ASCAT MetOp-A Backscatter Observations over the Global Land Surface: Application to Monitoring Recent Trends in Lake and Wetland Extent and to Monitoring Crop Growth over the United States
Abstract
This study evaluates the use of high-repeat C-band vv-polarized backscatter data from the Advanced Scatterometer (ASCAT) aboard the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) MetOp-A satellite for global-scale lake and wetland monitoring and for drought influences on crop growth. We apply an incidence angle normalization method to the ASCAT dataset and compare the normalized data with concurrent constant incidence angle, vv-polarized backscatter observation from the Ku-band SeaWind-on-QuikSCAT scatterometer (QSCAT) during mission overlap between November 2008 and 2009. We then combine the Ku-band backscatter time series of Seawinds-on-QuikSCAT (QSCAT; 1999-2009) with that of ASCAT (2008-present) and apply them in combination with co-located passive microwave data from the Special Sensor Microwave Imager (SSM/I) to quantify recent trends in global lake area and inundated wetlands extent between 1999 and the present. Initial results of our trend analysis show statistically significant (p < 0.1) wetting and drying with large rates of change in regions with increasing human activity and associated impacts on freshwater resources. Smaller rates of change are observable across large natural wetland complexes of the tropics and higher latitudes and may indicate recent trends in climate variability.We analyzed 4-years of ASCAT incidence angle normalized C-band backscatter and NEXRAD precipitation data over the contiguous United States. Large negative anomalies in backscatter are evident over the US during the 2011 and 2012 growing seasons. The backscatter anomalies were correlated with reduced growing season precipitation and with a reduction of annual crop yields reflecting drought-related impacts on above-ground net primary production. During periods of acute drought, differences in diurnal backscatter were reduced and in some cases reversed reflecting diminished nocturnal leave recovery. The results indicate that the C-band, vv-polarized ASCAT backscatter data provides a potentially important geophysical tool capable of identifying drought related vegetation response independent of and complementary to satellite optical/near-infrared remote sensing data. This work was supported by the NASA Terrestrial Ecology Program and the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Program. Portions of this work were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B51E0339S
- Keywords:
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- 0497 BIOGEOSCIENCES Wetlands;
- 1820 HYDROLOGY Floodplain dynamics;
- 0480 BIOGEOSCIENCES Remote sensing;
- 0402 BIOGEOSCIENCES Agricultural systems