Attractor dimension of time-averaged climate observables: insights from a low-order ocean-atmosphere model

Davide Faranda (1, 2, 3) , Gabriele Messori (4) , Stéphane Vannitsem (5)

1 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
2 London Mathematical Laboratory
3 ESTIMR - Extrèmes : Statistiques, Impacts et Régionalisation
4 Bolin Centre for Climate Research
5 IRM - Institut Royal Météorologique de Belgique [Bruxelles] - Royal Meteorological Institute of Belgium

The ocean and atmosphere have very different characteristic timescales and display a rich range of interactions. Here, we investigate the sensitivity of the dynamical properties of the coupled atmosphere-ocean system to time-averaging. We base our analysis on a conceptual model of the atmosphere-ocean dynamics which allows us to compute the attractor properties for different coupling coefficients and averaging timescales. When the averaging time is increased, the local dimension shows a non-monotonic behaviour for short averaging times, but ultimately decreases for windows longer than 1 year. The analysis of daily, monthly and annual instrumental and reconstructed indices of oceanic and atmospheric circulation supports our results. This has important implications for the analysis and interpretation of long climate timeseries with a low temporal resolution, but also on the possible convergence of climate observables for long time-averages toward attractors close to hyperbolicity.

Domaines: Planète et Univers [physics]; Océan, Atmosphère; Dynamique Chaotique [nlin.CD]

Davide Faranda, Gabriele Messori, Stéphane Vannitsem. Attractor dimension of time-averaged climate observables: insights from a low-order ocean-atmosphere model. Tellus A, 2019, ⟨10.1080/16000870.2018.1554413⟩. ⟨hal-01759822⟩