Year: 2025
Type: article
Abstract: We consider the two-layer QG model with linear bottom friction and, possibly, background planetary 𝛽. We derive two-layer QG energy budgets in wavenumber space for eddy available potential energy (EAPE), baroclinic eddy kinetic energy (EKE), and barotropic EKE, a particular decomposition that has previously been overlooked. The conversion between EAPE and baroclinic EKE, 𝑇 W , has a strong dependence on both bottom drag strength and planetary 𝛽. At the deformation scale, 𝑇 W is always negative, representing the conversion of EAPE to EKE via baroclinic instability. For strong, linear bottom drag, 𝑇 W is positive at large scales due to frictional energization of the baroclinic mode, providing a large-scale EAPE source. With weak-to-moderate bottom drag and moderate-to-strong planetary 𝛽, 𝑇 W is the dominant source of EAPE at large scales, converting baroclinic EKE that has experienced a baroclinic inverse cascade back into EAPE, and thus closing a novel and exclusively baroclinic energy loop. With planetary 𝛽, zonal jets form and the dominant large-scale processes in the energy cycle of the system, e.g., barotropic dissipation and the peak of positive 𝑇 W , occur at the meridional wavenumber corresponding to the jet spacing, with no zonal wavenumber component. Importantly, the traditional source of large-scale EAPE, barotropic stirring of the baroclinic mode, is not a part of this 𝑘 x = 0 energy cycle, and thus plays a secondary role. The results suggest that consideration of two-dimensional processes is requisite in order to understand the energetics and physics of baroclinic geophysical jets.
Source: Journal of Fluid Mechanics
Author: Matthew Lobo
Institution: Princeton University
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Climate action
Open Access status: hybrid
Estimated APC paid: $3,550
Award: G292782501
OpenAlex ID: W4416067146