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TINY DUST SPECKS COULD HAVE BIG EFFECT ON HURRICANES

Satellite image of Saharan Air Layer outbreak moving over Africa on March 3, 2004, where vast amounts of Saharan dust clearly can be seen from space.Oct. 13, 2006 Never underestimate the power of something small. Researchers are finding that Saharan dust storms containing tiny specks of dust are linked to suppressed hurricane activity in the Atlantic. (Click satellite image for larger view of Saharan Air Layer outbreak moving over Africa on March 3, 2004, where vast amounts of Saharan dust clearly can be seen from space. Click here for high resolution version. Image courtesy of NASA.)

Jason Dunion, a hurricane researcher at the NOAA Atlantic Oceanographic and Meteorological Laboratory's Hurricane Research Division in Miami, Fla., and his colleagues at the University of Wisconsin-Madison, studied the past 25 years of satellite data. They found that during times of intense hurricane activity, the large clouds of dust that periodically blow westward from the Saharan Desert are relatively scarce. In years when there were fewer hurricanes, the dust storms were stronger and tended to spread over much of the Atlantic and Caribbean Sea.

"The research conducted by Dunion and his colleagues is improving our understanding of hurricanes and what affects their behavior," said retired Navy Vice Adm. Conrad Lautenbacher, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator. "This is another example of how NOAA's research provides value to society. This work will provide another data point used to make better forecasts and warnings, which translates into saving lives and protecting property."

Satellite image of Saharan Air Layer outbreak moving off of Africa into the North Atlantic on March 2, 2003, where vast amounts of Saharan dust can be seen as captured by the MODIS instrument aboard NASA's Terra satellite.The findings were published in a paper in Geophysical Research Letters this week. The lead author is Amato Evan of the University of Wisconsin-Madison. Dunion said the work is a piece of a larger puzzle, where researchers are trying to understand how the various components of these dust storms—dry air, strong winds and suspended dust—can act to suppress hurricane formation and intensification. (Click satellite image for larger view of Saharan Air Layer outbreak moving off of Africa into the North Atlantic on March 2, 2003, where vast amounts of Saharan dust can be seen as captured by the MODIS instrument aboard NASA's Terra satellite. Click here for high resolution version. Image courtesy of NASA.)

"This research is still in its infancy, but the results of this most recent study are very encouraging," Dunion said. It represents the first long-term analysis of the relationship between Saharan dust storms and hurricanes and supports our previous hypotheses that these dust storms tend to suppress hurricane formation."

In 2002, Dunion developed a technique for detecting the large dust clouds using special infrared imagery from the NOAA GOES satellites. Since then, Dunion and his colleagues have been looking at the large dust clouds and their possible effect on hurricanes.

This summer, Dunion led the NOAA Hurricane Research Division's aircraft field program conducted under the NOAA Intensity Forecasting Experiment, or IFEX, and spearheaded NOAA's participation in the NASA African Monsoon Multidisciplinary Analyses, a field campaign designed to look at Saharan dust storms and tropical cyclone formation in the eastern and central Atlantic.

"This summer, we were able to focus our efforts over a part of the ocean basin that is rarely sampled by aircraft and yet is a breeding ground for hurricane seedlings that account for over half of the tropical storms and hurricanes that we see in the Atlantic each year," Dunion said. "This research has helped us learn more about what causes hurricanes to intensify or weaken."

Part of the field work carried out this summer was Dunion's Saharan Air Layer Experiment, or SALEX, that used NOAA's P-3 Orion turboprop plane and G-IV high altitude jet to study the interactions between tropical cyclones and Saharan dust storms. Both aircraft are routinely used in NOAA's hurricane hunter activities.

Eight SALEX missions were flown during the peak of the dust storm activity this year. These Saharan dust storms are part of a feature called the Saharan Air Layer (SAL). SAL outbreaks tend to be most intense in the early summer and are responsible for ejecting vast amounts of dry, dusty air into the Atlantic throughout the hurricane season.

Dunion noted that the size of the dust storms can cover an area roughly the size of the lower 48 U.S. states and can often travel as far west as Central America, the Gulf of Mexico and South Florida.

Data collected during the 2006 Atlantic hurricane season will be incorporated into NOAA and other operational forecast models to help improve forecasts of hurricane track and intensity.

In 2007 NOAA, an agency of the U.S. Commerce Department, celebrates 200 years of science and service to the nation. Starting with the establishment of the U.S. Coast and Geodetic Survey in 1807 by Thomas Jefferson much of America's scientific heritage is rooted in NOAA. The agency is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and information service delivery for transportation, and by providing environmental stewardship of the nation's coastal and marine resources. Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners, more than 60 countries and the European Commission to develop a global monitoring network that is as integrated as the planet it observes, predicts and protects.

Relevant Web Sites
NOAA Saharan Air Layer Experiment

NOAA Hurricane Research Division

NOAA Atlantic Oceanographic and Meteorological Laboratory

Media Contact:
Jana Goldman, NOAA Research, (301) 713-2483 ext. 181