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| Sévellec, Florian; Drijfhout, S. S.. |
| The “signal‐to‐noise paradox” implies that climate models are better at predicting observations than themselves. Here, it is shown that this apparent paradox is expected when the relative level of predicted signal is weaker in models than in observations. In the presence of model error, the paradox only occurs in the range of small signal‐to‐noise ratio of the model, occurring for even smaller model signal‐to‐noise ratio with increasing model error. This paradox is always a signature of the prediction unreliability. Applying this concept to noninitialized simulations of Surface Atmospheric Temperature (SAT) of the CMIP5 database, under the assumption that prediction skill is associated with persistence, shows that global mean SAT is marginally less... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00514/62519/66825.pdf |
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| Sévellec, Florian; Naveira Garabato, A. C.; Huck, Thierry. |
| The impact of mesoscale eddy turbulence on long-term, climatic variability in the ocean's buoyancy structure is investigated using observations from a mooring deployed in the Drake Passage, Southern Ocean. By applying the Temporal-Residual-Mean framework and characterizing the variance contributors and the buoyancy variance budget, we identify the main source and sink of long-term buoyancy variance. Long-term buoyancy variance amplitude is set by long-term vertical velocity fluctuations acting on the steady stratification. This baro-clinic buoyancy flux is also the main source of the variance, indicative of the effect of large-scale baroclinic instability. This source is balanced by a sink of long-term buoyancy variance associated with the vertical... |
| Tipo: Text |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00658/77057/78356.pdf |
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| Moat, B. I.; Sinha, B.; Josey, S. A.; Robson, J.; Ortega, P.; Sévellec, Florian; Holliday, N. P.; Mccarthy, G. D.; New, A. L.; Hirschi, J. J.-m.. |
| An ocean mixed layer heat budget methodology is used to investigate the physical processes determining subpolar North Atlantic (SPNA) sea surface temperature (SST) and ocean heat content (OHC) variability on decadal-multidecadal timescales using the state-of-the-art climate model HadGEM3-GC2. New elements include development of an equation for evolution of anomalous SST for interannual and longer timescales in a form analogous to that for OHC, parameterization of the diffusive heat flux at the base of the mixed layer and analysis of a composite AMOC event. Contributions to OHC and SST variability from two sources are evaluated i) net ocean-atmosphere heat flux and ii) all other processes, including advection, diffusion and entrainment for SST. Anomalies in... |
| Tipo: Text |
Palavras-chave: Atmosphere-ocean interaction; Climate variability; Energy budget; Balance; Fluxes; Heat budgets; Fluxes; Surface temperature. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00502/61395/65060.pdf |
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| Sinha, Bablu; Sévellec, Florian; Robson, Jon; Nurser, George. |
| Global surface warming since 1850 consisted of a series of slowdowns (hiatus) followed by surges. Knowledge of a mechanism to explain how this occurs would aid development and testing of interannual to decadal climate forecasts. In this paper a global climate model is forced to adopt an ocean state corresponding to a hiatus (with negative Interdecadal Pacific Oscillation, IPO, and other surface features typical of a hiatus) by artificially increasing the background diffusivity for a decade before restoring it to its normal value and allowing the model to evolve freely. This causes the model to develop a decadal surge which overshoots equilibrium (resulting in a positive IPO state) leaving behind a modified, warmer climate for decades. Water mass... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00624/73629/73066.pdf |
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