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NASA scientists have performed the first multi-year study

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using satellite data to measure the 3-D distribution of dust

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that travels from the Sahara Desert to the Amazon rainforest.

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The Sahara is the world’s largest desert.

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At more than 3 million square miles,

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it’s almost the size of the continental United States.

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Each year, Saharan dust is lifted from the ground,

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and transported by winds on a 3000-mile journey

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across the Atlantic Ocean.

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A portion of the dust collects in the Amazon basin

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—the largest rainforest on the planet.

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Although dust particles are small,

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no larger than around a tenth of the width of a human hair,

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they form massive plumes that can be seen from space.

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NASA’s CALIPSO satellite was launched in 2006

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to study the vertical structure of clouds and particles

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in Earth’s atmosphere.

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CALIPSO observations from 2007 through 2013

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show that on average,

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182 million tons of dust leaves Africa each year.

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Of this amount, about 27 million tons

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is deposited in the Amazon basin.

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Sahara dust contains phosphorus,

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which is an important nutrient for plants.

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In the tropic region, the phosphorus is quite limited.

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So it’s important to estimate how much dust

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from the desert is transported to the Amazon.

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The study shows Saharan dust adds phosphorous to the soils

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that help compensate for losses

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due to surface runoff and floods.

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However, the amount of dust transported to the Amazon

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changes from year to year.

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According to the study, this variation is closely associated

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with changes in rainfall in the Sahel,

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a belt of semi-arid land just south of the Sahara.

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When the Sahel was dry, the dust transport to the Amazon

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in the next year would increase.

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When it was wet,

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dust transport would decrease.

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Using satellites to get a clear picture of dust is important

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for understanding, and eventually using computers to model

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where that dust will go,

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now and in future climate scenarios.

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