UNCLASSIFIED Assimilating Concentration Data into Dispersion Models with a Genetic Algorithm Sue...
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UNCLASSIFIED
Assimilating Concentration Data into Dispersion Models
with a Genetic AlgorithmSue Ellen HauptKerrie J. Long
Anke Beyer-LoutGeorge S. Young
7th Conference on Artificial Intelligence Applications to Environmental Science Phoenix, AZ - January 12, 2009
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Assimilation to Refine Hazard Areas
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Assimilation Theory
Dynamical Prediction System:
Assimilation Process:
Objectives:1. Determine realization characteristics2. Assimilate data into forecast
Can separate into wind and concentration equations
t
x
Mx η
( )Gt
0 fx
Mx η x ,x
( , , )o fvG C C
t
o f
v v
vM (v)v η v , v
( ) ( , , )o fC
CC G C C
t
o f
C CM v η v , v
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GA-Var Assimilation Procedure
Concentration Assimilation
1. Use “guessed” wind and source data to predict concentration.
2. Compute difference (innovation) between concentration prediction and observation.
3. Use GA-Var to update wind and source variables.
Repeat until converged
dynamically assimilate one time before going on to next time
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Meandering Plume
We wish to assimilate a puff in a meandering wind field to reconstruct time dependent wind by assimilating
observations of dispersed contaminant concentrations
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Problem Set-Up
Experimental Design
• Identical Twin • Sinusoidally varying wind
field• Puff dispersion• Source characteristics
are known• Seek to compute wind
direction given concentration observations
Techniques
1.Genetic Algorithm Variational (GA-Var)• Field based• Eulerian
2.Feature Extraction with Nudging (FEWN)• Entity Based• Lagrangian
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Comparison
Exact Solution
FEWN
GA-Var
Anke Beyer-Lout
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Comparison
Wind Direction Puff Centroid
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Sensitivity to Resolution
FEWN GA-Var
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Meandering Puff Conclusions
• Both Entity and Field approaches are useful for assimilating wind from concentration observations
• GA is useful for minimizing difficult cost function• GA can be used within the variational
formalism:
GA-Var
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The Shallow Water Assimilation: TusseyPuff
2-D shallow water model
Gaussian Puff model
Wind field
Concentration field
TusseyPuff
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Identical Twin Experiment
• Random observation stations
• Add noise (5%)
• Fit Gaussian distribution to observed concentrations
• Observations: wind, puff location, amplitude and
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GA-Var Results
13
Me
an
Ab
solu
te E
rror
Sigma LocationSource Strength
Time (s) Time (s) Time (s)M
agn
itu
de
of
Lo
cati
on
Err
or
[m]
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GA-Var in TusseyPuff Conclusions
• GA-Var can recovered time dependent puff parameters:
X-locationY-location Sigmasource strength
• Assimilate concentration observations by using wind field observations despite one-way coupling
14
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Conclusions
GA-Var is a useful technique for assimilating concentration data into0 a time-varying wind field
Process involves:
1. Determine the realization characteristics2. Assimilate the data into that current prediction
Can recover wind information given concentration observations
Produces better concentration predictions Could have broader applicability
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Questions?