Desert Dust Feeds Amazon Forests   
       
   April 29, 2015: The Sahara Desert is one of the least hospitable climates on   
   Earth. Its barren plateaus, rocky peaks, and shifting sands envelop the   
   northern third of Africa, which sees very little rain, vegetation, and life.   
       
   Meanwhile, across the Atlantic Ocean thrives the world's largest rainforest.   
   The lush, vibrant Amazon basin, located in northeast South America, supports a   
   vast network of unparalleled ecological diversity.   
       
   So, what do these seemingly different climates have in common? They are   
   intimately connected by a 10,000 mile long intermittent atmospheric river of   
   dust.   
       
   https://www.youtube.com/watch?v=s7lVGhTPQAY&feature=youtu.be   
       
   A new ScienceCast video examines an unlikely link between two continents. Play   
   it   
       
   Every year, intense Saharan winds send enormous clouds of dust on a   
   trans-Atlantic journey to the Amazon basin. This dust, much of it originating   
   in an ancient lakebed in Chad, is rich in phosphorus. When it reaches the   
   rainforest, the remains of long-dead organisms of the Sahara provide crucial   
   nutrients to the rainforest's living flora. Phosphorus, which is essential to   
   plant growth, is in short supply in the Amazon. Desert dust dumped into the   
   forest every year helps to diminish this deficit.   
       
   NASA researchers are studying this dusty link between Amazon and Sahara, to   
   understand how it operates and how it might be affected by climate change.   
       
   "We know that dust is very important in many complex ways," says Hongbin Yu,   
   an atmospheric scientist at the University of Maryland who works at NASA's   
   Goddard Space Flight Center in Greenbelt, Maryland. "Dust affects climate and,   
   at the same time, climate change will affect dust."   
       
   "As researchers," he adds, "we ask ourselves two basic questions: "How much   
   dust is transported? And how does climate change affect the amount of dust   
   that travels across the Atlantic?"   
       
   Data from NASA's CALIPSO satellite, launched in 2006, may provide the answers.   
   For the first time, CALIPSO has quantified the amount of dust that makes the   
   trans-continental voyage-and the numbers are impressive: of the 182 million   
   tons (or nearly 700,000 semi trucks' worth) of dust that leave the Sahara each   
   year, 27.7 million tons, or 15% of the total are scattered over the Amazon   
   basin.   
       
   CALIPSO, short for "Cloud-Aerosol Lidar and Infrared Pathfinder Satellite   
   Observation," uses a laser range finder or lidar to scan Earth's atmosphere   
   for the vertical distribution of dust and other aerosols. It regularly tracks   
   the Sahara-Amazon dust plume.   
       
   One of the things CALIPSO has revealed is the connection's varia   
   ility-changing as much as 86 percent between 2007 and 2011. Why?  The answer   
   could lie in the Sahel, the long strip of semi-arid land on the southern   
   border of the Sahara. Yu and his colleagues have found a possible connection   
   between rainfall in the Sahel and the amount of dust transported over the   
   Atlantic. When rainfall in the Sahel is higher, the volume of dust is lower.   
       
   The exact reason behind this correlation is unknown, but Yu has some ideas.   
   It's possible that the increased rainfall could cause more vegetation to grow   
   in the Sahel, thus leaving less sand exposed to powerful winds. Another   
   possibility centers on the wind.  The amount of rainfall is correlated with   
   wind patterns that can sweep dust from the Sahara and the Sahel into the upper   
   atmosphere, which is basically a superhighway to the Amazon.   
       
   Thanks to CALIPSO's unprecedented 3D observations of atmospheric dust,   
   scientists can begin to create models to predict how the dust may impact   
   climate in the future-and how it nurtures the lush forests of South America   
   today.   
       
   For more news about unexpected connections, on Earth and other planets, stay   
   tuned to Science.nasa.gov   
       
   Credits:   
   Author: Rachel Molina | Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.99   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)