Positive feedback of winter ocean-atmosphere interaction in Northwest Pacific

摘要

Using monthly mean atmospheric re-analysis data and oceanic assimilation data product, the winter ocean-atmosphere interaction in middle and high latitude in Northwest Pacific was studied. Key regions were chosen to study the variations of Aleutian Low, the 500hPa westerly, the meriodional sea surface temperature (SST) gradient with three indices defined as Aleutian Low index, zonal index and meridional SST gradient between Kuroshio-influenced region and Oyashio-influenced region. The results show that when there is a deeper Aleutian Low accompanied by a stronger northerly wind in the western part of the Aleutian Low, the subpolar gyre of North Pacific is strengthened, the SST in the Oyashio-influenced region is decreased and the meridional SST gradient between Kuroshio-influ- enced region and Oyashio-influenced region is increased, which, in turn, will enhance the westerly jet in the upper troposphere due to thermal-wind relation. The strengthened westerly jet makes a favorable condition for the deeper Aleutian Low over North Pacific beneath the left part of the jet exit region. Consequently, a positive feedback forms there.