NOVEL— assessing meridional vis-à-vis zonal mechanisms of the Atlantic Niño

• Applicant: Dr. Hyacinth Nnamchi, Ph.D.
• Subject Area: Atmospheric Science ; Oceanography
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 456490637

The Atlantic Niño, also referred to as Atlantic zonal mode or equatorial mode (EM hereafter), is the leading mode of interannual sea-surface temperature (SST) variability in the equatorial Atlantic. EM is associated with profound climatic impacts over the adjacent African and South American continents and drives near-global atmospheric teleconnections, which, for example, exert influences on European climate and Indian summer monsoon. Further, knowledge of EM’s state could enhance the prediction of major El Niño events in the tropical Pacific and its far-reaching impacts. In a recent study, I have put forward a new paradigm in which the EM is governed by interactions between the ocean and atmosphere zonal and meridional circulations. The overall goal of NOVEL is to exploit this novel framework to enhance understanding of EM’s dynamics and predictability. The specific objectives are: (1) to identify from observations, reanalysis products and climate models the processes that govern the coupling between the oceanic and atmospheric circulations, zonal and meridional, including EM’s low-frequency modulations and sensitivity to remote forcing; (2) to evaluate the representation of zonal and meridional circulation variability, atmospheric and oceanic, in models participating the Coupled Model Intercomparison Project phase 6 (CMIP6), including the role of biases and improvements relative to its predecessor CMIP5; (3) to further prediction systems through investigation of EM-forecast ensembles performed with different versions of the Kiel Climate Model (KCM), the newly developed Flexible Ocean and Climate Infrastructure (FOCI), TRIATLAS models (NorCPM, EC-Earth and MeteoFrance) and operational systems. Metrics to characterize oceanic and atmospheric circulation variability across coupled models will be derived through seasonal maximum covariance analysis. Partially coupled and pacemaker experiments will help to assessing EM’s sensitivity to remote forcing. Finally, predictions will be performed with a number of climate models (with improved representation of the equatorial Atlantic by making use of the results from EU PREFACE), and analyzed alongside the operational systems. NOVEL will offer new insights into EM’s dynamics and predictability, and guide targeted model improvement.

• DFG Programme: Research Grants