Use of Airborne Infrared Remote Sensing to Characterize Submesoscale Eddies

Airborne remote sensing surveys off Santa Catalina Island, CA (33◦30′N 118◦31′W) were conducted as part of a larger study of the occurrence and behavior of submesoscale phenomena. This builds upon previous work by DiGiacomo and Holt (2001), who utilized SAR imagery to characterize the size and distribution of predominately cyclonic ’spiral eddies’ in the Southern California Bight. In the present work the thermal surface expression of the eddies is examined with high temporal and spatial resolution over several days in April 2011 and February 2013. All but one very small eddy (< 250 m diameter) were observed to be cyclonic, with a vorticity many times the Coriolis frequency. And while the location of the observed eddies was consistent with numerical model calculations made by Dong and McWilliams (2007), the observed size and time scales are smaller than model predictions. Methods to estimate eddy circulation and vorticity directly from the thermal imagery will be discussed and compared with in situ measurements. Inferences about localized mixing and flow instabilities can also be drawn from the imagery, and these too will be discussed in the context of in situ data. In addition to the eddies the imagery also reveals an incredibly rich background of fine-scale signatures. While we can quantify some aspects of this background we can at this point only speculate as to the underlying physical phenomena.