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Analysis of Coherent Microwave Data Collected on the Ocean over Two Decades
WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB
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The long-term goal of this project is to fully utilize microwave backscattering data sets that have been collected on the ocean over the last two decades. The prime objective is to better understand the formation of breaking waves on the ocean and their effect on microwave backscatter. The scientific objectives of this study are to investigate wave shadowing and wave modulation in low-grazing-angle backscatter from the ocean. Our approach is to reanalyze data sets taken with Doppler radars over the last two decades in an attempt to extract additional information on microwave backscatter from the ocean. These data sets have been taken from a variety of platforms ranging from airplanes and towers to blimps and ships using a variety of coherent microwave radars. In the work that we carried out in the past year, we looked for evidence of shadowing of microwave backscatter by ocean waves and applied boundbreaking wave theory to observed phase differences between modulated received power and scatterer velocities. It is common to think of low-grazing-angle backscatter from the ocean in terms of geometric shadowing. This work shows that on the open ocean this is a very bad model. Our work indicates that on the open ocean no evidence exists to indicate that any reduction at all in the incident fields takes place in geometrically shadowed regions at either VV or HH polarization. Therefore, models of low-grazing-angle backscatter will have to focus on more realistic causes in regions of very low backscatter, such as very low scatterer intensities. They cannot simply be brushed aside as shadowed regions.
APPROVED FOR PUBLIC RELEASE