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Irina I. Rypina, Lawrence J. Pratt, Julie Pullen, Julia Levin, and Arnold L. Gordon

Abstract

Techniques from dynamical systems theory have been applied to study horizontal stirring of fluid in the Philippine Archipelago. The authors’ analysis is based on velocity fields produced by two high-resolution (3 and 6 km) numerical models. Particular attention is paid to identifying robust surface flow patterns and associating them with dominant Lagrangian coherent structures (LCSs). A recurrent wind-driven dipole in the lee of the coastline is considered in detail. The associated LCSs form a template for stirring, exchange, and biological transport in and around the dipole. Chaotic advection is argued to provide a relevant framework for interpreting mesoscale horizontal stirring processes in an archipelago as a whole. Implications for the formation of filaments, the production of tracer variance, and the scale at which stirring leads to mixing are discussed in connection with an observed temperature record.

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Tracy Haack, Dudley Chelton, Julie Pullen, James D. Doyle, and Michael Schlax

Abstract

High-resolution mesoscale model sea surface temperature (SST) analyses and surface wind stress forecasts off the U.S. West Coast are analyzed on monthly time scales for robust signatures of air–sea interaction as the surface winds encounter ocean surface features such as SST fronts, filaments, and eddies. This interaction is manifest by the linear relationship, or coupling coefficient, between the downwind SST gradient and wind stress divergence and between the crosswind SST gradient and wind stress curl evident from analysis of fields averaged over 29 days. This study examines fields from the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) model, spanning the summer months, June–September, for four consecutive years, 2002–05. Relative to several models evaluated previously, coupling coefficients are much closer to those calculated from Quick Scatterometer (QuikSCAT) satellite measurements. In addition, the summertime correlation between the wind stress derivative field and its corresponding SST gradient field on monthly time scales agrees well with satellite-derived correlations. Sensible and latent heat flux fields are also analyzed for features indicative of pronounced air–sea exchange associated with SST influence.

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