Timothy Campbell

Ocean processes underlying surface clustering

Ageostrophic ocean processes such as frontogenesis, submesoscale mixed-layer instabilities, shelf break fronts, and topographic interactions on the continental shelf produce surface-divergent flows that affect buoyant material over time. This study examines the ocean processes leading to clustering, i.e., the increase of material density over time, on the ocean surface. The time series of divergence along a material trajectory, the Lagrangian divergence (LD), is the flow property driving clustering. To understand the impacts of various ocean processes on LD, numerical ocean model simulations at different resolutions are analyzed. Although the relevant processes differ, patterns in clustering evolution from the deep ocean and the continental shelf bear similarities. Smaller-scale ocean features are associated with stronger surface divergence, and the surface material clustering is initially dominated by these features. Over time, the effect of these small-scale features becomes bounded, as material traverses small-scale regions of both positive and negative divergence. Lower-frequency flow phenomena, however, continue the clustering. As a result, clustering evolves from initial small-scale to larger-scale patterns.

The Earth System Prediction Suite: Toward a Coordinated U.S. Modeling Capability

The Earth System Prediction Suite (ESPS) is a collection of flagship U.S. weather and climate models and model components that are being instrumented to conform to interoperability conventions, documented to follow metadata standards, and made available either under open source terms or to credentialed users. The ESPS represents a culmination of efforts to create a common Earth system model architecture, and the advent of increasingly coordinated model development activities in the U.S. ESPS component interfaces are based on the Earth System Modeling Framework (ESMF), community-developed software for building and coupling models, and the National Unified Operational Prediction Capability (NUOPC) Layer, a set of ESMF-based component templates and interoperability conventions. This shared infrastructure simplifies the process of model coupling by guaranteeing that components conform to a set of technical and semantic behaviors. The ESPS encourages distributed, multi-agency development of coupled modeling systems, controlled experimentation and testing, and exploration of novel model configurations, such as those motivated by research involving managed and interactive ensembles. ESPS codes include the Navy Global Environmental Model (NavGEM), HYbrid Coordinate Ocean Model (HYCOM), and Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS®); the NOAA Environmental Modeling System (NEMS) and the Modular Ocean Model (MOM); the Community Earth System Model (CESM); and the NASA ModelE climate model and GEOS-5 atmospheric general circulation model.

The Navy's coupled atmosphere-ocean-wave prediction system

An air-ocean-wave modeling system has been developed by the Naval Research Laboratory to provide improved predictive capabilities to the warfighter in regions that include an oceanic component. Each of the three operational models, run in a standalone mode, have provided 48 to 96 hour forecast guidance for the past several years. Utilizing the Earth System Modeling Framework, a model coupler exchanges needed information between the model components and interpolates between the model grids. This paper will discuss the model coupling and provide a brief overview of validation studies that have been performed in the Adriatic Sea, Ligurian Sea and Kuroshio extension, with a particular emphasis on air-sea interactions. Model studies presented here focus on the upper ocean (mixed layer) heat fluxes, near surface winds, temperature, moisture, the air-sea interaction, and the marine boundary layer characteristics. Validation studies presented here show the most improvements in ocean heat fluxes, due to a more realistic sea surface temperature. The coupled system is scheduled for operational implementation at Navy production centers beginning in 2011.

Wave-current interaction in the Florida Current in a coupled atmosphere-ocean-wave model

The interaction of waves and currents are investigated in the Florida Current region in two events in early April 2005 using a state-of-the-art coupled atmosphere-ocean forecast model that includes assimilation of observations. During the first event, strong northerly winds force swell southward opposing the Florida Current. Current-wave interaction results in larger significant wave heights than found without currents. The second event has south-easterly winds with a significant component along the current direction. In that case, significant wave heights are smaller for the simulation that includes wave-current interaction than without that feed-back. Wave heights at buoy locations near the coast is generally in good agreement with the models results, which implies that inclusion of wave-current interaction may not be important near the shore. The simulation includes events where the maximum winds reach 20 m/s and significant wave heights exceed 2 m.