海陆分布对夏季东亚季风影响的数值试验

我们利用有限区域五层原始方程模式做了二组数值试验,一组是用五层模式和真实的海陆分布进行数值积分,模似真实的东亚夏季风环流,另一组是用五层模式和人为的海陆分布进行和第一组试验类似的数值积分,然后将两组数值试验的结果进行比较。 数值试验的结果表明:(1)东亚夏季风系统中位于印度和中南半岛的两个季风槽、西南季风的三个中心和低空越赤道气流[2][3]的形成与南亚地区东西向的海陆分布有密切的关系,如果没有印度半岛和中南半岛,两个季风槽将会消失,而三个西南季风中心也可能变为一个。(2)如果没有非洲大陆,索马里以东的越赤道气流的强度将明显减弱,相应的低空急流中心也会随之消失。(3)青藏高原的存在大大加强了地区间南北向的热力对比,因此它对南亚和我国南方近地面季风有很明显的加强作用。但高原的加强作用与它的地理位置有很大的关系,如果阿拉伯海和孟加拉湾不是海洋而是陆地,也就是说青藏高原离印度洋的平均距离要比现在大得多,那末它对季风的加强作用就会随之减弱。反之,如果印度和中南半岛不是陆地而是海洋,那末高原离印度洋的平均距离就会减小,它的加强作用也会得到相应的增大。 

NUMERICAL EXPERIMENTS OF EFFECTS OF LAND-SEA DISTRIBUTION ON EAST ASIA SUMMER MONSOON

Two sets of numerical experiments were performed using a 5-layer limited area primitive e-quations model. One simulated East Asia Summer monsoon circulation with real land-sea distributions and the other with artificial ones. Their results were compared.It is concluded that the generation of 2 monsoon troughs, 3 SW monsoon cores and low-level cross-equatorial flows is closely associated with the east-west land-sea alignment in South Asia, for the absence of the Indian and Indo-china Peninsulas would result in the disappearance of the troughs and the reduction of the cores from 3 to 1 ; the intensity of the cross-equatorial flows east of Somali would significantly drop and the corresponding low-level jet would go should there be no the African continent; the Tibetan Plateau increases near-surface monsoon in South Asia and southern China substantially due to its geographic location, in that the enhancement of monsoon would weaken if the Arabian Sea and the Bay of Bengal were masses of land instead of ocean and contrarily, it would be larger if the 2 peninsulas were ocean rather than land.