# Presentation: 359842

## Air Quality and Meteorology

- OVERVIEW
- Air Quality
- Emissions
- Chemistry
- Characterization

- Meteorology
- Basic weather patterns
- Temperature (surface/aloft)
- Winds (surface/aloft)
- Transport
- Clouds
- Review of key features

## 	Primary - emitted directly from source
	Secondary - formed in atmosphere 
                         from reaction of primary  
                         pollutants
   Precursors - primary pollutants that 		                form secondary pollutants

- 	Secondary - formed in atmosphere
-                          from reaction of primary
-                          pollutants
-    Precursors - primary pollutants that 		                form secondary pollutants

- Air Quality – Types

## Air Quality – Major Pollutants

| Pollutant | Abbreviation | Type |
| --- | --- | --- |
| Carbon Monoxide | CO | Primary |
| Sulfur Dioxide | SO2 | Primary |
| Ozone | O3 | Secondary |
| Nitrogen Dioxide | NO2 | Secondary |
| Hydrocarbon Compounds | HC | Primary & Secondary |
| Particulate Matter | PM | Primary & Secondary |

## Air Quality – Emissions

- Man-made sources
- NOx through combustion
- VOCs through combustion and numerous other sources
- SO2 through combustion of coal and oil that contains sulfur
- Natural sources (biogenic)
- VOCs from trees/vegetation
- NOx from soils (Midwest fertilizer)
- Concentration depends on
- Source location, density, and strength
- Meteorology

**Notes:**
Add evaporation and biogenics fn of temperature

## Air Quality – Emissions

- Key processes
- Source location, density, and strength
- Dispersion (horizontal mixing) - wind speed
- Vertical mixing - inversion

- Concentration  S/WS

- Wind speed (WS)

- S

**Notes:**
Dispersion is 3d,
Hoziz and vertical
We will classify horizontal dispersion just as dispersion
Vertical mixing is basically vertical dispersion

## Air Quality – Chemistry

- Simplified view of ozone chemistry
- NO2 + O2 + Sunlight  O3	Production

-    NO + O3  NO2 + O2       Destruction

**Notes:**
Complicated
Prod
Dest
Titration

## Air Quality – Meteorology Key Processes

- Meteorology key processes
- Dispersion (horizontal mixing)
- Vertical mixing
- Sunlight
- Transport
- Variations by
- Weather pattern
- Geography
- Diurnal
- Season

**Notes:**
Discussed first three
dispersion, vertical mixing, and sunlight produce
but transport moves around.
Transport - winds move pollutants around

## Air Quality – Urban Site

- Hourly ozone concentrations on July 23, 2001, at an urban site in Nashville, Tennessee

- Emissions				
- Dispersion			 	
- Vertical mixing				
- Sunlight		 	
- Transport				

-      Net            Ozone             Net
- Production       Peak        Destruction

- Precursor
- Accumulation

## Air Quality – Rural and Downwind

- Hourly ozone concentrations on May 22, 2001, at rural downwind site in Grass Valley (Sacramento), California

- Emissions
- Dispersion		
- Vertical mixing		
- Sunlight		
- Transport		

- Background                      Production / Transport

## Air Quality – High Altitude

- Hourly ozone concentrations on May 23, 2001, at a high-altitude site at Fry Pan, North Carolina

- Emissions
- Dispersion
- Vertical mixing	
- Sunlight
- Transport	

- Background Concentrations

## Air Quality – Characterization 

- Examine long-term trends for changes in
- number of high days
- location of peaks

## Air Quality – Characterization 

- Examine seasonal trends

- Average AQI days for PM2.5 in Salt Lake City, Utah (1999-2001)

## Air Quality – Characterization

- Examine day-of-week relationships

- 8-hr ozone exceedances by day of week in Columbus, Ohio (1996-2000)

## Air Quality – Characterization

- Length of 8-hr episodes that occurred in the Northeast U.S. during 1993 to 1997. Most episodes are one-day long; however, most exceedance days occur within episodes that are two days or longer. Seventy-eight percent of 8-hr exceedance days occur in 8-hr episodes that are two days or longer.

- Length of 8-hr Ozone Episodes in the Northeast U.S. (1993-1997)

**   **Examine length of episodes

## Air Quality – Characterization

- Contour plot of the average number of 8-hr site exceedances per year from 1993 to 1997.  The contour lines are drawn for every two days (Dye et al., 1998).

## Air Quality – Characterization

- Evaluating monitoring sites
- Representativeness
- street
- neighborhood
- urban
- background
- downwind
- Local terrain
- Proximity to emissions

**Notes:**
Discuss 3 sites
Important because of stronger winds = peak further downwind 

## Air Quality – Characterization

- Monitoring Sites

## Summary

- Forecasting air quality requires an understanding of the processes that produce pollution:
- 	Emissions
- 	Sunlight
- 	Dispersion
- 	Vertical mixing
- 	Transport

- Next Steps
- Review of Meteorological Processes
- Questions