Important Role of the Somalian Cross-Equator Flow in the Onset of the South China Sea Summer Monsoon
索马里跨赤道气流对南海夏季风爆发的重要作用

Through analyses of NCEP/ NCAR reanalysis data, the important relationship between the onset of the summer monsoon in the South China Sea and the cross-equator southerly wind in the Somalia region is clearly shown. Corresponding to the outbreak of the South China Sea summer mon- soon, there are always an enhancement of the westerly wind over the equatorial Indian Ocean and an onset of cross-equator southerly wind in the Somalia region. If the outbreak of the South China Sea summer monsoon is earlier(later), the enhancement of westerly wind over the equatorial Indian Ocean and the onset of cross-equator southerly wind in the Somalia region are all earlier(later). It can be sug- gested that the steady onset of Somalian cross-equator southerly flow is one of important physical mechanisms to cause the outbreak of the South China Sea summer monsoon. The steady Somalian southerly wind will lead to an increase and eastward expanding of the westerly wind over the equatorial Indian Ocean, and then the southwesterly wind will occur over the South China Sea.