四川盆地夏季水汽输送特征及其对旱涝的影响

Characteristics of Summer Water Vapor Transportation in Sichuan Basin and Its Relationship with Regional Drought and Flood

利用1981—2000年夏季观测资料,分析了四川盆地夏季平均的水汽输送状况及四川盆地典型旱涝年的水汽输送差异特征,并在此基础上,初步分析了四川盆地旱涝异常的大气环流背景。结果表明:四川盆地的夏季水汽主要来源于青藏高原、孟加拉湾及南海地区。当西太平洋副热带高压偏北偏西时,其外侧东南风可以把南海水汽带到盆地西部,孟加拉湾及青藏高原水汽受到阻挡被迫停留在盆地西部,形成了盆地西部异常的水汽辐合,东部异常的水汽辐散,由此导致四川盆地西涝东旱。反之,当西太平洋副热带高压偏南偏东时,其西南侧的南海水汽不能到达盆地西部,只能到达盆地东南部,而孟加拉湾及青藏高原水汽则可以进入盆地东部,在盆地东部形成异常的水汽辐合,在西部形成异常的水汽辐散,造成四川盆地西旱东涝。

Using the observational data in summer from 1981 to 2000,the water vapor transportation characteristics over Sichuan basin in summer are analyzed,especially in typical drought and flood years.The results indicate that the water vapor over Sichuan basin in summer mainly originates from Tibetan Plateau,Bay of Bengal and South China Sea.When the West Pacific Subtropical High（WPSH） shifts northward and westward,the southeast wind outside of it can bring the water vapor in South China Sea to the west of Sichuan Basin;the water vapor from Bay of Bengal and Tibetan Plateau are held up and only can stay in the west of Sichuan basin.So anomalous water vapor converges in the west of Sichuan,and diverges in the east.These lead to flood in the west of Sichuan and drought in the east.By contrast,when the WPSH shifts southward and eastward,the southwest water vapor outside of it cannot extend to the west of Sichuan basin,only can extend to the southeast,but the water vapor from Bay of Bengal and Tibetan Plateau can extend to the east.So it forms anomalous water vapor convergence in the east of Sichuan basin and divergence in the west,and brings to drought in the west and flood in the east.