黄河上游丰、枯水年汛期及前期的环流特征分析

运用有关台站的水文气象观测资料,分析了近80余年来黄河上游径流的丰枯变化特征,并对典型丰、枯水年对应的500 hPa高度距平场、OLR场、亚洲阻高和南风输送等环流特征进行了研究。结果表明,丰水年,从后冬开始到汛期,极涡始终保持偏强的态势;同样,在位势高度的垂直分布上也早形成了有利于降水的上高下低的形势;强对流中心有一个东移、北抬、加强、扩大的发展趋势。夏季,我国青藏高原及西北地区东部的对流活动较强,容易造成降水。乌拉尔山、贝加尔湖阻高的建立,加强了亚洲经向环流,丰水年中多数年份有乌拉尔山阻高,而枯水年中多数年份却没有。水汽输送的明显差异直接导致黄河上游来水的丰、枯。丰水年,我国中西部80°~110°E范围内整层为南风控制,而枯水年基本为北风控制。

Studies on Atmospheric Circulation Anomaly of Flood Period and Prefreshet Period in the Highest and the Lowest Flow Years in the Upper Reach of Yellow River

The both Change characteristics of high flow and low flow years since 1920 and their circumfluence characteristics of 500 hPa height fields,OLR fields,Asia blocking high,along with south wind transportation have been analyzed.The results show that in the high flow summer,the Polar vortex always keeps a stronger state from late winter to summer,there are south Asian highs called as east pattern in the upper levels and the Plateau vortex in the lower levels in the the upper reach of Yellow River;there are the strong convection centers move east and north-ward,and the centers trend to strengthened and expanded;the convection activity is stronger in the Qinghai-Tibet Plateau and the east of the northwest China;also there are the blocking highs southerly flow in entire levels over the the upper reach of Yellow River occurring over the Ural Mt.,but the opposite is true in the low-low years of summer.