

o Mexico – Road dust extracted from Phase II area inventory and had transport factors applied. 

The following emission updates were included in simulation PRP18b:

• Stationary Area 

o WRAP: Updated 2018 inventory 

o Mexico: Phase III inventory and updates to gridding data 

• Non-road Mobile 

o WRAP: Updated 2018 inventory for California 

o Mexico: Phase III inventory and updates to gridding data (annual) 

• On-road Mobile 

o WRAP: Updated 2018 inventory for California 

o Mexico: Phase III inventory and updates to gridding data 

• Fugitive Dust 

o WRAP: Extracted from Updated 2018 stationary area source inventory 

o Mexico: Extracted from Phase III inventory 

• Stationary Point 

o WRAP: Updated 2018 inventory 

o VISTAS: Updated 2018 Best & Final inventory 
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o Mexico: Phase III inventory 

• Documentation on input data, model settings, and modeling/QA procedures provided through standard 

reporting products: PRP18b_Inventory_summary_v{mmddyy}.xls

o Simulation schedule and input files 

o Summary of inventory inputs to the simulation with descriptions of the changes to each input 

Other Inputs and Model Settings

• Initial and Boundary Conditions based on natural GEOS-CHEM simulation 

• Model version, settings and configuration same as for 2002 Plan B 

• Time period simulated – annual, typical year, meteorology for 2002 used 

Results: 

Summary tables and maps

Table 1. PRP18b annual emissions summary by regions (tons/yr) 

Region CO NOX VOC NH3 SO2 PM10 PM2_5 PMC 

US 90741069 12745979 66309558 5368193 7845370 15989089 5029158 11015336

WRAP 23948636 2873849 22257586 943731 683989 4981494 1620019 3392036

CENRAP 20167299 3713812 16034674 2423559 2232321 7157076 1783387 3551486

VISTAS 23246332 2828046 18784889 792822 2165368 2309828 917211 1325749

MWRPO 11298046 1704809 4716975 789173 1794155 664226 343924 201263

MANE-VU 11917915 1285561 4402945 418907 925065 871886 360126 493440

Canada 12346108 2175237 21050573 428767 2173766 3475854 887462 2588666

Mexico 9793174 2209114 15252537 814815 3244297 1337612 751393 590409

Pacific 

Shipping 40868 524797 367468 149 280561 36352 35220 1132

Atlantic/Gulf 

Shipping 30158 571769 12587 108 229651 63726 62756 971

Total 203529605 30632973 169189793 11980224 21574544 36887143 11790656 23160487

Table 2. PRP18b WRAP total annual emissions by sector (tons/yr) 

Sector CO NOX VOC NH3 SO2 PM10 PM2_5 PMC 

Fires 8928013 202217 436714 45263 53856 726518 627618 119796

Area 1386853 290874 1830236 25387 108274 233469 205202 28306

Point 714163 811324 300509 11564 512467 196677 59046 147229

Non Road 4520104 557423 332659 922 3186 35095 31673 3442

Onroad 5706430 533287 410149 43339 6116 38603 25509 13094

Biogenic 2624814 286996 18197340 0 0 0 0 0

WOG 68260 191728 749979 0 89 0 0 0

Road Dust 0 0 0 0 0 689599 72821 616779

Fugitive Dust 0 0 0 0 0 1099367 166474 932901

Wind-Blown 

Dust 0 0 0 0 0 1962165 431676 1530489

Offshore 

Platforms 0 0 0 0 0 0 0 0

Offshore 

Shipping 40868 524797 367468 149 280561 36352 35220 1132

Ag Ammonia 0 0 0 817256 0 0 0 0

Total 23989504 3398646 22625055 943880 964550 5017846 1655240 3393168
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Discussion: 

Emissions Summary

The objective of emissions simulation PRP18b was to incorporate emissions inventory updates completed 

during 2009 by WRAP contractors to create a new future year, annual 36-km grid resolution emissions dataset 

for air quality modeling. As summarized in the Input Data/Emissions section of this specification sheet, we 

received updated 2018 PRP inventories (for selected source categories – see above) for the WRAP states. We 

also obtained updated 2018 inventories for the VISTAS states, year 2020 inventories for Canada and new 2018 

national inventories for Mexico (Phase III). We combined these updated inventory data with existing emissions 

data from the PRP18a emissions scenario to develop the PRP18b emissions. We will summarize simulation 

PRP18b by RPO, Canada, and Mexico in terms of new inventories, emissions data and modeling corrections, 

and emissions that we reused from previous simulations. Tables 1 and 2 summarize the annual emissions totals 

for simulation PRP18b for the different regions of the modeling domain and for the different inventory sectors 

within the WRAP region, respectively. This section will conclude with a discussion of the overall impacts of 

these changes on the emissions modeling results. 

The RMC received new data for the WRAP states and tribes that included 2018 PRP inventories for the 

stationary area, stationary point, on-road mobile, and non-road mobile sectors. We extracted fugitive dust PM 

emissions sources from the stationary area inventory using the list of sources consistent with simulation PRP18a 

(originally developed during Base18b modeling). The changes to the WRAP stationary area inventory impacted 

only some of the states in the region. The states impacted by this inventory update included California, Idaho, 

Nevada, South Dakota, and Washington. The WRAP stationary point inventory update impacted all 13 states 

and some of the Tribes. The on-road mobile updates only impacted California and the non-road mobile updates 

impacted all of the states in the WRAP region. The rest of the inventory sectors in the WRAP region remained 

unchanged in simulation PRP18b relative to PRP18a. We also updated the emissions data for the VISTAS RPO 

in simulation PRP18b. 

We incorporated an updated 2018 stationary point inventory for the VISTAS states in simulation PRP18b. We 

used the 2018 best & final inventory from the VISTAS RPO as a replacement to the 2018 point inventory that 

we used in simulation PRP18a. We did not make changes to any of the other U.S. inventories outside of the 

WRAP and VISTAS regions in simulation PRP18b. In addition to the WRAP and VISTAS updates, we 

included new 2018 Mexican inventories in simulation PRP18b. 

We updated the Mexico inventories in simulation PRP18b with the Phase III 2018 inventory produced by ERG, 

Inc. The Phase III 2018 Mexico inventory replaced the 1999 Mexican inventories that we used in simulation 

PRP18a. The Phase III inventories cover the entire country for all emissions sectors. We worked with ERG, Inc. 

to reconcile state/county coding changes in the 2018 Phase III inventory with the spatial surrogates that we 

developed for Mexico during the PRP18a modeling. Instead of including new municipalities in the 2018 Phase 

III inventory, ERG added the emissions for these new areas back into the municipalities used in the Phase III 

1999 inventory. We prepared the fugitive dust inventories from Mexico through the application of revised 

PM10/PM2.5 ratios and vegetative scavenging reduction factors in a manner consistent with the U.S. inventories. 

As the 2018 Phase III Mexican inventory did not contain road dust estimates, we used the same Mexican road 

dust inventory that we used in all previous modeling runs. The inventory sources for Canada, as well as the 

domain-wide biogenic emissions did not change in simulation PRP18b. 

Overall the WRAP emissions on an annual basis (annual totals for all WRAP states) decreased for all inventory 

pollutants, with the exception of CO, for simulation PRP18b relative to simulation PRP18a. The largest 

reductions for the PM pollutants came from the non-road mobile and fugitive dust/stationary area sectors. 

Increases in PM emissions from the on-road mobile and stationary point sectors slightly offset the PM 
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emissions reductions in PRP18b. The NOx emissions reductions in simulation PRP18b relative to PRP18a were 

driven by the stationary point sector, with smaller reductions from non-road mobile and stationary area. The 

only sector that exhibited NOx increases in comparing these two simulations was the on-road mobile sector. The 

SO2 reductions in simulation PRP18b relative to PRP18a were driven primarily by the stationary point sector 

with smaller reductions in the stationary area and non-road mobile sectors. There was a small offsetting 

increase in SO2 emissions from the on-road mobile sector. Simulation PRP18b included only reductions in NH3

emissions relative to simulation PRP18a and these were the result of changes primarily in the on-road mobile 

sector. Smaller NH3 reductions occurred in the stationary point, non-road mobile, and stationary area sectors. 

The stationary area sector contributed the only VOC reduction, which was offset by smaller increases in VOC 

emissions from the on-road mobile, non-road mobile, and stationary point sectors. A relatively large increase in 

CO emissions from non-road mobile sources was offset by smaller decreases in the stationary area, stationary 

point, and on-road mobile sectors. 

Relative to simulation Plan02d, the PRP18b WRAP emissions decreased for PM2.5, NOx, SO2, NH3 and CO and 

increased for PMC, PM10, and VOC. The PM2.5 reductions were driven by the on-road mobile, non-road mobile, 

and stationary point sectors and offset by increases in the stationary area, road dust and fugitive dust sectors. 

The largest increase in PM2.5 is from the fugitive dust sector and reflects the expanded list of dust sources that 

we applied after simulation Plan02d. The NOx emissions decreased as a result of the on-road mobile, non-road 

mobile, and stationary point sectors. These decreases were offset slightly by NOx increases in the stationary area 

and oil and gas sectors. The SO2 reductions were driven by stationary point, on-road mobile, and non-road 

mobile sectors. A large CO reduction in the on-road mobile sector was offset by increases in the stationary area, 

stationary point, non-road mobile, and oil and gas sectors. PMC and PM10 increased in simulation PRP18b 

relative to Plan02d primarily because of the fugitive dust and road dust sectors. The only major offset to these 

increases were reductions in PMC and PM10 emissions from non-road mobile sources. Decreases in NH3

emissions were driven by the on-road mobile sector. Large increases in VOC emissions from the oil and gas and 

stationary area sectors were offset by smaller decreases in the on-road and non-road mobile sectors. 

Visibility Modeling Results 

The objective of the PRP18b simulation was to evaluate the regional haze air quality for future year 2018 

conditions with all known and expected controls as of March 2007 and to provide predicted 2018 future year 

air quality and visibility conditions in the Western Class I areas for December 2007 regional haze plans. The 

PRP18b case includes new updates to the emissions completed after the PRP18a simulation, as described above. 

The PRP18b case is designed to be compared to the 2002 Plan Case Version D (Plan02d) to evaluate changes in 

model simulated visibility from 2002 to 2018. The PRP18b case will also be compared to the PRP18cmv 

simulation.

Relevant Output Products 

Analysis products for the comparison of the PRP18b simulation to the Plan02d simulation can be found at: 

http://pah.cert.ucr.edu/aqm/308/cmaq.shtml#prp18bvsplan02d

• Relevant model output products include daily and monthly spatial distributions of Regional Haze 

contributing pollutants; 

• Model output concentrations will serve as indication of future year 2018 baseline visibility conditions; 

• Results of this simulation have been compared with and 2002 Planning (Plan02d) simulation to evaluate 

changes in model simulated visibility using both spatial plots of the differences between the two 

simulations for each PM species;, and 

• On the WRAP TSS, the Visibility Projections tool displays the model-based projected 2018 visibility 

results using Relative Response Factors from IMPROVE monitoring data. To use this tool, 1) Click the 
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TSS link above, 2) Select a site(s), 3) Click the "Modeling" button below the map, and 4) Select the 

"Visibility Projections" link. 

Summary of Key Findings

To evaluate seasonal differences in the comparison of PRP18b to Plan02d, we prepared plots of monthly 

average changes in concentrations for ozone and each of the PM species. Plots for all 12 months are available 

on the RMC webpage (see: http://pah.cert.ucr.edu/aqm/308/cmaq.shtml#prp18bvsplan02d) but we present 

summary results here for the months of January and July. These months were selected because the largest 

variation in model results is typically between the winter and summer months. Figures 1 through 4 show the 

monthly average model concentrations of the PM species for the PRP18b case relative to the Plan02d case. 

Figure 1 (top) shows the changes in sulfate for January and July. The largest change was caused by updates to 

the Mexican SOx emissions inventory, with large reductions in sulfate in the Baja California area and large 

increases in sulfate in northern Mexico and southern Texas. Overall, there was a mixed response in sulfate 

concentration in the WRAP states in January, and there was a reduction in sulfate in the WRAP states in July. 

The annual average change in sulfate in Figure 5 shows that there was a reduction in sulfate in the PRP18b 

simulation compared to Plan02d. 

Figure 1 (bottom) shows the change in nitrate for January and July. There were reductions in nitrate in most of 

the WRAP region throughout the year, due largely to large reductions in NOx emissions in the PRP18b mobile 

source inventory. The PRP18b point inventory had reductions in NOx emissions in some areas and increases in 

other areas, and Figure 2 shows small increases for PRP18b compared to Plan02d nitrate in parts of Nevada and 

Arizona in January. The reductions in nitrate in PRP18b were largest in the winter months because nitrate 

concentrations are much larger in the winter than in the summer months. 

 Figure 2 (top) shows that there were mostly reductions in ammonium concentration in PRP18b compared to 

Plan02d, consistent with the large reductions in nitrate. There were some areas, mostly in Mexico and Texas, 

where ammonium increased in PRP18b because of the increases in sulfate in PROP18b compared to Plan02d. 

Figure 2 (bottom) shows the change in ozone in PRP18b compared to Plan02d for January and July. During 

January, PRP18b had higher ozone concentration in urban influenced areas because of the reduced NOx 

emissions in PRP18b. During winter months, high NOx concentrations mostly acts to titrate ozone, so 

reductions in NOx cause increases in ozone in winter months. However, the ozone concentrations are usually 

low during the winter and exceedences of the ozone NAAQS are rare. During July, the PRP18b NOx 

reductions cause significant reductions of ozone in the WRAP region with the largest reductions, up to 8 ppb for 

the monthly average, occurring in California’s central valley. 

Figure 3 (top) shows the change in elemental carbon (EC) in PRP18b compared to Plan02d for January and 

July. EC concentrations were reduced in the WRAP region throughout the year in PRP18b, in part due to 

reductions in mobile source emissions. Reductions were larger in the winter months, as much a 2 ug/m3 in 

December compared with smaller reductions of up to 1 ug/m3 in July, because of less vertical mixing in the 

winter months. Figure 3 (bottom) shows changes in organic carbon (OC) in PRP18b compared to Plan02d for 

January and July. There were mostly reductions in OC in PRP18b compared to Plan02d, with the exception of 

increases in OC in both the Seattle and Phoenix areas in PRP18b. 

 

Figure 4 (top) shows the change in total PM2.5 in PRP18b compared to Plan02d for January and July. PM2.5 

represents the sum of the changes in the speciated PM results shown in Figure 1 through 3. The largest 

reductions in PM2.5 were in January in California, as large as 6 ug/m3

, because of large reductions there in 

nitrate, ammonium and EC from the updated mobile source inventory in PRP18b. The magnitude of the 

reductions in PM2.5 for PRP18b were smaller in the summer months in California, but reduction extended over 
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a much larger area, including the mountain states, because of reductions in sulfate, ammonium and EC in those 

areas for the PRP18b simulation. 

Figure 4 (bottom) shows the change in total coarse matter (CM) in PRP18b compared to Plan02d for January 

and July. There were mostly increases in CM associated with urban areas in PRP18b, with the exception of 

Clark County, NV, were there were large reductions in CM. 
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Figure 1. Top panels shows change in monthly average sulfate concentration for the PRP18b compared to the 

Plan02d CMAQ simulations for January (left) and July (right). Bottom panels show change nitrate for the same 

periods. 
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Figure 2. Top panels shows change in monthly average ammonium (NH4) concentration for the PRP18b 

compared to the Plan02d CMAQ simulations for January (left) and July (right). Bottom panels show change in 

ozone for the same periods. 
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Figure 3. Top panels shows change in monthly average elemental carbon (EC) concentration for the PRP18b 

compared to the Plan02d CMAQ simulations for January (left) and July (right). Bottom panels show change in 

organic carbon aerosols. 
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Figure 4. Top panels shows change in monthly average total PM2.5 concentration for the PRP18b compared to 

the Plan02d CMAQ simulations for January (left) and July (right). Bottom panels show change in coarse matter.