The surface conditions of a small semi-enclosed ocean (the Japan Sea), largely controlled by the volume transport of the warm current, influence the monthly mean atmospheric circulation over the northwestern Pacific via active cyclogenesis. The new dynamical processes induced by the Japan Sea are proposed in this letter. When the surface temperature in the Japan Sea is lowered in a regional atmospheric model, the monthly mean potential vorticity is increased over the Japanese Islands, and the monthly mean Okhotsk Low is intensified at the 500-hPa level. In the case of an amplified Okhotsk Low, the mean cyclonic flow transports a cold air over the Japan Sea toward the Pacific and transports relatively warm air over the Bering Sea toward Siberia. Such westerly/easterly air mass advections over the northwestern Pacific area could produce the Japan-Siberia temperature anomaly in the lower-level troposphere via enhancement of the Okhotsk Low, which contributes to the weakness of the synoptic-scale north-south temperature gradient at 120°-180°E. This newly-found westerly cold/easterly warm ocean air-mass advection enhanced by the amplified quasi-stationary eddy that acts to reduce the temperature gradient is distinct from poleward heat transport by well-known transient baroclinic waves or annual mean Ferrel circulation.
All Science Journal Classification (ASJC) codes
- General Earth and Planetary Sciences