Model Evaluation and Assessment ALBERT EINSTEINALBERT EINSTEIN: Things should be made as simple as...
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Transcript of Model Evaluation and Assessment ALBERT EINSTEINALBERT EINSTEIN: Things should be made as simple as...
Model Evaluation and Assessment
ALBERT EINSTEIN: Things should be made as simple as possible, but not any simpler.
Theodore A. HaighConfederated Tribes of the Umatilla Indian
ReservationEnvironmental Science & Technology Program
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Objectives Types of models
What choices do you have? Model input data
What needs to go into your chosen model? Model output data
What comes out of your chosen model?
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What data?
Meteorological Demographic
Lifestyles Accurate
for local population
All factors accounted for
Topographic Local Regional
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Models & Testing
Theory Limitations of
the model Constraints
Reality You don’t
know unless you test
Agreement?
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Common Sense Does it make sense?
Do predicted quantities have believable values?
Predictions How long will the
contamination persist? How far will it spread? How much is present?
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Agreement Can this model
be verified? In-house check Check with
another group You run model
with similar data Get similar
results? Errors can be
identified and remedied
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What’s IN/NOT IN the Model Weather data
Wind Direction and
speed Historical record
long enough Rain Snow Humidity Temperature
Terrain data Health effects Sources Urban effects Chemistry
Kinetics Photochemistry Additional
sources
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Predicting Measurements agree
with model? Values from the
model seem okay? Level of uncertainty
with predictions Estimates of
dispersion Conservative Liberal
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Alternative Methods
Always more than one way to do Anything
Types of models Physical Numerical Empirical Dispersion
Gaussian Eulerian Lagrangian
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Model Limitations
Physical Stability difficult to
simulate Scale effects not well
known Vertical & horizontal
turbulence damped by walls
Measurement is tricky
Numerical Assume theory is
well defined Require significant
CPU resources and time
Little validation data available
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Model Limitations (cont.) Empirical models
Based upon analysis of source, meteorological, and air quality data
Gaussian dispersion model Mathematical
expression using Gaussian distributions to relate emissions of pollutants to ambient concentrations