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Forecasting Ozone in Treasure Valley using CART
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Forecasting Ozone in Treasure Valley using CART
Idaho DEQJune 3, 2011
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Ozone in Treasure Valley
Ozone in Treasure Valley
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2001
2002
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Year
Ozo
ne
Co
nce
ntr
atio
n
(pp
b)
8hr max
4th Highest
3year Ave 4thHighest
Standard
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Treasure Valley Ozone Monthly Statistics2001-2008
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MAY JUN JUL AUG SEP
Month
Ozo
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(pp
b)
Month Average
Ave Month Max
Month Max
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Forecasting for AQI and CRB
• Daily AQI forecast for public• Daily AQI forecast for residential burning bans (AQI<60
outdoor, AQI <74 all burns)• Forecast for Crop Residual Burning • Regional offices utilize AIRPACT, WRF data, apply various
methods for the forecasting • Need more reliable, easy to use tools
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CART Model
• Classification And Regression Tree (CART) is a statistical procedure designed to classify data into dissimilar groups.
• CART helps to develop a decision tree to predict pollutant concentrations based predictor variables that are well correlated with pollutant concentrations.
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Forecasting Methods
Methods Development Effort Operational Effort Accuracy
Persistency Low Low Low
Climatology Low-Moderate Low Low
Criteria Low-Moderate Low Low-Moderate
CART Moderate Low Moderate-high
Regression Moderate Moderate Moderate-high
Neural Networks Moderate-high Moderate Moderate-high
3-D Air Quality
Models
Very High Moderate-high Moderate-high
Phenomenological
/Intuition
High Moderate High
From Guidelines for Developing an Air Quality (Ozone and PM2.5) Forecasting Program. EPA-456/R-03-002 June 20036
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Data
• Eight year ozone data (2001-2008)• Eight year meteorological data including
surface data and upper air data: temperature, wind, humidity, pressure, etc.
• WRF forecasting data
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Correlation TablePositive correlation
No correlation
Negative correlation
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G=Green 0-59ppbY=Yellow 60-75 ppbO=Orange 76-95ppbR=Red 96-115ppbP-Purple 116-374ppb
CART tree for Treasure Valley Ozone Forecasting (1)Observation Data: Year 2001-2008, May-Aug
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G=Green 0-59ppbY=Yellow 60-75 ppbO=Orange 76-95ppbR=Red 96-115ppbP-Purple 116-374ppb
CART tree for Treasure Valley Ozone Forecasting (2)Observation Data: Year 2001-2008, May-Aug
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Performance EvaluationTS Performance
Total days 79
Observed Green Days 59
Observed Yellow Days 20
forecasted Green 52
Forecasted G for G 48
Forecasted Yellow 21
Forecasted Y for G 4
Forecasted G for Y 4
Forecasted Y for Y 17
Accuracy of Green 81%
Accuracy for Yellow 85%
Over forecasting 7%
Under forecasting 20%11
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Performance
Ozone Forecast for Treasure ValleyOzone season 2010
0.0300.0350.0400.0450.0500.0550.0600.0650.0700.0750.080
6/6/
2010
6/8/
2010
6/10
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6/12
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6/14
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6/16
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6/18
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6/20
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6/22
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6/24
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6/26
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6/28
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7/2/
2010
7/4/
2010
7/6/
2010
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7/10
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7/12
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7/14
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7/16
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7/18
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8/25
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9/2/
2010
Date
Ozo
ne
(p
pm
)
Obs Max 8hr Max TS Forecast
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Source of Errors
• Small changes near the split point may end larger errors.
• Bias in the meteorological forecast.• Emission changes. e.g. Holidays, economy driven
sources.• Boundary conditions. e.g. Stratosphere intrusion (ST)
due to stratosphere-troposphere exchange (STE); long range transport.
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An unusual Ozone Episode in May 2011Graphs From AIRPACT
Conditions on May 15, 2011 in Treasure Valley:A cold front was reaching the areaMax temperature ~ 53°F, breezy, rainMax 8hour average O3 reached 63ppb in early afternoon, the highest in the month.
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Monthly average relative humidity was 26.7%Average 6 year Relative humidity in May is 38.4%. (average from 10:00am-6:00pm)
Warm (~80’s °F) and Dry
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Weekend Effect
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CART- Limitations
• Requires large set of data, a modest amount of expertise and effort to develop.
• Small changes in predictor variables may produce large changes in the predictions.
• Does not predict unusual events.• Requires periodic updates due to emission
and land use changes.
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Future Work
• Improve the model for Boise • Experiment for Coeur d’Alene• Explore more parameters• Study for unusual events.
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