PV Anomalies In the Island Wake

Changming Charles Dong, James McWilliams, Alexander Shchepetkin

IGPP, UCLA

Leif Thomas

Wood Hole Oceanographic Institution

Outline

1. Review of the Island Wake Study

2. Shallow-Water Island Wake

3. PV balance

4. Summary

Review of Island wakes

1) Marine Environmental Implication

2) Oceanic response to wind curl and sheltering

3) Oceanic Flow Past an Island(s)

Marine Environmental Implication

(Benitez-Nelson et al, Nature,2007)

(Basterretxea et al, 2002, DSR)

Divergence Convergence

Oceanic Response to Wind Curl (I)

(Dong and McWilliams, 2007 CSR)

(Surface Vorticity)

(Wind Stress and Curl)

LA

LA

Oceanic Response to Wind Curl (II)

(Caldeira and Marchesiello,2002,GRL)

Oceanic Response to Wind Sheltering

(Xie et al, 2001, Science)

(Barton, et al, 2000, JGR)

I. Deep-water Island Wake(the vorticity is generated within the lateral boundary when the bottom stress is negligible, (e.g, Boyer and Davis 2000, Dong et al, 2007)

II. Shallow-water Island Wake(inhomogenity in bottom stress and diabatic processes)

For the homogenous ocean, e.g. Signell,1989.For the stratified ocean, e.g, Heywood, 1996.

Oceanic flow past an island(s)):Oceanic flow past an island(s)):

YX

(Ertel PV)

YX

PV Anomalies

Surface PV Anomalies

PV anomalies

Full Ertel PVFull Ertel PV

(Adapted from L. Thomas’s Note)

(Personal communication with L. Thomas)

Tendency = ADV + FRIC + DIA + PRES + MOTION

Tendency

Where

The integral is calculated over a control volume bounded onIts sides by the isopycnals [ρ1 ρ2 ] x [x1 x2] x [y1 y2].

(Chapman and Lentz, 2005, JPO)

Tendency = ADV + FRIC + DIA + PRES + MOTION

Tendency = ADV + FRIC + DIA + PRES + MOTION

Tendency = ADV + FRIC + DIA + PRES + MOTION

Diabatic Processes decrease PV

Frictional Processes increase PV

Advection Processes redistribute PV

Summary:

In the shallow-water island wake, the PV anomaliesare asymmetrical in the northern and southern regionsof the island. Frictional and diabatic processes are dominantin the generation of the PV anomalies.

A general PV balance MATLAB package is availableto the community.