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

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

The Sun’s impact on Earth’s surface

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 ModelDomain ScaleResolution Microscale200m x 200mx 100 m5 m Mesoscale (urban)100Km x 100Km x 5Km2 Km Regional1000Km x 1000Km x 10Km20 Km Synoptic (continental)3000Km x 3000Km x 20Km80 Km Global65000Km x65000Km x20Km

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

Large Scale Advection: Movement with bulk flow (wind)

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

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

Surface conditions TerrainTopography Planetary boundary layer and surface roughness

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

Turbulence & eddies Moving objects move air molecules - cause currents

Physics & chemistry meet Reflection, absorption and deposition

Which Chemicals? Source type Chemical Reactions CH4 + OH ---> CH3 + H2O CH3 + O2 ---> CH3OO CH3OO + NO ---> CH3O + NO2 CH3O + O2 ---> HCHO + HO2 h ( HCO + H HCO + O2 ---> CO + HOO H + O2 ---> HOO Mechanisms: Oxidation and reduction, thermal, photochemical, hydrolysis

Understand model limits & assumptions

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

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

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

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

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