Towards Better Understanding of Eddy Variation Using SST Data:

Application in the Northern Pacific Ocean

Changming “Charles” DongIGPP, University of California, Los Angeles

Yu LiuSCSI, Chinese Academy of Science, GuangZhou, China

Acknowledgements: NASA PO Grant, F. Nencioli, R. Lumpkin, M. Lankhorst, J. Vanzequez,

E. Armsrong, Y. Chao, J. McWillimas. D. Chen, and Y. Guan.

Outline

• Motivation• Pseudo-Velocity Derived from SST Data• Pseudo-EKE• Cohesive Eddies Product from REMSS SST• Summary

OBJECTIVE • Set up a global oceanic eddy data set by synthesizing available

observational data

• Observational data: SST, SSHA, global surface drifters, Argo data, and other in-situ data

• Eddy Detection Tools a. Nencioli and Dong et al (2009, JAOT) (Automated Vector Geometry Eddy Detection) b. Dong et al (2010, JAOT, submitted) (Automated Loops Detection from Surface Drifters) c. Dong et al (2010, IEEE-GRSL, submitted) (Automated Eddy Detection Scheme from SST Data)

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

Why we need a synthesis of these data: Abnormal Eddies

Application: Kuroshio Extension

SST-derived Pseudo-VelocityA 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 hemisphereUx= Gy; Uy= Gx on the southern hemisphere

Example: Pseudo-Velocity

More About Pseudo-Velocity

Where D is the vertical scale, α is the expansion coefficient β is salt contraction coefficient.

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 Pseudo-Velocity

Adapted from Dong et al (2010)

Example: Eddy Tracking

Application to REMSS SST (9km) in North Pacific Ocean

Statistical Analysis

REMSS SST(2006-2008)

AVISO SSHA(1993-2008)

Summary

• Motivated by an objective to develop a global oceanic eddy data set by synthesizing available observational data

• Pseudo-velocities derived from SST data are used for eddy Analysis

• So far, we have finished KE region and NP. We will move on to the global ocean

Example: Eddy Automatic Track Using SST-derived Pseudo-Velocity