Os processos de conversão de energia nos oceanos: uma revisão do Diagrama de Lorenz

Abstract

ABSTRACT. The energetic analysis is an important diagnostic tool for the identification of dynamic processes associated with events of energy conversion in the ocean. In brief, that analysis shows the energetic interactions which are taking place among the mean and eddy fields of a certain geophysical flow, as well as the transfers involved between the reservoirs of energy in the oceans. Those processes are detailed in the Lorenz Diagram which links, through four boxes, the reservoirs of the mean kinetic energy, eddy kinetic energy, mean potential energy and eddy potential energy of the flow. Moreover, the Diagram identifies the interactions that occur between those four energy forms, as well as the exchanges through the boundaries (sources and sinks). After an extensive review, we have identified that the specialized literature lacks in texts which detail the several mechanisms of energetic conversion among the main forms of energy in the oceans, with most publications detailing only part of those components. This article presents a detailed review on this subject, gathering information of several sources and having as main objective the step by step construction of the Lorenz Diagram, with their respective formulations. The discussion of each term of the Diagram is presented objectively thus enabling a better understanding of this tool, which is instrumental in summarizing the energy processes at a given area of the ocean.Keywords: Lorenz Diagram, potential energy, eddy kinetic energy, barotropic conversion, baroclinic conversion and quasi-geostrophy. RESUMO.A análise energéticaé uma importante ferramenta diagnóstica para a identificação de processos dinâmicos associados a eventos de conversão de energia no oceano. Esta análise, de uma forma sucinta, procura mostrar as interações energéticas que ocorrem entre os campos médio e turbulento de um determinado escoamento geofísico, bem como as transferências entre os reservatórios de energia nos oceanos. Estes processos são sumarizados pelo Diagrama de Lorenz que representa, através de quatro caixas, os reservatórios das energias cinética média, cinética turbulenta, potencial média e potencial turbulenta do escoamento do fluido geofísico, identificando as interações que ocorrem entre estas quatro formas de energia, bem como as trocas com o meio externo (fontes e sumidouros). Notadamente a literatura especializadaé escassa em textos que detalhem os diversos mecanismos de conversão energética entre as principais formas de energia nos oceanos, havendo algumas publicações que, dependendo da abordagem, detalham apenas alguns deles. Este trabalho apresenta uma revisão sobre o assunto, reunindo informações de diversas fontes e tendo como objetivo principal a construção, passo a passo, do Diagrama de Lorenz, com suas respectivas formulações. A discussão de cada termo do Diagramá e apresentada objetivamente, o que possibilitará um melhor entendimento desta ferramenta, a qualé de real importância para a sumarização de uma estimativa energética para uma dada região do oceano....

Brazil Current surface circulation and energetics observed from drifting buoys

“…BT represents the rate of generation of EKE by the interaction of the Reynolds stresses with the mean shear components, which can be interpreted in terms of the direction of eddy momentum flux relative to the mean momentum gradient [e.g., Dewar and Bane , 1989; Wilkin and Morrow , 1994]. Positive values of BT indicate that the eddy fluxes are down gradient and therefore energy transfer from the mean flow to the eddy field [e.g., Bryden , 1982; Rossby , 1987; Hall , 1991; Cronin and Watts , 1996; Azevedo et al , 2008]. Thus, in summary BT > 0 implies MKE → EKE.…”

Metal fate and effects in estuaries: A review and conceptual model for better understanding of toxicity

“…2). Estuaries are typically funnel-shaped, so the horizontal scales can increase several orders of magnitude moving seaward with respect to the upstream river, causing a reduction in the Rossby number (quotient between velocity and the product of the horizontal scale of movement and Earth's rotational velocity) (Azevedo et al, 2008). As a consequence, a higher influence of Earth's rotation in the circulation of low velocity and large horizontal scale flows is observed at high latitudes.…”

Energetics of eddy‐mean flow interactions in the Brazil current between 20°S and 36°S

“…The energy equations are presented here, but readers interested in a detailed description of the derivations of the kinetic and available potential energy equations are advised to consult the studies of Bryden [], Cronin and Watts [], Azevedo et al . [], Von Storch et al . [], Chen et al .…”