Sensitivity of Midlatitude Atmospheric Circulation Decadal Alteration to Observed Pacific-Indian SSTs during 1960–1999

Observations reveal that the Pacific-Indian Ocean surface temperatures underwent a pronounced decadal alteration around the late 1970s, accompanying a significant transition of midlatitude atmospheric circulation. Here, we investigate the relative importance of different domains of the Pacific-Indian Ocean SSTs with a more detailed division to atmospheric decadal anomalous patterns during 1960-1999 by conducting SSTs experiments with an atmospheric general circulation model. Our results suggest that in this decadal transition, the SST anomalies in the Pacific Ocean (PO) may play a significant role to North Pacific climate, but a negative effect to observed North Atlantic alteration, while warming trend of tropical Indian Ocean (TIO) may play a crucial role to the strengthening trend of the North Atlantic Oscillation (NAO), but induce a negative phase of the Pacific North Atlantic (PNA) against observation. Further analysis indicates that the North Pacific Ocean (NPO) contributes to a PNA- phase opposite to tropical central and eastern Pacific (TCEP) and tropical western Pacific (TWP), with weaker range and strength both in middle and upper troposphere. Moreover, the PO effect illustrates an inconvenient truth that the process of SSTs affecting atmospheric circulation may not be considered as a linear superposition of the TCEP, TWP and NPO oceans.