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 (http://www.scp.byu.edu/). 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
EOS, Transactions American Geophysical Union
American Geophysical Union Publications
Frolking, S., Milliman, T., Fahnestock, M., Palace, M. and Lammers, R. (2010), Amazonian Drought - Does the SeaWinds Scatterometer Active Microwave Data Contain a Signal?, Eos Trans. AGU, 91(26), Meet. Am. Suppl., Abstract B21A-06.