黄土高原秋季降水年际和年代际气候变化特征

Climate change characters of precipitation in autumn among decades and years on Loess Plateau

根据黄土高原地区分布较为均匀的39个气象观测站（1961～2000年）及西峰国家基准气候站（1938-2003年）秋季降水序列资料，应用NCEP刷CAR（1968-2003年）500hPa高度距平场再分析资料，利用区域性各年代距平场和西峰各年代逐年累积秋季降水距平百分率分析得出：黄土高原20世纪60（90）年代秋季降水全区域偏多（偏少），70（80）年代除北部偏多外中南部转为略少（均略少）；秋季降水持续阶段性转折变化特征突出，存在5个转折变化年份和6个相对持续阶段，继20世纪90年代持续偏少阶段之后，从2001年开始转入一个相对偏多阶段，有利于冬小麦生产；秋季降水的大气环流背景为：偏少（多）年份，极地冷空气影响势力弱（强），新疆高压脊强（弱），特别是偏多年份新疆低压槽活跃。

Based on the autumn precipitation sequence data of 39 meteorological observation stations （1961 -2000） with symmetrical distribution on Loess Plateau and Xifeng state benchmark climate station （1938- 2003）, and by applying the sub-analysis data of NCEP/NCAR（1968-2003） 500 hPa altitude anomaly fields, this paper studied the characters of accumulated precipitation anomaly among different years and decades. The result showed that the autumn precipitation of the whole region was partial to more in 1960s and less in 1990s on Loess Plateau; and the precipitation was partial to more in the north part and partial to less in the middle and south part in 1970s-1980s. There was a marked change character of autumn precipitation on Loess Plateau, that is, five years of transition change and six yeas of relative continuance phase. After the continuous less precipitation phase of 1990s, it has entered a relatively more precipitation phase, being propitious to the production of winter wheat. The atmosphere circumfluence background of precipitation in autumn was that in less precipita- tion yeas, the force of cold air from the polar region was feeble and the Xinjiang high-pressure ridge was strong; but in more precipitation years, the force of cold air from the polar region was strong and the Xinjiang low-pressure trough was active.