Preliminary Study of Oceanic Eddies Detected by Tiangong-2 Interferometric Imaging Radar Altimeter

Abstract

Oceanic eddy, which plays an important role in ocean thermal cycling, is a significant branch of oceanic scientific research. Mesoscale eddies can be observed by multiple sensors. However, sub-mesoscale or small scale eddies cannot be detected by conventional radar altimeters. The Interferometric Imaging Radar Altimeter (InIRA) on Tiangong-2 provides a large amount of images for the observation and investigation of sub-mesoscale or small scale eddies. 100 InIRA images obtained during 2016–2018 are used to investigate possible mechanisms of the appearance of eddies in InIRA images. Result shows that under a moderate wind speed of 3–5 m/s, film mechanism is the main form of oceanic eddies and under a considerable near-water wind speed of 5–12 m/s, and the wave/current interaction mechanism comes into action. The interferometric data of InIRA are processed to detect eddies after a series of procedures. It is shown that the phase change is corresponding to ocean surface height anomaly induced by eddy. Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) and chlorophyll-a (CHL) data are used to verify eddies identified from InIRA images. Result shows that the center of eddy with lowest SST corresponds to the highest CHL concentration.