HPmag | Magazine | Winter 2007 | Special Report

special report

Dust in the Wind
Tiny specks could have a big effect on your business.

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.

Jason Dunion, a hurricane researcher at the NOAA Atlantic Oceanographic and Meteorological Laboratory’s Hurricane Research Division in Miami, FL, and his colleagues at the University of Wisconsin-Madison, Madison, WI, 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.”

The findings were published in a paper in Geophysical Research Letters in October 2006. 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.

“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.”

RARE SAMPLE
In 2002, Dunion developed a techniques 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.

Last 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.

“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 (see HP, Winter 2003, page 14).

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.