1. Introduction to Modeling – Part I Sarah Kelly ITEP Sarah Kelly ITEP

2. 2 Why Model?  To answer questions  source emitting 250 tons/year of PM 2.5 5 miles west of reservation: effect on air we breathe?  What if same source built on my reservation?  Or 10 miles north?  What if it emits 500 tons/year of PM 2.5 ?  To answer questions  source emitting 250 tons/year of PM 2.5 5 miles west of reservation: effect on air we breathe?  What if same source built on my reservation?  Or 10 miles north?  What if it emits 500 tons/year of PM 2.5 ?

3. 3 Why Model? (cont.)  To answer questions (cont.)  Where does pollution come from?  About pollution emitted by facility on or near my reservation  What kind and how much?  Once emitted, where does it go?  Where should I locate monitors?  Where is regional haze on my reservation coming from?  To answer questions (cont.)  Where does pollution come from?  About pollution emitted by facility on or near my reservation  What kind and how much?  Once emitted, where does it go?  Where should I locate monitors?  Where is regional haze on my reservation coming from?

4. 4 Why Model? (cont.)  To Predict Future  Need to “calibrate” with reality  Check against data collected in field  To Interpret  Study system and/or organize field data  Does not require calibration, but “reality checks” always useful  To Predict Future  Need to “calibrate” with reality  Check against data collected in field  To Interpret  Study system and/or organize field data  Does not require calibration, but “reality checks” always useful

5. 5 Why Model? (cont.)  Because EPA recommends it  New Source Review (NSR) Permits  PSD - estimate effects on increments  Non-attainment - Choose strategies to reduce pollution to attain NAAQS  Minor Sources  TIP Development  To understand a complex system  Weather  Air pollution  Because EPA recommends it  New Source Review (NSR) Permits  PSD - estimate effects on increments  Non-attainment - Choose strategies to reduce pollution to attain NAAQS  Minor Sources  TIP Development  To understand a complex system  Weather  Air pollution

6. 6 What is a Model?  Any approximation of a field situation  Empirical model  Derived from information gained from observations or experiments  Mathematical model  Simulates field situation indirectly using equations  Workshop focuses on mathematical and empirical models  Any approximation of a field situation  Empirical model  Derived from information gained from observations or experiments  Mathematical model  Simulates field situation indirectly using equations  Workshop focuses on mathematical and empirical models

7. 7 What is a Model? (cont.)  Mathematical models have  Governing equation – represents physical processes occurring in system  Boundary equations (conditions)  Initial conditions (for time- dependent problems)  Mathematical models have  Governing equation – represents physical processes occurring in system  Boundary equations (conditions)  Initial conditions (for time- dependent problems) X = Q * K * V * D * exp[-0.5 * (y/  y)2 ] / (2 * Β  * u s *  y *  z)

8. 8 What is a Computer Model?  Set of commands used to solve mathematical or empirical model on computer  Computer programs are generic – written once  Model is designed each time you enter a set of boundary and initial conditions, and site- specific values, into computer program  Set of commands used to solve mathematical or empirical model on computer  Computer programs are generic – written once  Model is designed each time you enter a set of boundary and initial conditions, and site- specific values, into computer program

9. 9 Computer Models  Commercial modeling programs  Make it easier for users to communicate with computer code and enter data  Often have graphical interfaces  Ease data entry  Eases visualization of modeling results  Commercial modeling programs  Make it easier for users to communicate with computer code and enter data  Often have graphical interfaces  Ease data entry  Eases visualization of modeling results

10. 10 Computer Models (cont.)  Graphics packages – Picture instead of number grid PM 10 Concentrations

11. 11 Computer Model – Dangers  Modern modeling programs and graphics packages easy to use, produce impressive pictures and graphs  Model only as good as site- specific data, initial and boundary conditions you enter  Garbage IN = Garbage OUT  Modern modeling programs and graphics packages easy to use, produce impressive pictures and graphs  Model only as good as site- specific data, initial and boundary conditions you enter  Garbage IN = Garbage OUT

12. 12 What type of model should you use?  Step One: Establish your purpose!  Make predictions? Interpret and better understand what’s going on?  What do you want to learn? What questions do you want to answer?  Is modeling the best way to answer your questions?  Step Two: What type of model should you use?  Step One: Establish your purpose!  Make predictions? Interpret and better understand what’s going on?  What do you want to learn? What questions do you want to answer?  Is modeling the best way to answer your questions?  Step Two: What type of model should you use?

13. 13 Models – Two Opinions  Models are worthless  Too expensive to run, require too much data  Real world too complex  Can never be proven “correct”  Models are essential for complex analyses  Combines human judgment with computer power  Provide framework for analyzing large data sets  Good way to make informed analysis or prediction  Models are worthless  Too expensive to run, require too much data  Real world too complex  Can never be proven “correct”  Models are essential for complex analyses  Combines human judgment with computer power  Provide framework for analyzing large data sets  Good way to make informed analysis or prediction

14. 14 EPA’s Preferred Models  40 CFR Part 51 – Guideline on Air Quality Models, Appendix W  http://www.epa.gov/scram001/g uidance_permit.htm http://www.epa.gov/scram001/g uidance_permit.htm  If using preferred models, don’t need to demonstrate applicability  40 CFR Part 51 – Guideline on Air Quality Models, Appendix W  http://www.epa.gov/scram001/g uidance_permit.htm http://www.epa.gov/scram001/g uidance_permit.htm  If using preferred models, don’t need to demonstrate applicability

15. 15 EPA’s Preferred Models  AERMOD – recommended for regulatory use for  Point, volume or area sources  Rural or urban areas  Simple or complex terrain  Transport distance up to 50 km (31 miles)  For distances over 50 km – CALPUFF (not covered here)  AERMOD – recommended for regulatory use for  Point, volume or area sources  Rural or urban areas  Simple or complex terrain  Transport distance up to 50 km (31 miles)  For distances over 50 km – CALPUFF (not covered here)

16. 16 Summary  Know why you want to use a model  Research: What kind of model will answer the questions you have?  Gather good information to use in your model  Use EPA preferred models if necessary  Know why you want to use a model  Research: What kind of model will answer the questions you have?  Gather good information to use in your model  Use EPA preferred models if necessary