Southern Great Plains (SGP) Experiment 1999

The 1999 Southern Great Plains Experiment was conducted from July 8th through 19th, 1999 over the USDA Oklahoma mesonet hydrological site. The goal of the experiment was to image soil moisture variations using S- and C-band radiometric channels. Although L-band channels provide greater direct sensitivity to soil moisture, the implementation of higher-frequency channels such as at S- and C-band is more straightforward on either aircraft or satellite platforms.

In 2001, a C-band imaging radiometer (the Advanced Microwave Scanning Radiometer, or AMSR-E) was launched as part of the NASA EOS Aqua platform. AMSR-E is a conically-scanned imaging sensor supporting a dual-polarization channel at 6.92 GHz. The utility of this AMSR band for soil moisture retrieval depends on the degree to which both beam-filling and vegetation effects can be compensated. To study these effects, as well as those of anthropogenic interference at the AMSR 6.92-GHz band, a the PSR/C scanhead was flown on the NASA P-3 aircraft in grid patterns over central Oklahoma. The overflights included coverage almost daily coverage of the well-instrumented Little Washita hydrological site. The SGP99 data from the PSR over Oklahoma clearly show 50-70 K decreases in upwelling horizontally-polarized brightness temperature as the result of a major precipitation event that deposited 1-2" of rain, along with increases in brightness of similar magnitude during the subsequent dry-down phase. The images obtained from this experiment represent the first application of high-resolution C-band radiometric imaging of soil moisture, in particular using constant-incidence angle conical scanning.

V 7/08/99	V 7/09/99	V 7/11/99	V 7/14/99	V 7/15/99	V 7/19/99
H 7/08/99	H 7/09/99	H 7/11/99	H 7/14/99	H 7/15/99	H 7/19/99