Air Pollution as a Climate Forcing: A Workshop
Day 2 Presentations
From Regional Emission to Global Atmospheric Loading: Intercontinental Transport of Aerosols in the Context of ACE-Asia
Mian Chin*+ and Paul Ginoux+°
* School of Atmospheric Sciences, Georgia Tech
+ Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, MD, U.S.A.
° GEST, University of Maryland at Baltimore County, Baltimore, MD, U.S.A.
In Spring 2001 (end of March to early May), the intensive field operation of Aerosol Characterization Experiment-Asia (ACE-Asia) was conducted in the western Pacific downwind of Asia. The primary objective of ACE-Asia was to understand the climate and radiative effects of the Asian pollution and dust aerosols on western Pacific Ocean during the season when the outflux from Asian to the Pacific was at its maximum. During ACE-Asia field experiments, high concentrations of pollutants and dust were observed frequently over the western Pacific, and sometimes they reportedly reach North America by long-range transport. To understand the origin of the pollution and dust aerosols over the Pacific and to assess the regional to global scale impact of these aerosols, we use the Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model to analyze the origin of the aerosols. We label the sulfate origins from three major anthropogenic source regions of North America (NAM), Europe (EUR), and Asia (ASA), and label the dust emitted from three major source regions from Africa (AFR), Middle East (MID), and Taklimaken/Gobi desert (ASA). Figure 1 shows the emission rates of sulfur and dust in April 2001 and the borders of the labeled source regions.
We then estimate the relative contributions of sulfate (as pollution aerosol) and dust from different major source regions from the model results with labeled regional emissions (Figure 2). We have found from the model results:
- Intercontinental transport redistributes aerosols from their source regions to other regions and to the global atmosphere. In April, 40-80 % of sulfate over northern Asia was from Europe, and 40-80% of dust over western Asia was from Africa.
- Over the large Pacific Ocean, Asian emissions are the most important sources of pollution and dust aerosols, but pollution from Europe and dust from Africa were also significant contributors.
- During April 2001, about 30-40% and 20-30% of sulfate over the west coast of North America were from anthropogenic sources in Asia and Europe, respectively.
- At the same location and time, about 50-60% and 20-40% of dust were from Taklimaken/Gobi and Africa, respectively.