Thermodynamic controls of the Atlantic Nio.
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Prevailing theories on the equatorial Atlantic Nio are based on the dynamical interaction between atmosphere and ocean. However, dynamical coupled ocean-atmosphere models poorly simulate and predict equatorial Atlantic climate variability. Here we use multi-model numerical experiments to show that thermodynamic feedbacks excited by stochastic atmospheric perturbations can generate Atlantic Nio s.d. of 0.280.07K, explaining 6823% of the observed interannual variability. Thus, in state-of-the-art coupled models, Atlantic Nio variability strongly depends on the thermodynamic component (R(2)=0.92). Coupled dynamics acts to improve the characteristic Nio-like spatial structure but not necessarily the variance. Perturbations of the equatorial Atlantic trade winds (1.53ms(-1)) can drive changes in surface latent heat flux (14.35Wm(-2)) and thus in surface temperature consistent with a first-order autoregressive process. By challenging the dynamical paradigm of equatorial Atlantic variability, our findings suggest that the current theories on its modelling and predictability must be revised.
author list (cited authors)
Nnamchi, H. C., Li, J., Kucharski, F., Kang, I., Keenlyside, N. S., Chang, P., & Farneti, R.
complete list of authors
Nnamchi, Hyacinth C||Li, Jianping||Kucharski, Fred||Kang, In-Sik||Keenlyside, Noel S||Chang, Ping||Farneti, Riccardo