Aerospace Technology Development

Earth's Smoke Viewed From Space

NASA RESEARCHERS CLOSELY MONITORED this year's fires in Mexico, using the unique perspective of space, to see how smoke from natural and human-induced fires contribute to global air pollution and climate changes. Since the beginning of the Mexican fires in late March and early April of this year, NASA atmospheric researchers used the Total Ozone Mapping Spectrometer (TOMS) to observe the smoke aerosols emitted by the fires.

The TOMS instrument has the ability to obtain daily images of the amount of smoke present in any atmospheric conditions anywhere in the world. TOMS makes 35 measurements every eight seconds, each covering 30 to 125 miles wide, from Earth's surface to the atmosphere's top.

Fires such as those in Mexico interest scientists because smoke contributes to the overall regional air pollution levels that can impact the quality of air that humans breathe, especially those with asthma. Increased smoke concentration from human-induced fires could contribute to global climate change.

The current NASA-developed TOMS instrument is a second-generation backscatter ultraviolet ozone sounder. It measures ozone indirectly by comparing ultraviolet light emitted by the Sun to that scattered from Earth's atmosphere back to the satellite at six wavelengths. Backscattered radiation is solar radiation that has penetrated Earth's lower atmosphere and is then scattered by air molecules and clouds back through the stratosphere to the satellite sensors. Along that path, a fraction of the ultraviolet is absorbed by ozone.

By comparing the amount of backscattered radiation to observations of incoming solar energy at identical wavelengths, scientists can calculate Earth's albedo, the ratio of light reflected by Earth compared to that which it receives. Changes in albedo at the selected wavelengths can be used to derive the amount of ozone above the surface.

The fires started in southern Mexico and northern Guatemala near the end of March 1998. Some fires were started as part of the annual clearing of agricultural fields; others started naturally with lightning because of the extremely dry conditions.

The small particles, called aerosols, can affect the amount of energy reaching Earth's surface by reflecting and/or absorbing sunlight. Smoke aerosols also can act as small particles on which clouds can form. Clouds containing smoke aerosols are believed to reflect and absorb energy in different ways than clouds formed from natural particles, such as dust or sea salt.

"Shortly after the fires started, we noticed the huge increase in the amount of aerosols (in this case smoke) in the region," said Dr. Jay R. Herman, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Large amounts of smoke extended into Florida, Texas, New Mexico, California and Wisconsin. On May 16, the smoke plume extended across the eastern United States, passing through Ohio and into southern Canada.

Because of the difficulties in extinguishing the fires, some large smoke plumes are lingering in Mexico. The smoke tends to extend from the ground up to an altitude of about three to four kilometers (1.8 miles) and to follow the prevailing winds. Because of wind shear in this altitude range, there is frequently more than one plume, with smoke blowing from west to east and from south to north.

The fires and accompanying smoke lasted through the middle of June, when rain finally relieved the drought conditions associated with El Niño weather patterns. Since then, there have been major fires observed in Russia and South America, as well as extraordinary amounts of Saharan dust blowing across the Atlantic into the Caribbean and across the southern United States and Mexico.

TOMS is part of NASA's Earth Science Enterprise, a long-term, coordinated research effort to study Earth as a global system. The TOMS program is managed by the Goddard Space Flight Center for NASA's Office of Earth Science in Washington, D.C.

For more information, contact Dr. Jay R. Herman at Goddard Space Flight Center.
Call: 301/286-7821, E-mail: Herman@TPARTY.gsfc.nasa.gov Please mention you read about it in Innovation.

Using the TOMS instrument, scientists can obtain images of atmospheric smoke present anywhere in the world. Increased smoke contributes to global climate change.