The TRR 181 seminar is held by Jan Niklas Dettmer (Universität Hamburg) on December 15, Bundesstr. 53 20146 Hamburg, room 22/23.

Spectral Resolution of the Oceans Lorenz Energy Cycle

Abstract

Eddy kinetic energy (EKE) and the conversion terms of the Lorenz energy cycle are estimated from an eddy-resolving ocean model and resolved spectrally per horizontal wavenumber. The baroclinic conversion term (BC) exhibits a dipolar structure, where it is a source for EKE at scales close to the first baroclinic Rossby radius and a sink for EKE at larger scales close to the Rhines scale. The geographical and vertical distributions of the BC term are explored. It is found that in the ocean interior negative BC is limited to regions poleward of approximately 30° north and south. It is suggested that the cause is the transfer of eddy energy to Rossby waves and zonal jets equatorward of 30°. It removes eddy energy before it cascades up to the scale where negative BC takes place. Equatorward of 30° the existence of a closed energy loop is suggested. Positive BC produces EKE which cascades upscale where it is converted to available eddy potential energy (EAPE) by negative BC, which cascades downscale again. The sink of EKE partly balances the EKE produced by baroclinic instability. The energy loop traps a certain amount of energy. Finally the baroclinic conversion term is explored further in idealized model setups.