Science Meetings

Aquarius Scatterometer Calibration and Bias Drift Correction
Fore, A., Tang, W., Hayashi, A., and Yueh, S. (13-Nov-14)

In this talk, we show that Aquarius scatterometer calibration has provided stable L-band backscatter observations over the entire mission duration of more than three years. We analyze the calibration using the ocean as a reference, and we track the calibration stability using a numerical weather product coupled with an ocean geophysical model function. We show an initial bias drift on the order of 0.1dB occurring on a timescale of approximately 1.5 months, after which the calibration has been extremely stable. We observe a very similar drift in all channels and beams indicating a transient drift in a portion of the underlying shared scatterometer hardware.

We also verify the absolute calibration using the Amazon rainforest as a calibration reference target, following the work of other L-band radars such as Phase Array type L-band Synthetic Aperture. We find that all three beams are calibrated to better than 0.1dB as compared to previously published results.

We propose for the end-of-prime-mission final Aquarius product a correction for this initial calibration drift. We empirically fit an exponential curve to the observed calibration drift, which removes this transient bias. We show this calibration drift removes biases in the retrieved wind speed and biases between the observed minus expected backscatter over the ocean.

The authors are with the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109. Copyright 2014 California Institute of Technology, Government sponsorship acknowledged.