Development, Maintenance andEvaluation of CALPUFFPresented at:9thConference on Air Quality ModelingOctober 9-10, 2008by:Joseph ScireTRC Environmental CorporationModel DevelopmentModel Development• CALPUFF system undergoes continual refinementand development, with new features and productivityenhancements. EPA provides no funding fordevelopment or maintenance activities.• TRC has developed graphical interfaces andvisualization tools which are distributed to the publicwithout cost• Technical developments are made within TRC bothwith and without external funding• EPRI PRIME downwash module• Flexible coordinate transformations• MMS updates for coastal applications• VISTAS enhancements• Forest Service enhancements• NASA and Forest Service sub-hourly Version 6Model Development• Technical developments are also contributed fromother users and researchers• Hybrid puff-particle version - Switzerland• Large-particle settling (volcanic ash) - Italy• Solar radiation effects oncanyon sidewalls and terrainshadowing - Italy• TRC has implemented procedures to satisfy currentregulatory needs without federal funding anddistributes these codes to the public for free including:• EPA BART 98thpercentile computations• Proposed 2008 FLM (FLAG) visibility method• Processors are continuously updated to accept new orrevised data formats• TRC has develop interfaces to mesoscale prognosticmeteorological models such as MM5, WRF, RUC,RAMS and Eta and distributes these codes to thepublic for free.Model Development• Graphical User Interfaces (GUIs)–CALPRO• Geophysical processors (TERREL, CTGCOMP, CTGPROC,MAKEGEO)• Surface meteorological data processor (SMERGE)• Upper air data processor (READ62)• Precipitation processors (PXTRACT, PMERGE)–COORDS• Converts to/from any of the following Geodetic, UTM, Lambert ConicConformal, Tangential Transverse Mercator, Polar Stereographic,Equatorial Mercator, Lambert Azimuthal Equal Area• Datums (~150 different datums available worldwide, including WGS-84,NAD-27, NAD-83)–BUOY• Processes buoy data and creates SEA.DAT files–UAMAKE• Extracts data from a prognostic (e.g., MM5) file to create soundings asreplacements for missing upper air dataModel Development• Graphical User Interfaces (GUIs)–PRTMET• Produces vector plots, contourplots of meteorological fields• Time series files for plotting• Uses Surfer plotting package (Golden Software package)–CALVIEW• Displays vector/contour/3-D perspective plots• Animations–CALWindRose• Wind rose plotting software• Displays wind roses directly fromSURF.DAT, UP.DAT, CALMET.DATor 3D.DAT files–SurfSizer• Utility working with Surfer to quickly re-size plots–SurfExporter• Utility working with Surfer to quickly export plots in various formats(BMP, JPG, TIF, etc.) and user-specified resolutionModel Development• Graphical User Interfaces (GUIs)–SIA Generator• Develops a radius of concentration values above a threshold• Useful for determining the Significant Impact Area (SIA)–PICtoReport• Imports image files into PowerPoint or Word• Automatic sizing and centering of each image• Works with PNG, BMP, JPG, TIF, GIF and BLN files–CALPUFF Plot (currently in testing phase)• Generates KML files from BPIP input files• Enables 3D viewing of building layout in Google Earth• Useful for QA and display purposes•New:Ability to overlay concentration isopleths on base mapSample of CALPRO Google EarthInterfaceModel Development• Graphical User Interfaces (GUIs)–FEPS2BAEM• Fire Emission Production Simulator (FEPS) is a Forest Service modelthat predicts fuel consumptionand emissions from wildfires andcontrolled burns• FEPS2BAEM convertsFEPS output data tothe CALPUFF buoyantarea source emissions file format (BAEMARB.DAT)–ScavCoeff• Estimates size-dependent wet scavenging coefficients for liquid andfrozen precipitation• For particulate matter < 20μm diameter–AER2CAL• Converts AERMOD output concentration files into CALPUFF formattedconcentrations files• Allows use of CALPUFF postprocessing tools with AERMOD output• Contour plots, animations, base maps, etc.Model Development• Additional processor options and datasets– Terrain data options include 30arcsec (900m), 3 arcsec (90 m), 1 arcsec(30m) USGS DEMs, SRTM dataformat, generic data formats– Landuse – new option to process NLCD format• Repartitioning of HNO3/NO3(POSTUTIL)– Source contribution analysis– Streamlined one-step ALM processing– Non-linear chemistry effects (NO3)– Computation of total S and N deposition•No-Observations version of CALMET– Uses gridded 3-D data fields as initial guess fields– Adjusts winds for fine-scaleterrain effects on CALMET grid– Allows forecast applicationsModel Development - CALMET•New interface programs– WRF– NCEP models: ETA and RUC2– RAMS– MM5 (Version 3)– enhanced output (3D.DAT, 2D.DAT files)•SEA.DAT filescreated from MM5 model usinghigh resolution sea-surfacetemperature data•COARE Algorithms•Convective mixing over water– Maul-Carson (M-C) scheme and Batchvarova-Gryning (B-G) scheme(1994)Model Development - CALPUFF• Boundary condition module• Rain hat option on stacks• Mass balance/flux tracking options• Horizontal puff splitting• NH3as an active species• New turbulence profile option using AERMOD profile– Original CALPUFF turbulence parameterization– AERMOD turbulence profiles• AERMOD met data options– Option in CALPUFF to read AERMOD met data files– Utility to create AERMOD met files from 3-D CALMET outputModel Development - CALPUFF• Time Step < 1 Hour (CALMET, CALPUFF)• Secondary organic aerosol module• Terrain enhancement of precipitation• Fogging and icing (cooling towers)– Visible plume lengths– Frequency of plume-induced fogging and icing• Turbulence advection• Platform downwash• Back trajectory analysisModel Development – On-going• Nested grid option• Option to name receptor setsand process by receptor group• Meteorological evaluation software (METSERIES andMETCOMP)– Wind rose (graphics completed)– Time series plots– Scatter plots– Statistics– X-Z cross sections– Standard report• Enhanced animation options– Create, name and save animation files for future playing (completed)– Display of puff movements and growth (on-going)Model MaintenanceModel Maintenance• With few exceptions, all model maintenance is donewithout contractual funding support• Investigate all reported issues. Request detailederror reports and test datasets from user• About 75% found to be due to data problems,hardware problems or input errors• Bugs are isolated and fixed with detailed updates toin-code documentation and version/level journaling• Model Change Bulletin (MCB) updated• Updated code(s) run in EPA CALPUFF Update Tooland results sent to EPAModel MaintenanceCALPUFF MCB HistoryNo ActionFebruary 14, 2008MCB-ENo ActionJune 27, 2008MCB-E (Part 2)June 29, 2007AcceptedDecember 16, 2005May 1, 2007June 23, 2007MCB-BMCB-C – VISTASMCB-DJune, 2006AcceptedJuly 16, 2004MCB-AApril 15, 2003FR NoticeOfficial VersionEPA ActionCALPUFFNote: MCB-C contains all fixes in VISTAS version released August 4, 2006Model Maintenance – The Plan• TRC– provides developmental model version as amechanism for quickly evaluating bug-fixes andmodel enhancements• EPA action at periodic intervals– reviews bug fixes and considers new options andfeatures• accept/recommend new features• suggest changes/modifications• Accepted features placed in regulatory recommendedoption set• Other features may be retained for additional testing,or abandoned or not recommendedfor regulatory useModel Maintenance - Reality• Problems with Review Process– Long delay in EPA reviewing bug fixes– EPA review of model enhancements on hold• Example Enhancement– Surface station data assigned to grid cells usingnearest-station in EPA-approved CALMET– Surface station data interpolated to grid cells using1/R2weights in VISTAS CALMET– Nearest-station technique leads to sharp gradients– EPA criticizes sharp gradients yet has notconsidered this enhancement which was in theVISTAS code and removed at EPA’s insistence inthe current EPA-approved codeModel Maintenance• Earth Tech/TRC commitments have beenscrupulously adhered to:– Model maintenance continues to be done by TRCwithout EPA support– Agreement to keep regulatory model unchangedon web site– EPA determines “EPA-approved” version• What has happened to process?– Changes at EPA in management and staff– EPA Modeling Group – some loss of institutionalmemory and continuity?Model Maintenance• EPA presentations at 2007 and 2008 R/S/L ModelersWorkshops contain misleading statements aboutCALPUFF, and include examples that do not reflectgood modeling practice• CALPUFF Regulatory Update (June 2008 R/S/LWorkshop)– “Lack of adequate documentation”• “New MREG option in CALMET not well-documented”• “User’s guide last updated in 2000”• “Many important technical details are not documented,except in code”– “serious unresolved technical concerns”Model Maintenance• Documentation?– 885 pages of detailed technical documentation and userguide updates in March 2006 describing MMS changes– 853 pages of documentation in original user guides– Compares well in technical detail and content with AERMODdocumentation• Why should this be known to EPA? MMS projectchanges were the subject of the EPA oversight:– EPA represented on Scientific Review Board for MMSproject (John Irwin, Modeling Group, OAQPS)– MMS presentation was made at June 2007 EPA R/S/LModelers Workshop. Updated User’s Guides availableonline since early 2006 (listed in presentation)– Multiple references made toMMS reports by TRC to EPAduring VISTAS model reviewModel Maintenance• Constructive criticism and helpful suggestions arealways welcome, but vague references to problemswithout backup and data are not helpful orconstructive.• CALMET MREG Option?– Option formulated by TRC with EPA review– Input file language presents option choices• Unresolved Technical Concerns?– Issue was default value for new CALMET inputvariable. Value resolved to EPA satisfaction (May2007)Model MaintenanceVISTAS CALMET technical enhancements inv5.8 awaiting EPA review• Fully interpolated 2D fields for surface-layertemperature and density instead of nearest-stationselection of surface meteorological data• Use consistent surface-layer stability correctionprofiles throughout• Recognize convective over-water boundary layer(instead of using neutral boundary layer formulationsfrom OCD)• Use Coupled Ocean Atmosphere ResponseExperiment (COARE) bulk flux model for overwaterfluxes in place of older OCD methods• Updated convective boundary layer parameterizationfollowing Batchvarova and GryningModel Maintenance• EPA CALPUFF studies used in EPA presentationshave not been open review by TRC or the public• Important for transparency that all modeling files onwhich decisions/memos are based are madepromptly public– Results presented in public forums rather thancommunicated directly– Modeling and data files not available– Lack of constructive criticism with a focus onresolving issuesWind Field Bull’s EyeFrom Bret Anderson (USEPA Region 7)’s presentation at the 2007 Regional StateLocal Modelers Workshop“Illustration of meteorological issues– CALMET diagnostic meteorological model”,When MM5 does not match theobservations• Bull’s eye features is a result of MM5 winds notmatching observations. Issue may be withMM5 or a non-representative observation• Solution:– (1) Pure NOOBS mode : MM5 only fields– (2) Pure observation mode– (3) Hybrid mode with MM5 as initial guess field,small R1-R2, matching the observations right at thestations and MM5 fields away from them– (4) Hybrid mode with poorly selected large R1/R2,creating a bull’s eye, with station winds clashing withMM5 fieldsSo 3 good ways to run CALMET without creating a sharpdiscontinuity and 1 bad way, creating a bulls’ eye• Sydney Harbor – Summer sea breeze• Local observation at odds with mesoscalefeatures• MM5 at 1.33 km resolution• 5 surface stations, 1 buoy, 1 upper air station(not used in hybrid)• Plots: 40km x 30km ; resolution: 1kmHow to run CALMET when MM5does not match the observationsSolution 1: Run in NOOBSSolution 2: run in OBS-onlySolution 3 : Hybrid with R1<<RMAX1R1=1km – RMAX1=20km4. EPA’s bull’s eye no-solution: hybrid withR1>>RMAX1R1=20km – RMAX1=3kmAERMOD• And what would AERMOD do in this region?• An infinite radius bull’s eye, only matching one station and notrepresenting observations at any other sites....Solution for Better EPA andCommunity Input?Establish Science Advisory Committee• TRC-organized CALPUFF technical committee• Provide objective, unbiased advice• Identify model improvements• Possible Members:– EPA– FLMs– MMS– PBL Expert– Dispersion Modeling Expert– 2-3 Active Users (Consultants or Industry)– One public meeting per year via web-link• New web-based user group (or promote existing e-list atWashington (Clint Bowman))Model Applicability andEvaluationModel Applicability – Near-Field:AERMOD vs. CALPUFFOverwater turbulencemodule and TIBLalgorithm to treat coastal fumigationNo coastal TIBL or fumigationalgorithmCoastal effects, fumigationCALPUFF retains previous hoursemissions within domain and evaluatesimpacts from themNot treated. AERMOD has nomemory of pollutants emittedduring previous hoursMass accumulation duringstagnation. Memory?Calm winds treatedNot treated – removed from theanalysisCalm windsFull variability considered whenCALMET meteorological dataset usedNone. Single station wind isapplied over entire modelingdomainHorizontal wind variabilityCALPUFF determines surfaceconditions in each grid cell and appliesit to a puff as it passes that cell.Downwindconditions of each andevery source are evaluated on a puffby-puff basisAERMOD looks upwindofmet.stationin a radius of 1-km tocharacterize turbulence up to 50-km downwindofsourcePolicy on treating surfacevariabilityFull variability – uses 2-D gridLand use variability allowed inwind sectors centered at met.stationSpatial variability of surfacecharacteristicsYesNo – plume extend to infinityCausality effects considered?CALPUFFAERMODFeatureModel Applicability – Complex Terrain• EPA indicates AERMOD is suitable forcomplex terrain permitting applications• Main Issues with AERMOD– Use of a single meteorological field to characterizeflow for facility + all background sources– Use of surface characteristicsupwindofmeteorological station to characterizedownwindturbulence of all sources– Causality effects (plume go to infinity each hour)– Use of straight-line trajectoriesModel Applicability – Complex Terrain• EPA’s argument that AERMOD is OK incomplex flow regimes because only line ofsight impact matters is flawed for 2 majorreasons– NAAQS and PSD increments arecumulativestandards, not single facility standards.Interacting sources matter in assessingcompliance with the standards.– Non-peak concentrations are important inassessing significant contribution above/below theSILs.• Facility contribution abovethe SIL to a violation isconsidered a significant contribution370 375 380 385 390 395 400 405 410UTM East (km)4730473547404745475047554760

UTM North (km)42.8N42.9N112.5W112.4W112.3W112.2W112.1W-11003005007009001100130015001700190021002300250027002900310033003500370039004500Terrain (m)..UTM Zone: 12Datum: WGS-84Hemisphere: NSurface Meteorological Stations (used by Calmet)Upper air radiosonde station (used by Calme)Surface and Upper air Station (used by Aermod)10m Calmet wind field 6 Jan (23h00) - 7 Jan (05h00) 1993Wind Vectors (10m) – Complex Terrain with Channeled FlowCALPUFF – Cumulative Impacts370 375 380 385 390 395 400 405 410UTM East (km)4730473547404745475047554760

UTM No r th (km)42.8N42.9N112.5W112.4W112.3W112.2W112.1W-11003005007009001100130015001700190021002300250027002900310033003500370039004500TerrainElevation(m)..UTM Zone: 12Datum: WGS-84Hemisphere: NINKOMHOSPFMCCALPUFF shows channeling offlow. Background plumesinteract to produce cumulative impacts in valley.370 375 380 385 390 395 400 405 410UTM East (km)4730473547404745475047554760

UTM No r th (km)42.8N42.9N112.5W112.4W112.3W112.2W112.1W-11003005007009001100130015001700190021002300250027002900310033003500370039004500TerrainElevation(m)..UTM Zone: 12Datum: WGS-84Hemisphere: NAERMOD Impacts – INKOM SourceAERMOD produces straight-line impacts in terrainusing INKOM met. data. Note the lack of channelingof the flow into the NW-SE oriented valley.INKOMAERMOD – Cumulative Impacts370 375 380 385 390 395 400 405 410UTM East (km)4730473547404745475047554760

UTM No r th (km)42.8N42.9N112.5W112.4W112.3W112.2W112.1W-11003005007009001100130015001700190021002300250027002900310033003500370039004500TerrainElevation(m)..UTM Zone: 12Datum: WGS-84Hemisphere: NAERMOD produces incorrect cross-valley and downvalley impacts for HOSP and FMC sources. Note lackof plume interaction in AERMOD cumulative impacts.FMCHOSPINKOMModel Applicability• Coastal case– Sea breeze penetration over portion ofdomain– Relatively simple terrain– 3 sources– Most inland source considered as main“facility” source (met data based on it)• Demonstrates even in simple terrain,spatial variability can be importantSea Breeze Case – July 7, 1988 – 1:00pm LST260 280 300 320 340 360 380 400 420UTM East (km)4640466046804700472047404760

UTM North (km)12342.0N42.5N43.0N72.0W71.5W71.0W70.5W70.0WLandBreezeSeaBreeze260 280 300 320 340 360 380 400 420UTM East (km)4640466046804700472047404760

UTM North (km)12342.0N42.5N43.0N72.0W71.5W71.0W70.5W70.0WSea Breeze Case – July 7, 1988 – 1:00pm LST123Direction ofAERMOD PlumesComparison of AERMOD Plume Trajectories (Blue Arrows)with CALPUFF Trajectories (Filled Contours)CALPUFF Plumes - filled contoursModel Applicability• Random plume in AERMOD creates anupwind halo around every source thatresults in concentrations beingpredicted upwind• Can be problematic forcumulativeimpact assessmentsand assessingsignificant contributions to violations• Upwind concentrations can evenexceed downwind concentrations andSILs in AERMOD-100 -80 -60 -40 -20 0 20 40 60 80 100Distance (km)-100-80-60-40-20020406080100

Distance (km)0.00050.0010.00250.0050.010.020.040.080.160.320.641.22.4U(10m) = 4.5 m/sM-O L = 9000. mu* = 0.780 m/sw* = 0.0 m/sZi = 2449 mz0 = 1 mSourceWind DirectionAERMOD Predicted ConcentrationsSteady wind (4.5 m/s), Neutral stabilityAERMOD Mass Fraction Removed FromCoherent Plume to Random Plume0.00.10.20.30.40.50.60.70 10 20 30 40 50 60 70 80 90 100Distance (km)

Fraction RemovedLight Wind, ConvectiveSteady Wind, Neutral-40 -30 -20 -10 0 10 20 30 40 50Distance (km)2030405060708090100110

Distance (km)01234567891011121314151617181920212223242526AERMODStable Impingement TestsWD=340 degStack050100150200250300350400450500550600650700Terrain Elevation (m)-20 -10 0 10 20Distance (km)50607080

Distance (km)02468101214161820222426StackConc.(ug/m3)Wind Direction (340 deg.)Wide area of upwind conc. >>downwind concentrationsAERMOD – Problem: upwind concentrationslarger than downwind concentrationsSpatial Land Use VariabilityAERSURFACE Users Guide:• “Determining effective surfacecharacteristics for the purpose ofprocessing meteorological data for use with the AERMODmodel presents many challenges.”•“AERMOD is a steady-state plume model which assumesspatially uniform meteorological conditions across themodeling domain for each hour of meteorology, while landcover across the domain istypically very heterogeneous.”• “A sound understanding of the important physical processesrepresented in the AERMODmodel algorithms ... and thesensitivity of those algorithmsto surface characteristics isneeded in order to properly interpret the available data andmake an appropriate determination.”Data RepresentativenessAERMOD Implementation Guide (January 9, 2008)• “... data representativeness can be thought of interms of constructing realistic planetary boundarylayer (PBL) similarity profiles and adequatelycharacterizing the dispersive capacity of theatmosphere.”• “... the determination of representativeness of sitespecific data for AERMOD applications should alsoinclude an assessment of surface characteristics ofthe measurement and source locations and cannotbe based solely on proximity.”AERSURFACE Results (1km)AERSURFACE RoughnessLengths (m) for Juneby Wind Direction Sector.01.34.11.10Roughness lengths upwind ofmeasurement location characterizelocal boundary layer(Move location 1km East and smooth water disappears from characterization)AERMOD Dispersion• Surface Roughness for DispersionDownwind of Each Source• Averaged Surface RoughnessUpwind of Met. Measurements1 kmUp to 50kmMet LocationSource Location(s).01.01.34.11.10.11.10.34“Upwind” roughness at measurement locationdeterminesdownwinddispersion at sourcelocation in AERMODDownwind Roughness (m) forAERMOD Sources.34.11.01.10Source B.34.11.01.10Source ARoughness distribution near Source A isnot appropriate for modeling interactingSource B, nor is it appropriate for much ofthe 50km region around Source AAERMOD Sensitivity to SurfaceProperty Processing• Current Guidance: 1 km search radius for surfaceroughness, with upwind sectors determined by the user.Albedo and Bowen ratio determined for a 10km squarecentered at location.• Previous Guidance: 3 km search radius for surfaceroughness, albedo, and Bowen ratio with upwind sectorsdetermined by the user.• Significance of change characterized for actual permittingapplication– 4 stacks (2 at 231 m, 3 m and 27 m stack heights)– Nearly 3500 receptors– One full year of surface meteorological data (LouisvilleInternational Airport - SDF)AERMOD Sensitivity to SurfaceProperty Processing-3%-39%-43%-34%AERSURFACE 1-km Method(airport – onsite location)% Change in Peak Concentrations-0.3%103%123%89%AERSURFACE 1-km method– previous 3- km methodat Airport locationAnnual24-hr8-hr1-hrAveraging Time• Switch to AERSURACE with 1-km radius for z0 increased maximumshort term concentration predictions from AERMOD by more than afactor of 2• Using airport roughness instead of onsite roughness changesreduces AERMOD predicted short term concentrations by up to 43%AERMOD Sensitivity to AERMAPDATUM Error• EPA comment: Magnitude of changes in concentrationsdue to CALPUFF v5.8 were larger than expected• All models will be sensitive to changes in the inputparameters, including changes due to errors.• Example: coordinate transformation corrected inAERMAP• Significance of AERMAP changes characterized for anactual permitting application– 2 tall stacks (231 m stack height)– 2 short stacks (3 m and 27 m stack height)– Nearly 3500 receptorsAERMOD Sensitivity to AERMAPDATUM Error27 %-96 %-99 %-97 %-99 %Paired (correct location)% Change in Peak Concentrations[ (bad-corrected)/corrected ]30 %1784 %10246 %10980 %7307 %Paired (bad location)27 %43 %52 %7 %48 %Overall MaximumAnnual24-hr8-hr3-hr1-hrAveraging Time•Large differences frequentlyresult from code changes•Differences at specific locations(paired in space) can be especiallysensitiveModel Sensitivity• All dispersion models are sensitive tochanges in model inputs• Skill that an experienced, competentand objective modeler brings is ability tomake appropriate decisions on how amodel should be run• Regulatory guidance has a role inmodel applications, but cookbookformulas do not work well in manycasesCALPUFF Model Evaluation• Long-range transport– CAPTEXfield data for long-range transport distances– Inelfield data for intermediate transport distances– Wyomingdataset (long and short range – cumulative impacts)• Short-intermediate distances– Kincaid SF6: tracer releases from 187m stack in flat terrain– Lovett SO2: ambient monitoring on ridge near 145m stack inHudson river valley– PRIMEdatasets (building downwash)– Arkadelphia SF6: tracer releases from line source vents (potrooms)– Tennessee SO2: 2 years of monitoring of emissions from potroomsand stacks– Overwater and coastal datasets (5)• Ventura, Carpinteria, PismoBeach, Cameron (0.5 – 8 km)• Oresund (22 - 42 km)AERMOD Model Evaluation9 used in developing/tuning model algorithms7 used to develop/test PRIME downwash module common to ISC-PRIME,AERMOD, and CALPUFF(PRIME)(PRIME)(PRIME)(PRIME)(PRIME)(PRIME)(PRIME)(PRIME)WestvacoPrairie GrassTracyMillstoneMartin’s CreekLovettLee (wind tunnel)Kincaid SO2EOCRKincaid SF6Clifty CreekIndianapolisBaldwinDAECBowlineBowline (subset)AGAAlaskaIndependentDevelopmental17 AERMOD Evaluation DatasetsModel EvaluationAERMOD (non-PRIME) Developmental DatasetsYesYesYesYesYesOnsiteSigmaW0.89 (1hr)1.03 (3hr)1.01 (24hr)0.85 (annual)0.98 (3hr)0.94 (24hr)0.30 (annual)0.77 (1hr)1.11 (1hr)Modeled/ObservedRHC (EPA)0.46 mrelease145 m Stack187 m Stack187 m Stack84 m StackSourceType(s)OnsiteSigmaThetaMultipleSourceFacilitiesTerrainLandUseSiteYesNoneFlatRuralPrairie Grass(SO2)YesNoneComplexRuralLovett(SO2)YesNoneFlatRuralKincaid(SO2)YesNoneFlatRuralKincaid(SF6)YesNoneFlatUrbanIndianapolis(SF6)Model EvaluationAERMOD (non-PRIME) Independent Evaluation DatasetsYesYesNoNoNoOnsiteSigma-W1.06 (3hr)1.07 (24hr)1.59 (annual)1.04 (1hr)1.12 (3hr)1.78 (24hr)0.78 (annual)1.05 (3hr)0.67 (24hr)0.54 (annual)1.24 (3hr)0.97 (24hr)0.97 (annual)Modeled/ObservedRHC (EPA)183 m Stack91 m Stack122 m to 183m StacksThree 208 mStacksThree 184 mStacksSourceType(s)OnsiteSigma-ThetaMultipleSourceFacilitiesTerrainLandUseSiteYesNoneComplexRuralWestvaco(SO2)YesNoneComplexRuralTracy(SF6)YesNoneComplexRuralMartin’sCreek (SO2)NoNoneHalf ofStack Ht.RuralClifty Creek(SO2)NoNoneFlatRuralBaldwin(SO2)Model EvaluationAERMOD (PRIME) DatasetsNoNoNoNoYesNoOnsiteSigmaW0.51 (neutral)2.50 (stable)None64.8 mstackFlat“Rural”Lee (windtunnel)1.72 (1hr)YesNoneRooftop?FlatRuralEOCR(SF6)0.44 (46 m)1.32 (29 m)0.69 (46 m)0.25 (24 m)0.51 (1m)1.14 (1hr)1.43 (24hr)1.06(1hr)0.92 (1hr)Modeled/ObservedRHC (EPA)48m and29m stacks1 m,24m & 46mrooftopsTwo 87 mStacks39 m Stack10-25 mStackSourceType(s)OnsiteSigmaThetaMultipleSourceFacilitiesTerrainLandUseSiteNoNoneFlatCoastalMillstone(SF6)YesNoneFlatRuralDAEC(SF6)NoNoneFlatRuralBowline Point(SO2)YesNoneFlatRuralAlaska(SF6)NoNoneFlatRuralAGA(SF6)Model EvaluationNumber of building downwash studies with verylong buildings0Number in coastal locations, but not a fumigationscenario due to downwash(PRIME building downwash dataset)1Number in complex terrain involving multi-facilityimpacts0Number involving cumulative impact assessments017 AERMOD Evaluation Datasets•AERMOD has not been evaluated for use in assessing designconcentration limits arising from interacting facilities, especially those incomplex geographic areas•Evaluation datasets include evidence of underpredictionModel EvaluationAERMOD Results for Kincaid SF6 Tracer Dataset• Arc-maximum results (best if samplers capture maximum)• Kincaid SF6 distributed in Model Validation Kit (MVK) used in“Harmonisation of Atmospheric Dispersion Modelling for RegulatoryPurposes” workshops• MVK includes Quality Index (QI) values established for subset of the data– QI=0: disregard value– QI=1: most probably not the maximum value– QI=2: identified value may be near a local maximum– QI=3: identified value is a well-defined maximum0.64 (underprediction)MVK Subset for QI=30.68 (underprediction)MVK Subset for QI=2 or 30.77 (underprediction)EPA (all data?)Modeled/ Observed RHCKincaid SF6 DatasetModel EvaluationSO2Evaluation – Tennessee Smelter• SO2measured upwind and 300m downwind of facility• Primary sources: 4 potrooms (line sources), 4 banks of scrubberstacks (point sources)• Two years of data evaluated aspart of 1981 BLP evaluation whichresulted in BLP acceptance as aGuideline Model• Simulations with BLP, AERMOD and CALPUFF114.2116.2AERMOD19.617.1BLP18.515.8CALPUFF138Observed19771976Units: (μg/m3)Observed vs Predicted Q-Q Plots – 1977(1-hr Average SO2Concentrations)6070809095989999.899.999.9999.9991020304050607080901002003004005006007008009001000110012001300Cumulative Frequency (%) 

# Concentrations ( μ g/m 3 

# )ObservationsAERMODBLPCALPUFFOverwater Evaluation Datasets• OCD datasets (4 datasets)– Ventura, Carpinteria, Pismo Beach, Cameron– Test of overwater dispersionover 4-8 km range except forCarpinteria and Gaviota (<1km)– Both stable and unstable conditions• Oresund Experiment– Tracer experiments across 20 km-wide strait of Oresundbetween Denmark and Sweden– Tracer released at height of 95m or 115m– Transport distances to monitors: 22-44 kmCameron, Carpinteria, Pismo Beach, VenturaAll CALMET Configurations with CALPUFF Configuration ACALPUFF Configuration(Modeled Sigma-v >0.37 m/s)A -- Modeled Iy, CALPUFF Turbs, Draxler FyB -- Observed Iy, CALPUFF Turbs, Draxler FyE -- Modeled Iy, AERMOD Turbs, Draxler FyF -- Observed Iy, AERMOD Turbs, Draxler FyC -- Modeled Iy, CALPUFF Turbs, Variable TLyD -- Observed Iy, CALPUFF Turbs, Variable TLyG -- Modeled Iy, AERMOD Turbs, Variable TLyH -- Observed Iy, AERMOD Turbs, Variable TlyCALMET Configurationc0 – OCD overwater BL parameter modulec10d – COARE module (standard “deep water”)c10s – COARE module with shallow water adj.c11 – COARE module with wave option 1c12 – COARE module with wave option 2OCD5 with Modeled Iy (Sigma-v >0.37 m/s)OCDCALPUFF0.660.54OCD50.840.62CALPUFF(AERMOD Turbulence Profile)0.830.60CALPUFF(CALPUFF Turbulence Profile)CorrelationFraction withinfactor of 2Observed Iy0.710.54OCD50.850.67CALPUFF(AERMOD Turbulence Profile)0.840.66CALPUFF(CALPUFF Turbulence Profile)CorrelationFraction withinfactor of 2Modeled IyFactor of 2 and Correlation statistics310 320 330 340 350 360 370 380 390UTM East (km) Zone33N, Datum: EUR-M614061506160617061806190620062106220

UTM North (km) Zone 33N, Datum: EUR-MGladsaxeBarsebackSnow/IceTundraBarrenWetlandWaterForestRangeAgricultureUrban/Built-UpLand Use101520253035404550556065707580859095100....Strait of OresundDenmarkSwedenSampler LocationsTracer ReleasesTerrain Contour 25mOresundCALMET - CALPUFF Configuration-Zi1 – No Turb Advection, Maul-CarsonMixing Ht-Zi1OW – No Turb Advection, Maul-CarsonMixing Ht , Obs Overwater-Zi2 – No Turb Advection, BatchvarovaGryning Mixing Ht-Zi1OW – No Turb Advection,Batchvarova-Gryning Mixing Ht ,Obs Overwater-800Zi1 –Turb Advection (800s),Maul-Carson Mixing Ht-800Zi1OW –Turb Advection (800s),Maul-Carson Mixing Ht ,Obs Overwater-800Zi2 –Turb Advection (800s),Batchvarova-Gryning Mixing Ht-800Zi1OW –Turb Advection (800s),Batchvarova-Gryning Mixing Ht ,Obs OverwaterNo turbulenceadvectionWith turbulenceadvection00.20.40.60.811.21.41.61.820 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2Bridger IMPROVE [SO4]. Units: ug/m **3 of SO4

CALPUFF Predicted [SO4]. Units: ug/m**3 of SO4CALPUFF PERFORMANCE PREDICTING SO4W/ BCs and ALM (BRIDGER IMPROVE SITE)2 x overprediction2 x underpredictionprediction =observations00.10.20.30.40.50.60 0.1 0.2 0.3 0.4 0.5 0.6Bridger IMPROVE [NO3]. Units: ug/m**3 of NO3

CALPUFF Predicted [NO3]. Units: ug/m**3 of NO 3CALPUFF PERFORMANCE PREDICTING NO3W/ BCs and ALM (BRIDGER IMPROVE SITE)2 x overprediction2x underpredictionprediction =observationOBSERVED AND PREDICTED SO4,NO3and SO2(ug/m3)90%.207.172.585.366SO278%.081.082.0922.0978NO394%.248.286.492.453SO4Within2xPredSDObsSDPredMeanObsMeanSpeciesOBSERVED AND PREDICTED Bext(Mm-1)BRIDGER TRANSMISSOMETER SITE--7.25.54.6StandardDeviation-0.030-0.01724.722.523.2MeanFractionalBiasMethod 6FractionalBiasMethod 2ObsCALPUFFMethod 6CALPUFFMethod 2VariableOBSERVED and PREDICTED ANNUAL WET Sand N DEPOSITION (kg/ha/yr) AT NADP SITES0.720.73GypsumS1.241.18GypsumN0.790.97South PassS1.281.43South PassN0.831.11Sinks CanyonS1.361.34Sinks CanyonN0.690.75PinedaleS1.170.99PinedaleNPredictedWet FluxObservedWet FluxSiteSpeciesModel Evaluation Summary• AERMOD has been shown to perform well in certaincircumstances but has shown underprediction inseveral of the EPA datasets.• No evaluation data presented by EPA for cumulativeimpacts assessments or for upwind impacts predictedby random plume, or multi-source impacts• Most evaluations method different from typicalpermitting study (i.e., observed turbulence rather thanpredicted turbulence)• AERMOD model formulation makes it unsuitable formany non-steady-state situationsConsistency vs. AccuracyParagraph 1(d) of theGuideline:“The model that most accurately estimatesconcentrations in the area of interestis always sought. However, it is clear from the needs expressed by the States andEPA Regional Offices, by many industriesand trade associations, and also by thedeliberations of Congress, thatconsistency in the selection and application ofmodels and data based should be sought, even in case-by-case analyses.Consistency ensures that air quality control agencies and the general public have acommon basis for estimating pollutant concentrations, assessing control strategiesand specifying emission limits.Such consistency is not, however, promoted at theexpense of model and data base accuracy. TheGuidelineprovides a consistent basisfor selection of the model accurate models and data basesfor use in air quality assessments.”Summary• AERMOD should not automatically be preferred overCALPUFF in applications involving non-steady-stateapplication• AERMOD has significant issues with cumulativeimpacts• AERMOD sensitive to specification of land use andsurface properties may involve substantial errorassociated with its inability to vary surface propertiesappropriately for the facility source and especiallybackground sources.• The intent of the GAQM should be followed to allowCALPUFF use wherever complex flow or non-steadystate conditions are important