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 Suns impact on Earths 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 Models 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
