IMPACT OF HORIZONTAL RESOLUTION ON OCEAN SURFACE ENERGY CASCADES COMPUTED IN FREQUENCY ANDWAVENUMBER DOMAINS

摘要

We compute spectral fluxes Π(K) and Π(ω) in wavenumber (K) and frequency (ω) domains, from QG turbulence simulations, realistic global models, and AVISO gridded altimeter data, Filtered model output is used to mimic the spatial and temporal filtering inherent in the construction of AVISO. Eddy viscosity, meant to roughly mimic energy transfer to smaller scales, yields a forward energy cascade to high wavenumbers in models, in apparent agreement with the AVISO Π(K). However, filtered model output also displays a forward cascade. The model fluxes Π(ω) demonstrate a tendency for nonlinearity to drive energy towards lower frequencies. This is seen in some regions of AVISO, while other regions display energy cascades towards higher frequencies. Once again, filtering exercises with the models demonstrate that the cascade to high frequencies seen in some regions of AVISO may be due to data smoothing. In summary, data smoothing makes it difficult to interpret spectral fluxes.