摘要:邻接青藏高原地区的中国西北地区是最大的欧亚干旱区，其降水变化对全球变化的响应和对干旱环境及其青藏高原气候变化都具有特殊的指示意义。基于1961～2018年中国西北地区144个站的逐日降水、逐月气温观测资料，分析了西北地区的降水变化特征及趋势。结果表明：（1）近60年以来，西北地区92%站点的年降水量呈现增加的趋势，只有甘肃东南部不到10%的站点呈下降趋势；（2）季节尺度上，春、夏、秋季中超过75%站点的降水呈现增加的趋势，但最显著的是，几乎所有站点在冬季的降水为增加趋势，秋、冬季降水的增加相对较少，反映了冬季风对西北地区降水影响的特点；（3）进入21世纪以来，西北地区夏季和年降水量仍然维持准3 a周期特征，春、秋季的周期具有阶段性、冬季降水量具有较稳定的约3 a周期，因此，自然周期变化对降水增加的贡献并不大。西北地区降水量在过去60年来确实呈现出增加趋势，尤其21世纪以来降水量持续增加，但增加的量是有限的，不足以改变其干旱半干旱的气候特征。
关键词:西北地区/
降水量/
时空特征/
周期分析
Abstract:The Northwest China, which is adjacent to the Qinghai-Tibet Plateau, is the largest Eurasian arid region. Its precipitation responses to the global climate changes, to the arid environment, and to the climate change in the Qinghai-Tibet Plateau region are special significance. Based on the observational data of the daily precipitations and monthly temperatures at 144 stations in Northwest China from 1961 to 2018, the characteristics and trends of the precipitation change in Northwest China are analyzed. The results showed that: (1) During nearly the last 60 years, 92% of the stations in Northwest China observed an increasing trend of annual precipitations, while less than 10% of the stations in southeastern Gansu observed a decreasing trend. (2) On the seasonal scale, precipitations at more than 75% stations showed an increasing trend in spring, summer, and autumn, however the most significant is that almost all the stations had an increasing trend of precipitations in winter. The increase of precipitations in autumn and winter was relatively small, which reflected the influence of winter wind on the precipitation in Northwest China. (3) Another feature is that since the beginning of the 21st century, the summer and annual precipitations in Northwest China have maintained a quasi-3 a cycle. The spring and autumn cycles have several stages, while the winter precipitation has a relatively stable cycle of nearly 3 a. Therefore, natural cycle changes do not contribute much to the increase of the precipitation. The precipitation in Northwest China has indeed increased over the past 60 years, especially since the beginning of 21st century when the precipitation has been continuously increasing. However, the increased precipitation amount is limited, which is not enough to change the arid and semi-arid climate characteristics in the region.
Key words:Northwest China/
Precipitation/
Spatial and temporal characteristics/
Periodic analysis
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