A link between dust and hurricanes?

At right, Hurricane Floyd in the late summer of 1999 before it made its northward turn up the eastern seaboard of the United States. Image from NCDC.

Hurricanes capture the human imagination. Hurricanes are the perfect natural disaster for the 21st century. Unlike their brethren disasters, hurricanes are somewhat predictable, their massive symmetric swirl can be seen on satellite images days before the hurricanes reach the short of a tropical island or the coastline of a massive continent. Best yet, hurricanes are beamed into your livingroom via satellite. Whether you are watching a panting weatherman on CNN yelling barely coherent words about how this is the worst hurricane to hit since the last one, or you are watching on the Weather Channel as some slightly idiotic meteorologists stations themselves 15 feet from the ocean as 95 mile per hour winds batter their highly makeuped faces, hurricanes are something that everyone can understand, successfully visualize and ultimately relate to.

At right, dust blows off the Sahara Desert over Western Africa on it’s way across the Atlantic. The presence of dust can be seen as a gentle haze over much of the left 1/3 of the picture. The image was taken by MODIS satellite June 6, 2008.



So, maybe it’s more surprising that it ought to be that hurricanes can be impacted by the presence of tiny earthen particles in the atmosphere, known as mineral dust. Mineral dust is picked up by the wind from dirt, dust and sand on the Earth’s surface and blown hundreds or thousands of miles, sailing across oceans on rivers of air high above, often landing on differing continents. When the wind direction and speed are just right and the soil conditions just so, lots of dust can be picked up at once, and the sky darkened as dust obscures the sun’s rays. These impressive massive floating storms of dust are known as dust storms, and recent findings suggest that these dust storms makes hurricanes less likely to form or thrive in their presence.

Recently, this topic was discussed on all things considered on NPR. Follow this link and click on the red button with a speaker icon to take a listen to the report.

Dust seems to oppose hurricane formation in two ways, first by absorbing sunlight it cools the ocean beneath it. Hurricanes rely on warm waters to gather the energy and moisture necessary for them to develop into intense storms. Secondly, dust tends to be found in a dry, hot airmass lofted between 1 and 5 kilometers above the surface. This dry, hot layer tends to choke the hurricane by stealing moisture from the storm, and interfering with the convection that provides the heat engine for the hurricane.



Interestingly enough, dust storms are maximized each year during the summer, coincident with hurricane season. This coincidental timing increases possibility that there are meaningful dust – hurricane interactions each season. The figure to the right if from research we have done here at Stony Brook, showing the average amount of absorbing aerosols, including dust, that are found in the atmosphere each season. As you can see there are a lot of these aerosols over Africa, and as you head westward it slowly decreases. This suggests that dust plumes pick up large quantities of dust, which gets transported long distances, increasing the likelihood that it has a chance to interact with tropical systems.

Dust is what I study, and this finding is quite exciting. I am working hard to find ways to anticipate the quantity of dust storms that will occur each year based on meteorological conditions. If said forecasts help to further predict how many hurricanes each year, I will have made a lasting contribution to humanity, which is always the goal of a research scientist.