[A-CG35] Multi-scale ocean-atmosphere interaction in the tropics

[ACG35-10] Exploring the symmetries of pan-tropical connections between the tropical Atlantic and Pacific basins

*Rajashree Naha^1,2,3, Shayne McGregor^1,2,3, Martin Singh^1,2,3 (1.Monash University, 2.SCHOOL OF EARTH, ATMOSPHERE AND ENVIRONMENT (SEAE), 3.ARC Centre of Excellence for Climate Extremes (CLEx))

Keywords:Pan-tropical connections, Remote forcings, Tropical variability, Decadal variability

Recent analysis of pan-tropical interactions suggest that post-1980, the tropical Atlantic Ocean’s (TAO) influence on the tropical Pacific Ocean (TPO) appears to have become much more pronounced, while the tropical Indian Ocean’s (TIO) influence appears to have weakened. The present study explores whether and how decadal changes in TAO and TPO SSTs modulate these pan-tropical connections in an attempt to explain the recent dominance of the TAO. To this end, we carry out a series of idealised AMIP style experiments using ACCESS AGCM where the magnitude and sign of the decadal TAO SST signal is varied – presenting various warm and cool Atlantic scenarios. To understand further if these pantropical connections are influenced by changes in TPO SST, we carry out the above TAO experiments with both, warm and cool phases of Pacific decadal variability (PDV). We find that an imposed TAO warming largely leads to increases in TPO atmospheric temperature and stability, which leads to a decrease in average TPO precipitation where the most prominent changes are seen in June-August. These changes in TPO precipitation induced by TAO warming are largely mirrored when TAO cooling is added, while the TPO rainfall response remains relatively unchanged for phase changes of PDV. The TAO modulated TPO surface wind response, on the other hand, displays significant PDV phase asymmetries in the western equatorial Pacific, where the PDV+ changes being significantly stronger than PDV- especially. This suggests that the phase of PDV may be important in modulating pan-tropical connections.