Spaceborne GNSS-R Observations of Mesoscale Ocean Eddies; Preliminary Results from Cygnss Mission

Mesoscale ocean eddies are swirling oceanic features with diameters of the order of hundreds of kilometers contributing to different vital processes such as transferring energy across the ocean. This study demonstrates the feasibility of detecting signature of the eddies in space-borne Global Navigation Satellite Systems-Reflectometry (GNSS-R) measurements for the first time. The GNSS signal reflections off the ocean surface collected by the CYGNSS (Cyclone GNSS) mission, are collocated with wind speed estimates from ERA-Interim reanalysis and MetOp ASCAT A/B scatterometer over the mesoscale eddies documented in Aviso's mesoscale eddy trajectory atlas. The analysis of the bistatic radar cross section (σ
⁰
) and wind speed retrievals between March 2017 and January 2018, reports several recognizable patterns over the eddies. As an example, the impact of eddy-induced SST (Sea Surface Temperature) anomalies on the overlying wind field, are discussed using two instances of warm- and cold-core eddies near the south coast of Japan. As the most striking fact, the technique shows noticeable promise in detecting ocean eddies as a new application of space-borne GNSS Reflectometry.