14 DAY TRIAL // Over the past few years, scientists studying how the Amazon rainforest changes through the seasons have been baffled by a phenomenon that defied explanation – the trees appeared to be getting greener between June and October, when the Amazonian Basin experiences its yearly dry season.
A new study conducted by experts at NASA finally managed to clear up this mystery. A paper detailing the findings is published in the latest issue of the top scientific journal Nature.
According to data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Terra and Aqua satellites, and measurements taken by the Geosciences Laser Altimeter System (GLAS) on the NASA Ice Cloud and land Elevation Satellite (ICESat), it would appear that the Sun-sensor geometry is responsible for the faulty readings.
“We think we have uncovered the mechanism for the appearance of seasonal greening of Amazon forests – shadowing within the canopy that changes the amount of near-infrared light observed by MODIS,” explains NASA Goddard Space Flight Center expert Doug Morton.
After the team controlled for the relative position of the Sun with regards to the orbital location of the MODIS sensors, it was determined that the Amazon rainforest in fact does not change very much during the dry season.