高原季风强弱对南亚高压活动的影响

分析了高原季风强弱对夏季南亚高压活动和三峡库区旱涝的影响,揭示了如高原夏季风偏强(弱),育藏高原上空及其以东地区100hPa南亚高压也偏强(弱),位置偏北偏东(偏南偏西)。高原季风强年,南亚高压脊线6月北跳比多年平均早1候,8月南撤晚1～2侯;高原季风弱年。脊线北跳晚1～2候,南撤早1候。同时显示了高原夏季风强年,5～6月三峡库区降水随着南亚高压脊线北移而增多,7～8月三峡库区降水减少;高原夏季风弱年,主汛期前期库区降水少,后期降水略有增多。

Impact of Strong/Weak Plateau Summer Monsoon on South Asia High Activity

Influence of the strong/weak summer monsoon over Qinghai|Xizang on the activity of 100 hPa South Asia high and drough/flood Three Gorge Reservior District were analyzed. It is found that there are good relationships between the intensity of 100 hPa South Asia high over Qinghai|Xizang Plateau and to its eastern area and the intensity of Plateau monsoon, its center is far northward and eastward(southward and westward) when the Plateau summer monsoon year is the strong(weak) year. In strong Plateau monsoon year, ridge axis of South Asia high jump to the north in June which is earlier 1 pentad than normal year, and withdraw to south in August which is later 1 or 2 pentads and nearly vice versa. Meanwhile, it is obtained that precipitition in Three Gorge Reservior District is increased from May to June, and one is decreased from July to August with ridge axis of South Asia high moving to the north when intensity of Plateau summer monsoon is strong. Otherwise, preceding precipitation in Three Gorge Reservior District is decreased, and following precipitation is more increased when intensity of summer monsoon over Qinghai|Xizang Plateau is weak. In addition, there are opposite correlation between the winter Plateau monsoon index and summer South Asia high and precipitation in Three Gorge Reservior District.