Amazonian Drought - Does the SeaWinds Scatterometer Active Microwave Data Contain a Signal?


A strong drought occurred in southwestern Amazonia in 2005. The sensitivity of neotropical evergreen broadleaf forests to drought is still not well-known. Interpretation of the optical/NIR signal of drought impact on forest function is compromised by variable atmospheric aerosol depths and frequent cloudiness. We analyzed about 10 years (Aug. 1999 - Nov. 2009) of active microwave backscatter collected by SeaWinds on QuikScat (Ku-band; frequency = 13.4 GHz, wavelength = 2.24 cm) over northern South America, using data from the NASA Scatterometer Climate Record Pathfinder project at Brigham Young University ( We processed both horizontally (HH) and vertically (VV) polarized backscatter on the ascending orbit (morning overpass) at a minimum spatial resolution of about 4.5 km, and a minimum temporal resolution of 4 days, and developed monthly ‘full-record’ backscatter climatologies. Monthly backscatter anomalies from these climatologies showed a large region of reduced backscatter in the western Amazon region developing over the 2005 dry season, with maximum extent and magnitude in Sept. 2005. We interpret this signal as a drier than normal vegetation canopy, and we compare spatial and temporal patterns in backscatter anomaly to precipitation anomaly data from the Tropical Rainfall Measurement Mission (TRMM), and to other ground- and satellite-based data sets.


Earth Sciences, Earth Systems Research Center

Publication Date


Journal Title

EOS, Transactions American Geophysical Union


American Geophysical Union Publications

Document Type

Conference Proceeding