# Presentation: 608287

## Why Forecast Air Quality?

- Protect public health
- Allows the public to plan activities that avoid exposure
- Allows sensitive individuals to plan activities and healthcare
- Effectively run a voluntary emissions reduction program
- Participation depends on forecast accuracy and timeliness
- Affects the public’s activities
- Affects sponsor or donor agency support
- Conduct special sampling
- Allows sufficient time to prepare monitoring equipment and personnel
- Lets researchers sample pre-episode conditions

## Short Course on Air Quality Forecasting

- Introduction, p. 5
- Meteorology and Air Quality, p. 29
- Meteorological Products and Examples, p. 55
- Case Studies, p. 102
- Air Quality Forecasting Tools, p. 121
- Developing a Forecasting Program, p. 141
- Daily Forecast Operations, p. 171
- Appendix: Useful Weather and Air Quality Links
- Contest

## Course Objectives

- Understand the meteorological processes that affect pollution concentrations
- Learn more about meteorological and air quality forecasting products
- Learn how to use and evaluate meteorological forecast data (case studies)
- Discuss the tools available for air quality forecasting
- Discuss how to develop, operate, and maintain a forecasting program

## Forecasting Programs

- The Process of Developing, Operating, and Improving an Air Quality Forecasting Program

- Need for an
- AQ Forecast

- Develop
- a Program

- Operate
- the Program

- Revise
- the Program

- Data
- Collection

- Forecast
- Preparation

- Forecast
- Communication

## What’s New in This Year’s Course

- Includes a different pollutant
- PM2.5
- Year-round pollutant forecasting
- Has more instructors
- From different areas of the country
- Range of skills and backgrounds
- Incorporates comments from last year’s course
- Provides more examples and applications

## Short Course – Design Goals

**Focus.**  Forecasting air quality—both PM2.5 and ozone concentrations.  The approach applies to other pollutants.
**Practical.**  Beyond theory, the course contains practical advice and reference to examples, tools, and methods.
**Gateway.**  The course workbook is a gateway to additional resources.
**Evolving. ** It will improve in time through your feedback.

## Forecasting Philosophy (1 of 3)

- More forecasting tools = better results
- No “silver bullet”
- Several tools provide a consensus forecast
- Understand how the system works
- Determine how meteorological processes influence air pollution in your area
- Forecast the processes that affect air quality, then predict the air quality

## Predicting weather (and air quality) requires examining information for several different spatial and time scales.
Global
	Space: 4,000 km – 20,000 km
	Time : 1 - 2 weeks 

Synoptic
	Space: 400 km – 4,000 km
	Time: 1 day – 1 week

Mesoscale
	Space: 10 km – 400 km
	Time: 1 hr – 1 day

Urban
	Space: 5 km - 50 km
	Time: 1 hr  - 4 hr

Neighborhood
	Space: 500 m - 5 km
	Time: 1 min – 1 hr

**Global**
- 	Space: 4,000 km – 20,000 km
- 	Time : 1 - 2 weeks
**Synoptic**
- 	Space: 400 km – 4,000 km
- 	Time: 1 day – 1 week
**Mesoscale**
- 	Space: 10 km – 400 km
- 	Time: 1 hr – 1 day
**Urban**
- 	Space: 5 km - 50 km
- 	Time: 1 hr  - 4 hr
**Neighborhood**
- 	Space: 500 m - 5 km
- 	Time: 1 min – 1 hr

- Forecasting Philosophy (2 of 3)

## Forecasting Philosophy (3 of 3)

- Forecasting Process

- Predict weather

- Predict weather’s effect on emissions and chemistry

- Estimate AQ concentration

- Convert to AQI

**Notes:**
Mention emission versus chemistry example.

Cold=wood burn=more emissions

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

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

- Air Quality Background – Types

## Air Quality Background – 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 |

## Ozone – Chemistry

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

-    NO + O3  NO2 + O2       Destruction

**Notes:**
Complicated
Prod
Dest
Titration

## PM – Sources and Chemistry

- Particulate matter (PM) is a complex mixture of solid and liquid particles that vary in size and composition.
- Size of PM
- Sources
- Composition
- Seasonal and regional differences
- Unusual events
- Formation processes

## PM – Size (1 of 2)

- Size of PM
- Particle sizes (0.005 to 100 μm)
- Ultrafine Particles (<0.1 μm)
- Fine Particles (0.1 and 2.5 μm)
- Coarse Particles (> 2.5 μm)

- Human Hair (70 μm diameter)

- Human hair cross section (70 μm)

- PM2.5
- (2.5 μm)

- PM10
- (10 μm)

- M. Lipsett, California Office of Environmental Health Hazard Assessment

## PM – Size (2 of 2)

- Adapted from
- Husar (1999)

| Name | Ultrafine | Fine (PM2.5) | Coarse (PM10) |
| --- | --- | --- | --- |
| Particle size | very small | small | larger |
| No. of particles | most | moderate | least |
| Amt. of mass | small | moderate | most |
| Residence time | days-week | week-month | hours-day |
| Removal process | coagulation | condensation | sedimentation |

## PM – Sources

- Primary PM (directly emitted):
- Suspended dust
- Sea salt
- Organic carbon
- Elemental carbon
- Metals from combustion
- Small amounts of sulfate and nitrate

- Secondary PM (gases that form PM in the atmosphere):
- Sulfur dioxide (SO2): forms sulfates
- Nitrogen oxides (NOx): forms nitrates
- Ammonia (NH3): forms ammonium compounds
- Volatile organic compounds (VOC): forms organic carbon compounds

- PM is composed of a mixture of primary and secondary compounds.

## NaCl – salt is found in PM near sea coasts and after de-icing materials are applied.
Organic Carbon (OC) – consists of hundreds of separate compounds containing mainly carbon, hydrogen, and oxygen. 
Elemental Carbon (EC) – composed of carbon without much hydrocarbon or oxygen.  EC is black, often called soot.  
Liquid Water – soluble nitrates, sulfates, ammonium, sodium, other inorganic ions, and some organic material absorb water vapor from the atmosphere.

**Organic Carbon (OC) –** consists of hundreds of separate compounds containing mainly carbon, hydrogen, and oxygen.
**Elemental Carbon (EC) – **composed of carbon without much hydrocarbon or oxygen.  EC is black, often called soot.
**Liquid Water** **–** soluble nitrates, sulfates, ammonium, sodium, other inorganic ions, and some organic material absorb water vapor from the atmosphere.

- PM2.5 Composition

- Chow and Watson (1997)

**Geological Material –** suspended dust consists mainly of oxides of Al, Si, Ca, Ti, Fe, and other metal oxides.
**Sulfate** **–** results from conversion of SO2 gas to sulfate-containing particles.
**Nitrate** **–** results from a reversible gas/particle equilibrium between ammonia  (NH3), nitric acid (HNO3), and particulate ammonium nitrate.
**Ammonium** **–** ammonium bisulfate, sulfate, and nitrate are most common.

- Most PM mass in urban and nonurban areas is composed of a combination of the following chemical components:

## PM2.5 – Spatial Patterns

- From Solomon and Scheffe (2002)

## PM2.5 – Seasonal Patterns

- Falke (1999)

## PM2.5 – Unusual Events

- Unusual PM Events
- Agricultural burning - farming byproducts (rice straw, orchard prunings, etc.)
- Wildland fires - 100 to 1000+ acres (biomass: trees, shrubs, grasses, etc.)
- Windblown dust
- Locally generated airborne dust from winds blowing across agricultural or barren land
- Global as winds can carry aerosols for weeks and over 1000’s of kilometers

*See Appendix for Internet links.*

## PM – Unusual Events

- February 26, 2000

- July 7, 2002 at 1115 EST

- http://seawifs.gsfc.nasa.gov/SEAWIFS/HTML/dust.html

## PM – Formation Processes

- February 2002

- Short Course on Air Quality Forecasting: Introduction

## PM – Formation Processes

|  | Winds | Clouds, fog | Winds | Temperature |
| --- | --- | --- | --- | --- |
|  | Temperature | Temperature | Precipitation | Relative humidity |
|  | Solar radiation | Relative humidity |  | Winds |
|  | Vertical mixing | Solar radiation |  |  |
|  |  |  |  |  |

***Meteorological Processes***

## Summary

- Ozone is a secondary pollutant formed from emissions (NOx and VOC).  It is most prevalent in the summer.
- PM2.5 consists of numerous types of solid and liquid particles that are directly emitted (primary) or formed in the atmosphere (secondary).  High concentrations occur year round.
- Forecasting air quality requires an understanding of the processes that produce pollution.

- Next step - Meteorology and Air Quality
- Questions