Group seminar on 13. December, 14:15 CET

Decomposition of the horizontal divergence and its spectra into Rossby and non-Rossby components

Valentino Neduhal

In the extratropics, where we have a frequency gap between Rossby and inertia-gravity (IG) dynamical regimes, horizontal divergence is assumed to be a good proxy for IG waves. In the tropics, the frequency gap between the two dynamical regimes is filled with the Kelvin and mixed Rossby-gravity waves and as a result, the validity of this assumption comes into question. Here, a unified approach for the analytical computation of the horizontal divergence and associated divergence spectra, using the eigensolutions of the linearized primitive equations, will be presented. This method allows us to decompose the global horizontal divergence, as well as the associated divergence spectra, into the Rossby and non-Rossby wave contributions. The method is applied to the ERA5 data for August 2016. and resulting divergence is compared with observations over the tropical Atlantic from Bony and Stevens (2019). Decomposition of resulting divergence and divergence spectra to the Rossby, IG, Kelvin, and mixed Rossby-gravity waves contributions is performed and their contributions to the total divergence are discussed.