Satellite and model estimates of Saharan dust reaching the Amazon differ threefold

Estimates of how much African dust settles on the Amazon basin each year range from about 8 to 28 million tonnes, depending on method. A 2015 study led by NASA's Hongbin Yu used CALIPSO satellite lidar data from 2007 to 2013 and put the figure near 28 million tonnes, with an uncertainty range of 8 to 48 million.

A 2020 study led by Joseph Prospero of the University of Miami checked NASA's MERRA-2 model against filter measurements from Cayenne, French Guiana, and arrived at 8 to 10 million tonnes. A 2023 study by Xurong Wang and colleagues, using Cayenne and Brazilian measurements, found about 10 million tonnes for 2013 to 2017.

A 2021 study suggested the satellite approach may overstate dust because fine particles block more light per tonne than assumed. In Prospero's model, 89% of deposition near Cayenne fell between February and May.

Why it matters: The spread shows how satellite retrievals of aerosols need ground measurements to be reliable. Sahara and Sahel dust sources, including Mauritania, Mali and Chad, feed the budget, so African dust monitoring has bearing on nutrient and carbon models.