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Intro to Modeling – Terms & concepts

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

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Intro to Modeling – Terms & concepts

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  1. Intro to Modeling – Terms & concepts Marti Blad, Ph.D., P.E. ITEP 5.29.13

  2. 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

  3. The Sun’s impact on Earth’s surface

  4. 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

  5. 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

  6. Large Scale • Advection: Movement with bulk flow (wind)

  7. Small Scale • Diffusion: Molecular mixing because of concentration differences. • High concentration moves to lower concentration

  8. 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

  9. Surface conditions Topography Terrain Planetary boundary layer and surface roughness

  10. Convection • Plume rise = buoyancy Ambient vs exit temperature affect air movement

  11. Turbulence & eddies Moving objects move air molecules - cause currents

  12. Physics & chemistry meet • Reflection, absorption and deposition

  13. 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: Oxidationand reduction, thermal, photochemical, hydrolysis

  14. Understand model limits & assumptions

  15. Many Models Available • Dispersion Models: HYSPLIT, AERMOD, ISCST3, CALPUF • Photochemical Models: CMAQ, CAMx, REMSAD, UAM-V® • Receptor Models: CMB, UNMIX, PMF • Many, many others

  16. Terms & Concept review Albedo Anthropogenic Deposition Wet vs Dry Lumped parameters Algorithm Laminar Photochemical • Advection • Diffusion • Domain (area vs computer) • Conservative • Reactive • Kinetic • Discrete (vs continuous) • Receptor

  17. What is purpose in modeling? Physical, Chemical, and Biological processes can be modeled

  18. 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

  19. 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

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