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On the Surface Current Measurement Capabilities of Spaceborne Doppler...

Wineteer, A., H. Torres, and E. Rodriguez (2020), On the Surface Current Measurement Capabilities of Spaceborne Doppler Scatterometry, Geophys. Res. Lett., 47, e2020GL090116, doi:10.1029/2020GL090116.

Wide-swath spaceborne Doppler scatterometry is a promising technique for the simultaneous measurement of global ocean surface winds and currents. The technique has been proven from airborne platforms, and here we use the lessons learned to examine a range of implications for a spaceborne system. We use a Doppler scatterometer simulator and a state-of-the-art global circulation model to generate surface current measurements and their random errors. We find that a feasible instrument could measure 5 km gridded surface currents with typical random errors between 10 and 25 cm/s. For higher wind speeds, the random error in surface current decreases logarithmically. This level of accuracy allows for the computation of surface current relative vorticity and horizontal divergence with typical wavelength resolutions of 15–30 and 25–60 km, respectively. Unlike previous studies, we find that these measurements do not require multiday averaging, opening up new avenues for monitoring global ocean circulation. Plain Language Summary Our understanding of the ocean, the atmosphere, and the Earth system as a whole has been profoundly bettered by the global perspective of space-based sensors. For decades, radar scatterometers have measured global ocean winds from space, contributing significantly to our scientific understanding of the atmosphere and improving forecast models. With a similar instrument, and the addition of “Doppler” capability, a Doppler scatterometer can measure ocean winds and ocean surface currents simultaneously, which opens new avenues to understanding the ocean, the atmosphere, and how they interact. This type of instrument has been successfully built and proven to work on airborne platforms but has yet to be implemented on a satellite. In this work, we have simulated the measurements of a spaceborne Doppler scatterometer to understand the oceanic scales that such an instrument might be able to observe. We find that ocean currents and their derivatives could be measured at scales better than 30 km. This enables the study of many currently unobserved ocean processes, including the vertical circulation of the ocean and the transport of plastics, kinetic energy, heat, and gasses.

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Physical Oceanography Program (POP)