Dust Affects the North Atlantic
Instruments aboard NASA’S terra satellite have provided evidence that the chilling effect of dust was responsible for one-third of the drop in north Atlantic sea surface temperatures between June 2005 and 2006. The difference in hurricane activity between the two seasons was probably due to this fact. Hurricanes are fueled by heat from warm ocean surfaces leading to stronger and more frequent storms.
However, during the 2006 hurricane season, sea temperatures in the North Atlantic remained quite cool and the season saw only five hurricanes, compared to 15 in 2005 when the ocean surface was warmer. Airborne Saharan dust over the Atlantic was probably responsible for much of the temperature drop and it effectively blocked out the sunlight which never reached the ocean’s surface.
This study was done by William Lou and Kyu-Myong Kim at NASA’s Goddard Space Flight Center , Greenbelt , Maryland . Their research also showed that dust accounted for 30% to 40% of the drop in sea surface temperature between June 2005 and 2006. These findings were reported in the American Geophysical Union’s Geophysical Research letters. They provide the first quantitative estimate of dust’s role in cooling the entire North Atlantic and shows that dust is a potentially important influence on hurricane activities.
In earlier research publications, Lau had first said that Saharan dust blocked sunlight as it blew from the west over the Atlantic so that it never reached the ocean. This caused the ocean surface to cool and led 2006 to be a much weaker hurricane season as compared to 2005. Controversy entered the research and scientists questioned the extent of dust’s influence on the temperature shifts as compared to the influence on El Nino. Lau stated, “Previous studies have looked at how hot, dry air associated with a Saharan dust outbreak affects an individual storm, but our study is the first to focus on dust’s radiative(?) effect on sea surface temperatures, which may affect storms for the entire season. Nobody has suggested that link before.”
Lou and Kim calculated the cooling pattern that Saharan dust should produce on sea surface temperatures from the sun-blocking effect to and compared the results to observe temperature patterns. This study allowed for investigation to show the dust and sea surface temperature link. Data was first collected by the NASA team from the national Center for Environmental Prediction to find out how much solar energy enters Earth’s atmosphere and reaches Earth’s surface free from the influence of dust. However, not all of the energy that radiates down toward the ocean’s surface survives-a portion is either absorbed or reflected by dust and clouds. Lou and Kim could calculate the amount of heat that could penetrate the dust and reach the surface of the North Atlantic after knowing the concentration of atmospheric dust as measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard a NASA satellite. “We’re not saying that El Nino does not have a substantial influence on sea surface temperatures, but rather that dusts is an important factor that we cannot ignore anymore. The 2007 hurricane season appears to be another one in which forecasts for an above-normal hurricane season have failed”, Lou says.
This entry was posted on Thursday, December 27th, 2007 at 5:50 pm and is filed under Mission History, Public Relations. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
