冬季黑潮暖流区加热异常对东亚副热带西风急流影响的数值研究

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

通过对大气环流格点模式GAMIL性能的检验表明,模式较好地再现了东亚地区大气环流型态、高空西风急流变化及表面加热场的季节变化。在此基础上,设计敏感性试验研究了冬季西太平洋黑潮暖流关键区加热异常对高空西风急流影响,数值试验结果表明冬季西太平洋黑潮暖流区加热正异常将引起东亚大槽偏东,大陆冷高压、阿留申低压及位于低纬太平洋上的西太平洋副高均有所增强,从而导致了冬季风环流加强。相应地,东北太平洋上出现了明显的气旋差值环流,而在中高纬大陆海洋交界地区出现反气旋式差值环流;同时,西风急流区南侧的低纬地区位势高度及温度场为正异常,而北侧的中高纬地区为负异常,这种分布将使得急流区经向气压梯度和南北温差加大,导致急流的增强。模式结果分别从热力适应理论及热成风的角度验证了黑潮暖流区表面加热异常对急流的影响机理。

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.