A Numerical Study of the Effect of Anomalous Surface Heating in the Kuroshio Current Region in Winter on the East Asian Subtropical Westerly Jet

The East Asian Subtropical Westerly Jet (EAWJ) is a narrow and strong westerly wind belt with large horizontal and vertical wind shears over the East Asian subtropical region, which is generally located at the north edge of the Western Pacific subtropical high. It plays a key role in linking weather systems over the mid-latitudes and low latitudes. Its northward jump is the signal of general circulation seasonal transition and the criteria for dividing the natural season of East Asia. Therefore, it is a meaningful work to further study the influencing features for its variations. Based on that climate model GAMIL successfully simulates the pattern and seasonal evolution of East Asian general circulation, the impact of anomalous surface heating in the Kuroshio Current region to the south of Japan and the Tibetan Plateau on the EAWJ is investigated by designing sensitive experiments with the GAMIL. The results indicate that strong heating in the Kuroshio Current region to the south of Japan in winter can cause the eastward shift of the East Asian trough, intensifying of the cold high pressure in the continent, Aleutian low pressure and western Pacific subtropical high, as a result, leads to strong winter monsoon circulation. Corresponding to variations of the geopotential height field, cyclonic difference circulation over the northeastern Pacific Ocean and anticyclonic difference circulation over the mid-high latitudes adjacent to the ocean are observed. The anomaly of geopotential height over the low latitudes south of the EAWJ is positive and the opposite situation occurs to the north of the EAWJ. Therefore, the meridional difference of air temperature is accordingly enlarged and the EAWJ is intensified.