African Dust Fertilizing the Amazon Rainforest: An Assessment with Seven-year Record of CALIOP Measurements

Thursday, 18 December 2014
Hongbin Yu1,2, Mian Chin2, Tianle Yuan3, Huisheng Bian4, Joseph M Prospero5, Ali H Omar6, Lorraine Ann Remer7, David M Winker8, Yuekui Yang9, Yan Zhang2,10 and Zhibo Zhang11, (1)University of Maryland College Park, College Park, MD, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)Joint Center for Earth Systems Technology, Baltimore, MD, United States, (4)NASA Goddard Space Flight Ctr, Greenbelt, MD, United States, (5)University of Miami, Miami, FL, United States, (6)NASA/Langley Research Ctr, Hampton, VA, United States, (7)University of MD Baltimore County, Baltimore, MD, United States, (8)NASA Langley Research Center, Hampton, VA, United States, (9)NASA, Greenbelt, MD, United States, (10)GESTAR/MSU, Greenbelt, MD, United States, (11)University of Maryland Baltimore County, Baltimore, MD, United States
The productivity of Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of transported African dust in boreal winter and spring is considered an important nutrient input for the Amazon Basin, though its magnitude is not well qunatified. This study provides a remote sensing observation-based estimate of dust deposition in the Amazon Basin using a 7-year (2007-2013) record of three dimensional (3D) distributions of aerosol in both cloud-free and above-cloud conditions from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). It is estimated that the 7-year average of dust deposition into the Amazon Basin amounts to 15.1 ~ 32.1 Tg a-1 (Tg = 1012 g). This imported dust could provide 0.012 ~ 0.025 Tg P a-1 or equivalent to 12 ~ 26 g P ha-1 a-1 to fertilize the Amazon rainforest, which largely compensates the hydrological loss of P. The CLAIOP-based estimate agrees better with estimates from in-situ measurements and model simulations than what has been reported in literature. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3D nature of CALIOP aerosol measurements. The trans-Atlantic transport and deposition of dust shows strong interannual variations that are found to correlate with the North Atlantic Oscillation index in the winter season and anticorrelate with the prior-year Sahel Precipitation Index on an annual basis. Uncertainties associated with the estimate will also be discussed.