C-Band Satellite Scatterometer Intercalibration

A methodology of intercalibration of C-band space-borne scatterometers is developed and applied to European Remote Sensing satellite-1 (ERS-1), European Remote Sensing satellite-2 (ERS-2), and Meteorological Operational satellite (METOP) scatterometer data. Assuming that the differences between the instruments can be represented by an incidence-angle-dependent bias, this paper presents and discusses four methods, providing an estimate of that bias and of its standard deviation. Model-based methods performed more accurately than a direct comparison of sigma(0). The latter provides a systematic larger positive bias. The methodology is applied to ERS-1 and ERS-2 data acquired during the tandem mission in 1996. The same methodology is applied to ERS-2 and Advanced Scatterometer (ASCAT) data acquired in December 2008. Generally, the bias between the ERS-1 and ERS-2 scatterometers is smaller than 0.2 dB over most incidence angles, and the four methods provide relatively consistent results. The bias between ERS-2 and ASCAT is slightly higher, reaching 0.4 dB at certain incidence angles. These results suggest that these scatterometers need to be intercalibrated to achieve a consistent backscatter data.