Simultaneous measurements of ku- and ka-band sea surface cross sections by an airborne Radar

The dual-frequency Airborne Precipitation Radar-2 (APR-2) was deployed during the Wakasa Bay Experiment in 2003, for validation of the Advanced Microwave Scanning Radiometer-EOS. Besides providing extensive observations of diverse precipitating systems, this Ku-(13.4 GHz) and Ka-band (35.6 GHz) cross-track scanning radar measured sea surface backscatter simultaneously. While the characteristics of the normalized sea surface cross section sigma⁰ at Ku-band are well understood and widely published, the existing experimental data concerning sigma⁰ at Ka-band are scarce and results are inconsistent. In this letter, the Ku/Ka-band sigma⁰ measurements collected by APR-2, together with the estimated uncertainties, are discussed. In general, the measured sigma⁰ at Ka-band at around 10deg incidence angle appears to be close to that at Ku-band sigma⁰, and Ka-band exhibits a nonnegligible difference in wind dependence with respect to Ku-band for moderate to high winds