The time for 500 hPa height reaching maximum correlation to SST is 2 months later in latitude of 10°and 9 months in latitude of 30°than equatorial zone. And the response of atmospheric circulation over extratropic performs as wave train, and the response is more significant in the condition of warmer SST.
Period 1(7500—6600a BP) was a flourishing period of extratropical vegetation. The spore-pollen assemblage in this period was rich in extratropic vegetation, but indigent in tropical and semi-tropical vegetations. Compositae and Gramineae were very abundant, demonstrating a cold and humid palaeoclimate type in this period.