Introduction to Modeling – Part II Rodney S. Skeen, Ph.D., P.E. Confederated Tribes, Umatilla...

Introduction to Modeling –

Part II

Rodney S. Skeen, Ph.D., P.E.Confederated Tribes, Umatilla

Rodney S. Skeen, Ph.D., P.E.Confederated Tribes, Umatilla

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ObjectiveObjective Provide a general understanding of

regulatory air dispersion modeling tools

Provide a general understanding of regulatory air dispersion modeling tools

Where will it go and should I care?

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Uses for Air ModelsUses for Air Models

Facility permitting EXAMPLE: Site a new source, regulatory

requirements and thresholds Regulatory and policy assessments

EXAMPLE: Decide between options for national auto emissions

Identify potential sources for a daily air quality exceedance

Forecasts pollutant concentrations EXAMPLE: Air quality index forecasting

Facility permitting EXAMPLE: Site a new source, regulatory

requirements and thresholds Regulatory and policy assessments

EXAMPLE: Decide between options for national auto emissions

Identify potential sources for a daily air quality exceedance

Forecasts pollutant concentrations EXAMPLE: Air quality index forecasting

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Air Pollution ModelsAir Pollution Models

Mathematically simulate physical and chemical processes to predict pollution movement

Modeling approach varies to fit requirements Computational speed Size of model region Spatial and temporal resolution Time period of concern Controlling processes

POINT: One size DOES NOT fit all

Mathematically simulate physical and chemical processes to predict pollution movement

Modeling approach varies to fit requirements Computational speed Size of model region Spatial and temporal resolution Time period of concern Controlling processes

POINT: One size DOES NOT fit all

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Model’s View of WorldModel’s View of World

COPC Particles

Meteorology

Topography and Geography

COPC VaporsCOPC Vapors

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Model’s View of World (cont…)Model’s View of World (cont…)

COPC phases Vapor Particle Particle-bound

Deposition mechanisms Wet Dry

COPC phases Vapor Particle Particle-bound

Deposition mechanisms Wet Dry

Meteorology Wind Speed, Direction Temperature profile Solar energy Precipitation

Topography/Geography

Meteorology Wind Speed, Direction Temperature profile Solar energy Precipitation

Topography/Geography

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Model’s View of World (cont…)Model’s View of World (cont…)

Calculate concentration map Calculate concentration map

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Controlling Processes (1)Controlling Processes (1)

Advection: Movement with bulk flow (wind)

Advection: Movement with bulk flow (wind)

Diffusion: Molecular mixing because of concentration differences

Diffusion: Molecular mixing because of concentration differences

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Plume rise Plume rise Turbulence Turbulence

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Dispersion: Total plume spread caused by three dimensional advection (turbulence) and diffusion

Dispersion: Total plume spread caused by three dimensional advection (turbulence) and diffusion

This…

…or That

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Controlling Processes (4)Controlling Processes (4) Chemical Reaction Chemical Reaction Flow restrictions Flow restrictions

CH4 + OH ---> CH3 + H2O CH3 + O2 ---> CH3OO

CH3OO + NO ---> CH3O + NO2 CH3O + O2 ---> HCHO + HO2

h ( <330 nm) HCHO ---> HCO + H

HCO + O2 ---> CO + HOO H + O2 ---> HOO

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Controlling Process (5)Controlling Process (5)

Deposition Deposition

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Many Models AvailableMany Models Available

Dispersion Models: HYSPLIT, AERMOD, ISCST3, CALPUF

Photochemical Models: CMAQ, CAMx, REMSAD, UAM-V®

Receptor Models: CMB, UNMIX, PMF

Many, many others

Dispersion Models: HYSPLIT, AERMOD, ISCST3, CALPUF

Photochemical Models: CMAQ, CAMx, REMSAD, UAM-V®

Receptor Models: CMB, UNMIX, PMF

Many, many others

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Model TypesModel Types

Dispersion Models: Estimate pollutants at ground level receptors

Photochemical Models: Estimate regional air quality, predicts chemical reactions

Receptor Models: Estimate contribution of multiple sources to receptor location based on multiple measurements at receptor

Dispersion Models: Estimate pollutants at ground level receptors

Photochemical Models: Estimate regional air quality, predicts chemical reactions

Receptor Models: Estimate contribution of multiple sources to receptor location based on multiple measurements at receptor

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Dispersion Models - AERMOD

Dispersion Models - AERMOD

Steady-state (Gaussian) plume model Planetary boundary layer turbulence

structure and scaling Multiple sources, source types Building downwash Limited to 50 km radius Replaced ISCST3 as preferential

dispersion model

Steady-state (Gaussian) plume model Planetary boundary layer turbulence

structure and scaling Multiple sources, source types Building downwash Limited to 50 km radius Replaced ISCST3 as preferential

dispersion model

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Planetary Boundary LayerPlanetary Boundary Layer

ConvectiveBoundary

Layer

StableBoundary

Layer

PlanetaryBoundary

Layer

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Gaussian Plume ModelGaussian Plume Model Plume assumed to spread in a

Gaussian manner in both horizontal and vertical dimension

Plume moves in single direction

Plume assumed to spread in a Gaussian manner in both horizontal and vertical dimension

Plume moves in single direction

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21( )

2

y

f y eσ

σ π

⎛ ⎞⎛ ⎞⎜ ⎟− ⋅⎜ ⎟⎜ ⎟⎝ ⎠⎝ ⎠=

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Gaussian Plume ModelGaussian Plume Model Meteorological conditions sets

dispersion in y- and z-dimensions Expressed in standard deviation (σ)

Meteorological conditions sets dispersion in y- and z-dimensions

Expressed in standard deviation (σ)

Gaussian Distribution

-10

0

10

20

30

40

50

60

70

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2

0.1

0.25

1

1.25

Standard Deviation

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AERMOD ApplicationsAERMOD Applications

Predicting near source impacts of a contaminant plume (< 50 km).

EXAMPLE: Permitting a new source

Predicting near source impacts of a contaminant plume (< 50 km).

EXAMPLE: Permitting a new source

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Dispersion Model - CALPUFDispersion Model - CALPUF

Non-steady state model Time/space varying meteorological

conditions Gaussian “puff” approach to dispersion

Applicable to hundreds of meters EPA preferred model for simulating long-

range transport of pollutants

Primary and secondary pollutants Many features similar to AERMOD

Non-steady state model Time/space varying meteorological

conditions Gaussian “puff” approach to dispersion

Applicable to hundreds of meters EPA preferred model for simulating long-

range transport of pollutants

Primary and secondary pollutants Many features similar to AERMOD

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Gaussian Puff ModelGaussian Puff Model

“Puffs” of pollutants are acted upon by hourly meteorological data

“Puffs” of pollutants are acted upon by hourly meteorological data

W1

W2

S.S. Plume

Puff

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Many features similar to AERMOD Multiple sources and source types Building downwash Plume rise Complex terrain

Many features similar to AERMOD Multiple sources and source types Building downwash Plume rise Complex terrain

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Unique Applications Class I impact studies Evaluate impacts of forest fire Reservation wide impact study

(multiple sources) Overwater transport and coastal

situations

Unique Applications Class I impact studies Evaluate impacts of forest fire Reservation wide impact study

(multiple sources) Overwater transport and coastal

situations

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Dispersion Model - HYSPLIT


HYSPLIT a modeling tool used for computing both Wind trajectories in three dimensions Complex pollutant dispersion, deposition

patterns Provides short-term forecasts using

National Weather Service data

HYSPLIT a modeling tool used for computing both Wind trajectories in three dimensions Complex pollutant dispersion, deposition

patterns Provides short-term forecasts using

National Weather Service data

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Forward predication (dispersion) in short-term

Forward predication (dispersion) in short-term

Do I allow a proscribed burn?

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Where did it come from? Where did it come from?

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SummarySummary Models convert numerical representation of

system to concentration map Scale of problem Controlling processes Available data

Many specialty models are available for specific applications – know your need AERMOD: Long-term, within 50 km CALPUF: Long-term, >50 km, more complex weather HYSPLIT: Short-term impacts

Models convert numerical representation of system to concentration map Scale of problem Controlling processes Available data

Many specialty models are available for specific applications – know your need AERMOD: Long-term, within 50 km CALPUF: Long-term, >50 km, more complex weather HYSPLIT: Short-term impacts

Introduction to Modeling – Part II Rodney S. Skeen, Ph.D., P.E. Confederated Tribes, Umatilla...

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