[A-CG30] Multi-scale ocean-atmosphere interaction in the tropics

[ACG30-09] The roles of diabatic heating for the seasonality of the Atlantic Niño

★Invited Papers

*Hyacinth C. Nnamchi¹, Mojib Latif¹, Noel S. Keenlyside^2,3, Joakim Kjellsson¹, Ingo Richter⁴ (1.GEOMAR Helmholtz Centre for Ocean Research Kiel, 2.Geophysical Institute, University of Bergen, and Bjerknes Centre for Climate Research, Bergen, Norway, 3.Nansen Environmental and Remote Sensing Center, Bergen, Norway, 4.Application Laboratory, Research Institute for Value-Added-Information Generation, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan)

Keywords:Bjerknes feedback, Atlantic Niño, Diabatic heating, ITCZ

The physics underlying the Atlantic Niño remain under debate; however, the role of diabatic heating which represents the atmospheric component of the Bjerknes feedback loop is often overlooked. In this study, we use multiple observations to show that diabatic heating variability that is linked to the seasonal migration of the inter-tropical convergence zone controls the seasonality of the Atlantic Niño. The strongest diabatic heating variability in spring leads that in the SST in summer, whereas the atmospheric response to the SST variability is relatively weak. This can be linked to net surface heat flux tendencies which drive the mixed-layer temperature anomalies in spring, but is the major damping term in June-July when the SST variability peak, although observational uncertainty is quite large. Entrainment is the dominant heating term associated with the peak SST variability in June. Our findings point to the existence of a strong meridional variability in the atmosphere, which by terminating the Bjerknes feedback, controls the seasonality of the Atlantic Niño.