1998年青藏高原东侧边界层风场与长江暴雨洪水的关系

应用1998年6～8月四川省和重庆市探空资料,分析了青藏高原东侧大气边界层风场演变与长江上游暴雨和长江洪水的关系.结果表明:1998年夏季长江上游的暴雨天气与高原东侧成都边界层风场变化密切相关,当成都边界层为东北风时,高原东侧边界层维持气旋式偏东流场,长江上游未来产生暴雨等强对流天气;当为西南风等其他风向时,高原东侧边界层维持反气旋式偏南流场,未来是无降水天气;高原东侧边界层的动力激发作用是1998年长江上游暴雨产生的重要机制.并且,再次证明了西邻青藏高原的成都是长江上游天气变化关键点的观点.

The PBL Wind Field at the Eastern Edge of the Tibetan Plateau and Its Relations with Heavy Rain-Flood of the Changjiang River in 1998

By using the radiosonde data in Sichuan Province and Chongqing Municipality during the June-August of 1998, the relationship between wind field in planetary boundary layer (PBL) at the eastern edge of the Tibetan Plateau and heavy rain-flood of the Changjiang River are analyzed. The result shows that the heavy rain weather at the upper reaches of the Changjiang River is closely connected with the variation of PBL wind field in Chengdu at the eastern edge of the Tibetan Plateau in 1998. When it is northeast wind in the PBL in Chengdu, the PBL at the eastern edge of the Tibetan Plateau maintains easterly cyclonic flow field, and these will be strong convection weather such as heavy rain at the upper reaches of the Changjiang River. When non-northeast wind such as southwest wind maintains, these will be southerly anticyclonic flow field, and rainless weather. The PBL dynamical trigger at the eastern edge of the Tibetan Plateau is a important mechanism for heavy rain at the upper reaches of the Changjiang River in 1998. Furthermore, it is confirmed again that the Chengdu station near the Tibetan Plateau is the key point for the weather variation at the upper reaches of the Changjiang River.