2.1 Data Sources
The Tropical Rainfall Measuring Mission (TRMM, available from NASA,
http://trmm.gsfc.nasa.gov/) 3B42 V7 daily data with 0.25-degree
spatial resolution were used for P . MODIS 16 monthly data (MODIS
16A2; Mu et al., 2007) were used for ET(http://www.ntsg.umt.edu/project/mod16) at 1 km resolution for the
global vegetated land areas and cover the period 2002 to 2013. The
latest ET product (Mu et al., 2011) implements the improvedET algorithm in Mu et al. (2007) and agrees well with
measurements from 46 eddy flux towers, including two towers in the
Amazon basin. The most recent release of the spherical harmonics GRACETWSA (RL05) was downloaded from the Jet Propulsion Laboratory
(available at http://grace.jpl.nasa.gov/). This distributed GRACE
product has been “destriped” and smoothed using a 300 km wide Gaussian
filter to minimize north-south stripes, and is appropriate for land
hydrology applications (Landerer & Swenson, 2012; Swenson & Wahr,
2006). The resolution of GRACE and TWSA data are 1-degree.
The sub-basin delineation map applied here was obtained from a
topography-independent analysis method (Mayorga et al., 2005) using the
vector river network from the Digital Chart of the World (DCW, Danko,
1992). The map includes the sub-basin boundaries of the major
tributaries to the main stem of the Amazon River
(http://daac.ornl.gov/LBA/guides/CD06_CAMREX.html).