May 3, 2004 NASA Satellites and Balloons Catch the Fast Pollution “Train” NASA scientists discovered pollution could catch an airborne “express train,” or wind current, from Asia all the way to the southern Atlantic Ocean. Scientists believe during certain seasons, as much as half of the ozone pollution above the Atlantic Ocean may be speeding down a “train” track of air from the Indian Ocean. As it rolls along, it picks up more smog from air peppered with thunderstorms that bring it up from the Earth’s surface. Bob Chatfield, a scientist at NASA’s Ames Research Center, Moffett Field, Calif. said, “Man-made pollution from Asia can flow southward, get caught up into clouds, and then move steadily and rapidly westward across Africa and the Atlantic, reaching as far as Brazil.” Chatfield and Anne Thompson, a scientist at NASA’s Goddard Spaceflight Center, Greenbelt, Md., used data from two satellites and a series of balloon-borne sensors to spot situations when near-surface smog could “catch the train” westward several times annually from January to April. During those periods of exceptionally high ozone in the South Atlantic, especially during late winter, researchers noticed Indian Ocean pollution follows a similar westward route, wafted by winds in the upper air. They found the pollution eventually piles up in the South Atlantic. “We’ve always had some difficulty explaining all that ozone,” Thompson admitted. Seasonal episodes of unusually high ozone levels over the South Atlantic seem to begin with pollution sources thousands of miles away in southern Asia,” Chatfield said. Winds are known to transport ozone and pollutants thousands of miles away from their original sources. Clearly defined individual layers of ozone in the tropical South Atlantic were traced to lightning sources over nearby continents. In addition to ozone peaks associated with lightning, high levels of ozone pollution came from those spots in the Sahel area of North Africa where vegetation burned. However, even outside these areas, there was extra ozone pollution brought by the Asian “express train.” The scientists pinpointed these using the joint NASA-Japan Tropical Rainfall Measuring Mission satellite to see fires and lightning strikes, both of which promote ozone in the lower atmosphere. Researchers also identified large areas of ozone smog moving high over Africa using the Total Ozone Mapping Spectrometer satellite instrument. The scientists confirmed the movement of the smog by using sensors on balloons in the Southern Hemisphere Additional Ozonesondes (SHADOZ) network. A computer model helped track the ozone train seen along the way by the SHADOZ balloon and satellite sensors. The scientists recreated the movement of the ozone from the Indian Ocean region to the Southern Atlantic Ocean. Their research results appear in an article in a recent issue of the American Geophysical Union’s Geophysical Research Letters. The mission of NASA’s Earth Science Enterprise is to develop a scientific understanding of the Earth system and its response to natural or human-induced changes to enable improved prediction capability for climate, weather, and natural hazards. ###
Contacts: Gretchen Cook-Anderson
Headquarters, Washington
Phone: 202/358-0836 Rob Gutro
Goddard Space Flight Center,
Greenbelt, Md.
Phone: 301/286-4044 Mike Mewhinney
Ames Research Center,
Moffett Field, Calif.
Phone: 650/604-3937 Harvey Leifert
American Geophysical Union
Phone: 202/777-7507 | |
Riding the Pollution Train
The red arrows on this globe trace the fast track of ozone pollution from Asia as it contributes to the highest ozone episodes found in the South Atlantic. Asian smog with moderate amounts of ozone moves south into the Indian Ocean. Repeatedly, every few weeks, when this ozone can be swept upwards by tall rainclouds, it can then move eastward rapidly across Central Africa (upper arrow). The long red path is shown to end at Ascension Island, but actually a large patch of ozone fills much of the South Atlantic. Additionally, lightning and vegetation burning over Africa could add highly visible ”pollution peak” features, but these obvious nearby African sources tell only half the story of the Atlantic ozone episodes. CREDIT: NASA, MODIS image 
NASA Sensors Find Pollution Hiding in the SHADOZ of the Atlantic Ocean
Scientists from NASA and 10 tropical countries used balloon-borne ozonesonde sensors in the SHADOZ (Southern Hemisphere Additional Ozonesondes) Project, and found that ozone ”piles up” over the south Atlantic Ocean due to natural circulation patterns and that pollution (low-level ozone) from Africa and South America streams into the pile-up region, making the ozone even more concentrated. This graphic shows how pollution can move with winds blowing from South America pushing pollution into the middle Atlantic, and easterly winds from Africa also blowing pollution into the mid-Atlantic, where atmospheric motions are already dumping ozone. In fact, these easterly winds derive ozone from much further away, in the Central Indian Ocean. The winds do vary in time, corresponding to weather patterns in Africa and its neighboring oceans. CREDIT: NASA GSFC, Barbara Summey 
Pollution Event Spans Nearly One-Third of the Globe
Upper Image: This image from NASA’s TRMM satellite shows the pathway (blue line) of an ozone pollution event, from its origins in Asia. Along the way it passes through regions of lightning. Lightning is associated with natural increases in ozone values in the upper air. The intensity of strikes is coded with colored dots (cool to warm ”intense” values) which appear mostly over South America and Central Africa, Wind streamlines at 25,000 feet are also depicted by the circular and wavy lines. The combination of natural lightning-enhanced ozone with air pollution from Asia is reflected by the ”hot” red- and yellow-colored features in the center of the lower ozone map.
Lower Image: The orange swath in the lower map indicates an extended plume of ozone pollution detected by the TOMS instrument. High levels of ozone pollution extend from South Asia all the way to the coast of Brazil. Some ozone is also formed in South America and Africa, due to lightning and burning. CREDIT: NASA Ames/MSFC/GSFC 
An Ozonesonde and Balloon
Anne Thompson (NASA, left) and Agnes Phahlane (South African Weather Service, right) prepare to launch a balloon carrying an ozonesonde, a sensor that measures ozone. CREDIT: NASA |
