intro to modeling – terms & concepts
DESCRIPTION
Intro to Modeling – Terms & concepts. Marti Blad, Ph.D., P.E. ITEP 5.29.13. AP models vary in complexity. Mathematically simulate environmental processes to predict pollution movement and concentrations More than one way to describe w #’s Physical, Chemical and Biological World - PowerPoint PPT PresentationTRANSCRIPT
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Intro to Modeling – Terms & concepts
Marti Blad, Ph.D., P.E.ITEP 5.29.13
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AP models vary in complexity
• Mathematically simulate environmental processes to predict pollution movement and concentrations– More than one way to describe w #’s
• Physical, Chemical and Biological World• Solar radiation is energy or process driver
– The Sun
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The Sun’s impact on Earth’s surface
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AP Physical Scale• Determine Limitations & Assumptions
– Scale = size of area modeled– Resolution = level of detail– Other Physical processes; meteorology, source types– Topography; urban vs rural, water bodies, mountains– Detail for Inputs and outputs of model
Model Domain Scale ResolutionMicroscale 200m x 200mx 100 m 5 m
Mesoscale (urban) 100Km x 100Km x 5Km 2 Km
Regional 1000Km x 1000Km x 10Km 20 Km
Synoptic (continental) 3000Km x 3000Km x 20Km 80 Km
Global 65000Km x65000Km x20Km
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AP Model Time periods• Long term or short term temporal period• Affects resolution (spatial detail)
– Data input and data output– Minutes vs hours vs days
• Physical processes match time scales– Atmospheric temperature profiles
• Chemical reactions affected by solar intensity– Changes every second!
• Emission source rates continuous or changing– Equilibrium or steady state
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Large Scale
• Advection: Movement with bulk flow (wind)
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Small Scale
• Diffusion: Molecular mixing because of concentration differences.
• High concentration moves to lower concentration
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Where large and small meet
• Dispersion: Total plume spread caused by three dimensional advection (turbulence) and diffusion
This…
…or That
Dispersion affected by stack height, building locations, and topography
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Surface conditions
TerrainTopography
Planetary boundary layer and surface roughness
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Convection• Plume rise = buoyancy
Ambient vs exit temperature affect air movement
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Turbulence & eddies
Moving objects move air molecules - cause currents
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Physics & chemistry meet
• Reflection, absorption and deposition
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Which Chemicals?• Source type• Chemical Reactions
CH4 + OH ---> CH3 + H2O CH3 + O2 ---> CH3OO
CH3OO + NO ---> CH3O + NO2 CH3O + O2 ---> HCHO + HO2
hn (l <330 nm) HCHO ---> HCO + H
HCO + O2 ---> CO + HOO H + O2 ---> HOO
Mechanisms: Oxidation and reduction, thermal, photochemical, hydrolysis
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Understand model limits & assumptions
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Many Models Available
• 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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Terms & Concept review
• Advection• Diffusion• Domain (area vs computer)• Conservative• Reactive• Kinetic• Discrete (vs continuous)• Receptor
• Albedo• Anthropogenic• Deposition
– Wet vs Dry
• Lumped parameters• Algorithm• Laminar• Photochemical
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What is purpose in modeling?
Physical, Chemical, and Biological processes can be modeled
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Model’s View of World• Chemical Processes• Reactive or conservative• Chemical of Concern• Biological impact• Mathematical Processes
– Eulerian, Lagrangian, – Gaussian– Time scale
• Physical Processes• Meteorology
– Wind Speed, Direction– Solar energy = reactions– Precipitation
• Topography/Geography• Deposition mechanisms• Source Type
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Summary• Models convert numerical representation of system to
concentration map or picture– Scale of problem; time and space– Controlling processes; meteorology, topography, and source– Available data; quality and quantity