Characterizing Earth´s surface using moderate resolution 14 GHz scatterometer imagery: early results from NSCAT construction

Small-scale vegetation maps are important for climatology. Because of the very large continental regions involved, AVHRR imagery and its derivative vegetation index products with resolutions between 1 and 12 km have been the preferred source material for many of these maps. Cloud cover is, however, a serious problem. Scatterometers are active microwave instruments used to measure ocean wind speed and direction. Seasat did pioneering oceanographic work. The launch of ERS-1 in 1991 provided further evidence of the scatterometer´s worth. The ERS-1 advanced microwave instrument (AMI), operating in wind scatterometer mode, is capable of land and sea imaging with pixel resolutions of approximately 50 km. Launched in August 1996, the NASA scatterometer (NSCAT) was also designed to measure ocean wind vectors. However, like its SASS predecessor, NSCAT data is also acquired over land. Though collected at a resolution of 25 km, resolution enhancements permit image reconstruction to image cell approaching 8 km. When reconstructed to this moderate resolution, the NSCAT data can be an important addition to AVHRR for global monitoring of cloudy regions. In other words, the scatterometer can be viewed as an active microwave instrument for land and ice imaging, as well as wind assessment. The purpose of this paper is to report preliminary results of research designed to measure the characteristics of the land surface as depicted in reconstructed NSCAT imagery