Mechanisms controling the sea surface temperature and precipitation anomalies during contrasted years, 2010 and 2012, in the tropical Atlantic

• Main Author: Vasconcelos Nogueira Neto, Antonio
• Other Authors: Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Paul Sabatier - Toulouse III, Hervé Giordani, Philippe Peyrille
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2019
• Subjects: Oceanic mixed-layer budget; Atmospheric water budget; Tropical Atlantic; Regional modeling; Bilan de chaleur dans la couche de mélange océanique; Bilan d'eau atmosphérique; Atlantique tropical; Modélisation régionale; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; North Atlantic
• Online Access: https://theses.hal.science/tel-02498758; https://theses.hal.science/tel-02498758/document; https://theses.hal.science/tel-02498758/file/2019TOU30010B.pdf

The Atlantic Marine ITCZ (AMI) is a regional manifestation of the ITCZ over the warm water of the tropical Atlantic oceans. Few studies have been devoted to document the processes driving the evolution of the SST and precipitation, most of which were centered on the eastern side of the basin. The present study provides an analysis of the evolution of the ocean and the atmosphere over the Western part of the Atlantic for two contrasted years in Sea Surface Temperature (SST), 2010 and 2012, that were respectively the warmest and coldest years observed during the 1982-2015 period. The causes of interannual and seasonal anomalies of SST are first explored via an oceanic mixed-layer (ML) heat budget performed from Argo floats, satellite-based data and ERAI-Interim atmospheric reanalysis for the period 2007-2012. The surface latent heat flux was found to be under-estimated by 20 W/m2 and conducted to erroneous vertical mixing in the whole domain. Correction of these surface fluxes yielded to residuals which were assimilated to vertical turbulent mixing at the mixed-layer base, which fell into realistic range. Once corrected, the ML budget shows that the observed SST anomalies in 2010 and 2012 were generated by anomalous wind stress and, consequently, anomalous latent heat flux in the north Atlantic during winter. The wind-induced horizontal advection plays a fundamental role in balancing the surface flux in the south Atlantic in 2012. The north tropical Atlantic appears as a key region for the generation of the SSTs pattern observed in 2010 and 2012. The second part of the study analyses the building of the 2010 and 2012 rainfall anomalies and the underlying mechanisms. On seasonal average, 2010 shows a more intense rainfall over the basin while 2012 exhibits a meridional dipole of precipitation with a rainfall maximum shifted 5 degrees north of its climatological location. An analysis of the water budget integrated vertically indicates that the anomalous vertical advection of moisture is the leading term that ...