Eddy Detection from SSHA and SST Data Changming Dong Contributors: Francesco Nencioli, Yu Liu, Xiayan Lin

Outline SSHA Derived Geostrophic Velocity SST Derived Thermal Velocity Apply “Velocity Geometry-based Automated Eddy Detection Scheme” to the derived velocity fields

Example: Synthesis of SST, SSHA, and Drifters for an Eddy

Application: Kuroshio Extension

SSHA-derived Geostrophic Velocities

Eddies Detected from SSHA

SST-derived Thermal Velocity Where D is the vertical scale, α is the expansion coefficient β is salt contraction coefficient.

SST-derived Thermal Velocity A Sobel gradient operator is used to calculate SST gradients. where A is the SST matrix divided by grid size A pseudo-velocity vector V= (Ux,Uy), where Ux= - Gy; Uy= Gx on the northern hemisphere Ux= Gy; Uy= Gx on the southern hemisphere

Example: Thermal Velocity

Pseudo-EKE in the Northern Pacific Ocean

Comparable with EKE from SSHA

Compared with EKE from Global Surface Drifter Data

EKE Westward Propagation U= 6 cm/s at 24~25 N

Eddy Identification Using SST-derived Thermal Velocity Adapted from Dong et al (2010)

Examples of Eddies Identified by SST

Example: Eddy Tracking

Eddy Distribution in Kuroshio Extension

Eddy Statistical Analysis

Example: Track Eddies Using SST-derived Thermal Velocity