# Presentation: 187002

## Intercontinental Transport of Aerosols: Implications for Regional Air Quality

**Mian Chin, Paul Ginoux****1****, Thomas Diehl**
**Atmospheric Chemistry and Dynamics Branch**
**NASA Goddard Space Flight Center**
**1****Currently at GFDL**

_**Acknowledgments:**_
**IMPROVE data**
**MODIS data**
**NASA funding**

## Introduction

**Concentration of aerosol particles, also known as particulate matter (PM), is one of the major components that determine ambient air quality**
**While local and regional emission sources are the main cause of air pollution problems, aerosols can be transported on a hemispheric or global scale**

## Introduction (2)

**We use the global model GOCART to answer the following questions:**
**What is the contribution of regional anthropogenic emission to the PM2.5 concentrations over the U.S.?**
**What is the contribution of long-range transport to the surface PM2.5 concentrations over the U.S. ?**
**What is the seasonal variation of the “background” PM2.5?**

| AQI values, categories, and pollutant concentration values for ozone, PM2.5, and PM10 
(source: EPA, http://www.epa.gov/airnow/aqibroch/aqi.html) |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
| AQI | Air Quality | Color Scale | Ozone |  | PM2.5 | PM10 |
|  |  |  | (8 hr ppb)    (1 hr ppb) |  | (μg m-3) | (μg m-3) |
| 0 – 50 | Good | Green | 0 – 64 | - | 0 – 15 | 0 – 54 |
| 51 – 100  | Moderate | Yellow | 65 – 84 | - | 16 – 40 | 55 – 154  |
| 101 – 150  | Unhealthy for sensitive groups | Orange | 85 – 104 | 125 – 164 | 41 – 65 | 155 – 254  |
| 151 – 200 | Unhealthy | Red | 105 – 124 | 165 – 204 | 66 – 150 | 255 – 354 |
| 201 – 300 | Very unhealthy | Purple | 125 – 374 | 205 – 404 | 151 – 250 | 355 – 424 |

## Comparison with the IMPROVE data of surface PM2.5 concentrations

**Model**

**Surface data**

- 200104

- 200109

**PM2.5 composition assumed in the model:**
**Sulfate**
**BC**
**OC**
**Fine mode dust**
**Fine mode sea-salt**

## Surface aerosol concentrations at IMPROVE sites 

- Comparisons of daily average aerosol concentrations at 3 IMPROVE sites for 2001.
- Red circles: IMPROVE data.  Black lines: GOCART model

- Overall comparison of monthly mean PM2.5 concentrations at all IMPROVE sites for 2001

## Model Experiments(for US air quality study)

| Exp. | Definition | Model setup |
| --- | --- | --- |
| ALL | PM2.5 from all sources, including anthropogenic, biomass burning, and natural emissions | Standard model run |
| BKG | Background PM2.5 – from sources we cannot control, e.g. dust, volcanoes, trees, long-range transport from other regions  | Model run without North America anthropogenic emissions |
| NAT | PM2.5 from natural sources only | Model run without all anthropogenic emission |
| NAM
ASA
EUR | Pollution aerosols from North America (NAM), Asia (ASA), or Europe (EUR) anthropogenic emissions | Differences between standard run and the run without anthropogenic emissions in a selected region |
| AFR
ASA
MDE | Dust aerosol from Africa (AFR), Asia (ASA), or Middle East (MDE) | Differences between standard run and the run without emissions in a selected region |

*SU*
*BC*
*OC*

*DU*

## Major Aerosol Source Regions

- Sulfur

- NAM

- EUR

- ASA

- Dust

- AFR

- MDE

- ASA

## Surface PM2.5 Concentrations

- Western:
- About 70% PM2.5 is “background”
- Nearly 60% is “natural” (dust, biogenic aerosols)

- Monthly average surface layer PM2.5 concentrations in 2001 from the GOCART model (see earlier pages for experiment definition).  Annual average concentrations and contributions from different sources are shown.
- ALL – BKG = NAM pollution
- BKG – NAT = pollution from other regions

- Eastern:
- Less than 40% PM2.5 is “background”
- Nearly 1/3 is “natural” (dust, biogenic aerosols)

- Local anthrop.

- Local anthrop.

- Local anthrop.

- Local anthrop.

- Int. anthrop.

- Int. anthrop.

- Int. anthrop.

- Int. anthrop.

- Total natural.

- Total natural.

- Total natural.

- Total natural.

## Surface Sulfate Concentrations

**Surface Sulfate Concentrations**

- Western:
- 70 – 80% sulfate is from NAM local/ regional pollution

- Eastern:
- More than 90% sulfate is from NAM local/ regional pollution

- Monthly average surface layer sulfate concentrations in 2001 from the GOCART model (see earlier pages for experiment definition). Annual average concentrations and contributions from different sources are shown.

## Surface Fine Mode Dust Concentrations

- Monthly average surface layer find mode dust concentrations in 2001 from the GOCART model (see earlier pages for experiment definition). Annual average concentrations and contributions from different sources are shown.

- SW:
- About 60% fine mode dust is “local” (20% Asia, 13% Africa, 5% Middle East

- Eastern:
- About 1/2 fine mode dust is from Asia
- Nearly 30% fine mode dust is from Africa

- NW:
- 1/2 fine mode dust is from Asia, 1/4 from Africa

## Hemispheric Transport – How do the “foreign sources” affect US air quality? (April 2001 as an example)

**Sulfate Over North America:**
**Most sulfate stays in the boundary layer**
**Pollution from Asia can travel around the hemisphere at higher altitudes above BL**
**European pollution makes its way over N. America at higher latitudes**
**In the BL over North America, most sulfate is from is own regional source**

- West Coast

- East Coast

## Hemispheric Transport – How do the “foreign sources” affect US air quality? (April 2001 as an example)

**Dust Over North America:**
**Dust plume has broad vertical extension above the BL**
**Most dust below 6 – 7 km is from Asia**
**Dust from the Middle East contributes to about 10% dust loading**
**African dust is an important contributor to the dust level in the tropics and at high altitudes above 6 – 7 km**

- West Coast

- East Coast

## Conclusions

**Surface PM2.5:**
**Western: **
**30% domestic anthropogenic**
**60% “natural”**
**10% anthropogenic from other continents**
**Eastern: **
**60% domestic anthropogenic**
**30% natural**
**10% anthropogenic from other continents**
**Surface sulfate:**
**Western:**
**70-80% domestic anthropogenic **
**Eastern:**
**90% domestic anthropogenic**
**Surface fine mode dust:**
**Southwestern:**
**60% from local desert**
**Other regions: **
**50% from Asia**
**25-30% from Africa**
**The “background” PM2.5 has large seasonal variations, with the highest values in April-May-June**