干旱是西北地区乃至全国主要的自然灾害之一。论文应用标准化降水指数(SPI)对西北地区近50 a来不同时段的特旱和重旱发生频次及其空间分布进行了计算分析,结果表明:标准化降水指数(SPI)作为一种干旱重建指标,适用于西北地区,也可以作为气候变化的监测指标;降水量的西增东减趋势与干旱频次的西部和东北减少、东南增加相对应,亦即气候变化在某种程度上缓解了新疆北部和青海西部的干旱,但加重了甘肃东南部和陕西中南部的干旱;与气候变化相对应,全西北地区干旱频次有总体下降的趋势,尽管干旱发生的地域持续在改变。
Drought is one of the main natural disasters in Northwest China, even in the whole country. In this article, the standardized precipitation index (SPI) was applied to reconstruct the drought at the different time scales in recent 50 years in Northwest China. Then the frequency and the spatial distribution were calculated and analyzed for the severely dryness and extremely dryness. The results show that SPI used as a drought reconstruction index, is suitable in Northwest China, and may also be taken as the monitor index of the climate change. The trend of increase of the precipitation in western part and decrease in eastern part is corresponding to the trend of drought frequency, which is upward in southeastern part and downward in northwestern part of Northwest China. That is to say, the climatic change alleviated drought in northern Xinjiang and western Qinghai, but aggravated drought in southeastern part of Gansu and southern and central Shaanxi. Corresponding with the climatic change, the drought frequency of the entire Northwest China has an overall trend of downward, although the drought region continues to change.
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