[A-CG33] Multi-scale ocean-atmosphere interaction in the tropics

[ACG33-P02] Generation mechanisms of the 2008 coastal El Niño event

*Tomoya Noguchi¹, Tomoki Tozuka¹ (1.The University of Tokyo)

Keywords:2008 Coastal El Niño

Coastal El Niño events are associated with anomalously warm sea surface temperatures along the coast of South America and can cause flood damage in the coastal areas. Thus, it is important to clarify their mechanisms, but the mechanisms have been mainly discussed qualitatively. Although most coastal El Niños occur simultaneously with basin-scale El Niño events, a coastal El Niño event occurred without El Niño in 2008. In this study, the generation mechanisms of the 2008 coastal El Niño event are investigated by conducting a closed mixed-layer heat budget analysis using a regional ocean model. The results indicate that the surface heat flux and vertical mixing terms were important for the development of this event. For the surface heat flux term, both an anomalously thin mixed layer that enhances heating by the climatological surface heat flux and reduced latent heat loss due to negative wind speed and atmospheric specific humidity anomalies played an important role. On the other hand, a decrease in both the vertical diffusion coefficient and the vertical temperature gradient were found to be important for the vertical mixing term.