Geographic Scale -The explicit physical scale of an air quality model affects more abstract levels of scale of data inputs Atmospheric Chemistry -The dynamic interaction of chemicals and meteorology Modeling Visibility in the National Parks -Modeling at the regional scale – Long range transport in addition to chemistry Using the Results, Dealing With Uncertainty -Modeling complex systems rarely yields definitive results Tyler Cruickshank Patrick Barickman 4/5/05
Geographic Scale -The explicit physical scale of an air quality model affects more abstract levels of scale of data inputs. Atmospheric Chemistry -The dynamic interaction of chemicals and meteorology. Modeling Visibility in the National Parks - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Geographic Scale -The explicit physical scale of an air quality model affects more abstract levels of scale of data inputsAtmospheric Chemistry -The dynamic interaction of chemicals and meteorology
Modeling Visibility in the National Parks -Modeling at the regional scale – Long range transport in addition to chemistry
Using the Results, Dealing With Uncertainty -Modeling complex systems rarely yields definitive results
This image shows a magnified view of aerosol particles collected in the industrial city This image shows a magnified view of aerosol particles collected in the industrial city of Port Talbot, England. Many of the particles measure roughly 2.5 microns across, of Port Talbot, England. Many of the particles measure roughly 2.5 microns across, small enough to easily enter and damage human lungs. (Micrograph adapted fromsmall enough to easily enter and damage human lungs. (Micrograph adapted from Sixth Annual UK Review Meeting on Outdoor and Indoor Air Pollution Research Sixth Annual UK Review Meeting on Outdoor and Indoor Air Pollution Research 15th–16th April 2002 (Web Report W12), Leicester, UK, MRC 15th–16th April 2002 (Web Report W12), Leicester, UK, MRC Institute for Environment and Health)
Chemical transformationChemical transformationof NOof NOxx from Cars/combustion from Cars/combustion
Depending on temperature and humidity Depending on temperature and humidity ammonium nitrate will exist as a:ammonium nitrate will exist as a:1)1) Solid particle (cold and dry)Solid particle (cold and dry)2)2) Aqueous droplet (high humidity)Aqueous droplet (high humidity)3)3) Dissociate into gas (warm)Dissociate into gas (warm)
• • Temperature is warm (> 0Temperature is warm (> 0°° C ) C )
Atmospheric Chemistry ModelingAtmospheric Chemistry ModelingWhat Kind OF Model Should I Use?What Kind OF Model Should I Use?
Cache Valley:Cache Valley:• • Interested in secondary chemistry (90% NHInterested in secondary chemistry (90% NH44NONO33))
- NH- NH33 + HNO + HNO33 NHNH44NONO33
- Model must treat this and “lead-up” chemical reactions- Model must treat this and “lead-up” chemical reactions• • Cache Valley is small and contained. Cache Valley is small and contained. • • Transport by wind is limited. Weather data is limited.Transport by wind is limited. Weather data is limited.• • PMPM2.52.5 concentrations uniform throughout valley. concentrations uniform throughout valley.
What is my goal?:What is my goal?:1)1) Represent average airshed conditions.Represent average airshed conditions.
• • Valley concentrations are uniform.Valley concentrations are uniform. • • Don’t need to tie results to widely spaced monitors.Don’t need to tie results to widely spaced monitors.
2) Test NO2) Test NOxx, VOC, NH, VOC, NH33 control strategies control strategies
• • Basic control strategies are needed.Basic control strategies are needed.
1)1) Complex grid based model.Complex grid based model. • • Gridded emissions, meteorology, chemistry.Gridded emissions, meteorology, chemistry. • • Spatially and temporally oriented.Spatially and temporally oriented.
2) Simple box model.2) Simple box model. • • Single volume, no transport, “shake the box”.Single volume, no transport, “shake the box”. • • Provides average conditions.Provides average conditions.
What Kind OF Model Should I Use?What Kind OF Model Should I Use?
Results can be tied to the Logan monitor.Results can be tied to the Logan monitor.Valley concentrations seem mixed and uniform.Valley concentrations seem mixed and uniform.Valley PMValley PM2.52.5 problem tied to NO problem tied to NOxx, VOC, NH, VOC, NH33 dynamics. dynamics.
Are my emissions reasonable?Are my emissions reasonable?Are my emissions reasonable relative to the box size?Are my emissions reasonable relative to the box size?
Meteorology is measured and hence, fixed.Meteorology is measured and hence, fixed.How does the meteorology impact the chemistry?How does the meteorology impact the chemistry?
Represent the whole valley?Represent the whole valley?Just the populated portion?Just the populated portion?
Do my predictions look reasonable?Do my predictions look reasonable?No? Why not? Try again …No? Why not? Try again …
OO33 progressively increases. progressively increases. OO33 depleted at night. depleted at night.
Some Problems …Some Problems …
Atmospheric Chemistry ModelingAtmospheric Chemistry ModelingWhat Might Explain My Problems?What Might Explain My Problems?
#1 : NO#1 : NO22 appears to be progressively depleted. appears to be progressively depleted.
• • Is our “box” too big relative to emissions coming in?Is our “box” too big relative to emissions coming in?• • Is there too much photochemistry happening – NOIs there too much photochemistry happening – NO22 depletion? depletion?
• • Is the “box” not big enough – too much VOC?Is the “box” not big enough – too much VOC?• • Is the photochemistry happening too quickly?Is the photochemistry happening too quickly?• • What else is increasing to allow OWhat else is increasing to allow O33 to build? to build?
#3 : O#3 : O33 depleted at night. depleted at night.
• • Is there a reaction happening too fast?Is there a reaction happening too fast?• • Does subtle meteorology explain the discrepancy?Does subtle meteorology explain the discrepancy?
• • The model cannot capture the subtleties.The model cannot capture the subtleties.• • I shouldn’t expect to match the observations exactly.I shouldn’t expect to match the observations exactly.• • The model results represent average airshed conditions.The model results represent average airshed conditions.
What Might Explain My Problems?What Might Explain My Problems?
Considering the above: Considering the above:
• • I want my ratios to be reasonable -I want my ratios to be reasonable - NONOxx:NH:NH33, NO:NO, NO:NO22
• • Trends match observations.Trends match observations.• • Does it make sense?Does it make sense?
• • AQ modeling is not a research project – it is applied modeling.AQ modeling is not a research project – it is applied modeling.
What’s the Skinny?What’s the Skinny?
Atmospheric Chemistry ModelingWhat’s the Skinny?What’s the Skinny?
Identify dynamics behind AQ problem.Identify dynamics behind AQ problem.Identify scale of AQ problem.Identify scale of AQ problem.Select model as appropriate to above and goals.Select model as appropriate to above and goals.Understand uncertainty.Understand uncertainty.AQ modeling is not a research project – it is AppliedAQ modeling is not a research project – it is Applied.
Geographic Scale -The explicit physical scale of an air quality model affects more abstract levels of scale of data inputsAtmospheric Chemistry -The dynamic interaction of chemicals and meteorology
Modeling Visibility in the National Parks -Modeling at the regional scale – Long range transport in addition to chemistry
Using the Results, Dealing With Uncertainty -Modeling complex systems rarely yields definitive results
Tyler CruickshankPatrick Barickman
4/5/05
http://www.wrapair.org/
http://coha.dri.edu/index.html
Overall Goal of the Regional Haze Rule (CAA, 1990)
MM5 Modeling at the Continental Scale
Emissions Inventory
What is the model trying to evaluate?
Light Extinction (Bext): The attenuation of light due to scattering and absorption as it passes through a medium Benefit: Light extinction can be directly related to gaseous and aerosol concentrations.Drawback: Light extinction is non-linearly related to a person perception of changes in haze.
How is it done?The model converts concentrations of pollutants into the extinction coefficients These are based on known relationships between the type of particle and its effect on visibility
How is the evaluation made?
http://vista.cira.colostate.edu/views/Observations in the National Parks and Wilderness Areas
Geographic Scale -The explicit physical scale of an air quality model affects more abstract levels of scale of data inputsAtmospheric Chemistry -The dynamic interaction of chemicals and meteorology
Modeling Visibility in the National Parks -Modeling at the regional scale – Long range transport in addition to chemistry
Using the Results, Dealing With Uncertainty -Modeling complex systems rarely yields definitive results
Tyler CruickshankPatrick Barickman
4/5/05
The Weight of Evidence Approach
• The Causes of Haze• Data for each state’s Regional Haze State Implementation Plan (RH SIP)• Sulfates and Nitrates • Uncertainty in the model results require supporting evidence
Two models used•Tagged Species Source Apportionment (TSSA)•Trajectory Regression Attribution Method
Back Trajectory Analysis
Utah Emissions Inventory•S02 + NH3 = SO4
•Nox + NH3 = NH3
Weight of EvidenceThis is a descriptive approach that is narrative and qualitative rather than purely quantitative
Tyler CruickshankPatrick Barickman
4/5/05
Summary
• Complex System – “One not describable by a single rule. Structure exists on many scales… not reducible to only one level of