# Presentation: 126404

## Intercontinental transport of pollution and dust aerosols: Implications for air quality

**Mian Chin, Thomas Diehl, Paul Ginoux**

## Transport of aerosols from satellite and model

- Figure from Yoram Kaufman and Reto Stöckli

- MODIS (Satellite)

- GOCART (Model)

## Yoram’s suggestions/comments on the MODIS-GOCART movie

- “It would be nice to try and show both the optical thickness and
- the fact that AOT may be mainly coarse or fine in one movie. E.g. using a two dimensional color bar, that starts from blue for no aerosol, but reaches dark green for high AOT if the coarse AOT is more than 60%, or dark red (the present one) if the fine AOT is more than 60%.”
- – **Yoram’s suggestion to Reto Stockli & Dave Herring on the figures, February 2002**

- “The aerosol movie is of great importance, far beyond the outreach goal. It may become the highlight of the aerosol research community looking for new ideas.....As a proof, let me mention that I got a full hearted compliment from Ralph Kahn.”
**– ****Yoram, on the MODIS GOCART movie, February 2002**

## Yoram’s comments on GOCART model

- “General conclusions:
- GOCART is doing remarkably well for most locations... Based on these results, we may be close to a situation that an aerosol model driven/improved by AERONET can replace MODIS or measurements of aerosol that do not include polarization. Thus we are ready for more accurate space measurements.”
**– ****Yoram, after comparing MODIS, AERONET, and GOCART, September 2002**

## Yoram’s work on using satellite data and model to estimate transport, deposition, and anthropogenic aerosol forcing –

## Yoram’s work on using data and model to estimate anthropogenic aerosol fraction

- Yoram’s method to estimate anthropogenic aerosol optical thickness (Kaufman et al., GRL 2005):
- Whereτ, τa and τm are total, anthropogenic, and maritime aerosol optical thickness
- fτ, fd, fm, fa are fractions of fine mode, dust, maritime, and anthropogenic aerosol optical thicknesses

- Kaufman et al., GRL, 2005

## Yoram’s work on using data and model to estimate dust transport and deposition

- Dust deposition rate (Tg/mon) over the Atlantic between 0° – 40°N (Kaufman et al., JGR 2005)

- Kaufman et al., JGR, 2005

## As for air quality, we have to deal with the surface fine mode aerosol concentrations

## Can we derive surface PM information from the column AOD?

**Can we derive surface PM information from the column AOD?**

- (Figures from Al-Saadi et al., BAMS 2005)

- Red circle: MODIS AOD   Black: EPA PM2.5

-  – Maybe, since they seem to track with each other

## Can we derive surface PM information from the column AOD?

- Engel-Cox et al. (2004) show that the correlation coefficients between the MODIS AOD and surface PM2.5 measurements vary with locations: better correlated in the eastern US than in the western US for the period of 4/1 – 9/30/2002.

-  – Maybe not, since they don’t always track with each other

## Why the relationship between AOD and PM2.5 changes with location and time?

- Quantitative link between column AOD and surface PM2.5 critically depends on knowledge of aerosol _**vertical profile**_ and _**composition**_ !!!  Both have large spatial and temporal variations especially in the western U.S.

- (Chin et al., “*Possibilities and challenges in using satellite aerosol optical depth data for surface air quality studies*”, manuscript in preparation)

## Model study of impact of emission and transport on surface air quality 

- Comparisons GOCART model simulated surface fine aerosol concentrations over the U.S. with the IMPROVE measurement data (for the year 2001)
- Analysis of the origin of surface fine aerosol over the U.S. – Where are they from?
- Intercontinental transport of aerosols in a hemispheric scale – How does one region impact another?

## Emission in 2001

- Sulfur emission from pollution sources (TgS/yr):
- World – 64.9
- Asia – 26.3
- Europe – 17.3
- North America – 12.3
- (3 regions emit 85% of global total pollution)

- Dust emissions (Tg/yr):
- World – 2773
- Eastern Asia – 566
- Middle East – 443
- Northern Africa – 1609
- (3 regions emit >90% of global total)

## Surface aerosol concentrations over the U.S.

- IMPROVE network measurements:
- Initiated in 1985 by EPA, NPS, USDA, etc.
- Measuring sulfate, nitrate, ammonia, BC, OC, salt, mineral elements, and many other species
- Reporting PM2.5, PM10, and RCFM (reconstructed fine mass = (NH4)2SO4 + OM + BC + DUf, which is PM2.5 – nitrate)
- We will use the quantity of RCFM in this work

## IMPROVE sites (142 in 2001)

- We divide the U.S. into four quad-rants: NW, SW, NE, SE

## Daily variations of RCFM and its components.  Line: data  Dots: model

**Daily variations of RCFM and its components.  Line: data  Dots: model**

## Daily variations of RCFM and its components.  Line: data  Dots: model

## Comparison of RCFM (mon avg):

- Remember that all models are wrong; the practical question is how wrong do they have to be to not be useful.
- – Box and Draper, *Empirical Model-Building*, p. 74, 1987

## Compositions of fine aerosol

- Western U.S.:
- Dust, carbonaceous, and ammonium sulfate have similar magnitudes
- Dust peaks in spring, OM peaks in summer
- Eastern U.S.:
- Ammonium sulfate dominates
- Seasonal cycle:
- Sulfate small
- DU large
- OM in the NW large
- Concentrations:
- NW lowest
- SE highest

## Origin of fine aerosol over the U.S.

**North America pollution **

## Origin of fine aerosol over the U.S.

**North America pollution **
**+ biomass burning**

## Origin of fine aerosol over the U.S.

**North America pollution **
**+ biomass burning**
**+ biogenic**

## Origin of fine aerosol over the U.S.

**North America pollution **
**+ biomass burning**
**+ biogenic**
**+**
**local fine dust**
**=**
**Total local RCFM**

## Origin of fine aerosol over the U.S.

**North America pollution **
**+ biomass burning**
**+ biogenic**
**+**
**local fine dust**
**+**
**imported fine dust**

## Origin of fine aerosol over the U.S.

**Red: local pollution (may control)    ****Other: background (hard to control)**

- _RCFM origin:_
- North America pollution (NAM):
- Western 30-40%
- Eastern 65-70%
- Pollution import (TAP):
- Western 2-6%
- Eastern 2-4%
- Dust import (TDUf):
- Western 15-24%
- Eastern 7-9%
- Total import (TDUf+TAP):
- Western 20-30%
- Eastern 9-14%
- Max. in Spring

**North America pollution **
**+ biomass burning**
**+ biogenic**
**+ **
**local fine dust**
**+**
**imported dust**
**+ imported pollution**

## Hemispheric influence of intercontinental transport

## Intercontinental transport of pollution – (NH4)2SO4 as a surrogate

- Asia:
- Eastward transport, efficient removal during transport
- 0.1-0.2 μg/m3 to W.US and N.Afr, more to E.Afr and E.Eur
- < 10% increase to all continents

- Europe:
- Pollution widely spread
- Largest impact on N. Africa with 0.5-5 μg/m3 increase
- 0.2-0.5 μg/m3 to E.Asia

- North America: Relatively regionalized
- Amount to N.Africa/Saudi = Amount from Asia to W.US

## Intercontinental transport of fine dust

- Asia:
- Efficient eastward transport, less removal than sulfate during transport
- 0.2-0.5 ug/m3 to US, N.Afr, MidE, more to E.Afr and E.Eur
- 50% over Arctic
- Widespread in NH

- Middle East:
- Limited effects, mostly to neighbors
- Largest impact on N. Indian O.
- 0.2-0.5 ug/m3 to E.Asia!

- Africa:
- Westward to C.Am, northward to Europe, eastward to Asia-Pacific-......-North America!!

## Summary and conclusions

- Column AOD and surface PM2.5:
- Their relationship varies with location and time, depending on vertical profile and composition of aerosols
- Regional air quality:
- Pollution region is mostly responsible for its own particle air quality
- Intercontinental transport of pollutants:
- Europe has the largest “impact potential over land”
- Asian pollution impact on North America is ... “not much”
- Intercontinental transport of dust:
- Asian dust has the largest “impact potential over land”
- African dust is most intense and can travel around globe

## 2005 “Oscar” (Cimel) winners and the selection committee

- (at the Annual Goddard Aerosol Science Update, 2005)