Enhanced Ocean Predictability Through Optimal Observing Strategies

Abstract

LONG-TERM GOALSThe primary long-term goal of our research is to develop optimal deployment strategies for drifter releases using templates derived from dynamical systems theory and to apply these to operational scenarios. The second goal is to improve current understanding of basic mesoscale and submesoscale oceanic processes. Both goals contribute to improved predictive capability of the marine environment. This research effort was initiated as a component of the DRI, Predictability of the Ocean and Atmosphere, and has contributed to the goals of that program by developing effective observation strategies for improved now-casts and forecasts of oceanic conditions. OBJECTIVESThree objectives were identified as important to achieving our long-term goals. First, integrate Lagrangian methods developed from dynamical systems theory into oceanographic applications. Second, use these methods to design optimal observing strategies with special emphasis on drifter deployments that achieve the maximum geographic coverage with the fewest units. Finally, apply the methodology to operational situations, specifically applications to data assimilating ocean models. APPROACHThe technical approach taken in this project builds on results obtained by the PI from prior ONR support as well as collaboration with investigators at other institutions. The approach has three basic components. The first is to objectively reconstruct Eulerian velocities either from data assimilating models or from synoptic current maps in a format that can be used for the Lagrangian analysis. Here we have adapted methods initiated by Rao and Schwab (1981) and used by Eremeev et al. (1992a,b) and Lipphardt et al. (2000) as well as others for rendering these velocity fields. The second part is to calculate the critical material curves from the velocity archives by Lagrangian analysis. Our approach is adapted from that used by Miller et al. (1997) and Poje and Haller (1999). Since then a number of new developments have occurred that may improve this approach in future applications.