Fig. 9: Schematic diagrams describing mechanisms of the NAT SSTA phase changes from DJF to MAM.

a1, a2 are the processes of atmospheric forcing on SSTAs and oceanic Feedback on atmospheric circulation in the NAT SSTA phase persisting case. b1, b2 are same as (a1, a2), but for NAT SSTA phase transition case. The red (blue) shaded area denotes the warm (cold) SSTA; the solid red (dashed blue) circle indicates the positive (negative) geopotential height anomaly; The solid blue (red) arrow denotes the cold (warm) advection; the dashed purple arrow denotes increased/decreased atmospheric baroclinicity.