水保所知识产出(1956---)知识库

基于标准化降水指数（SPI）方法，对1971—2017年大理河流域干旱变化特征及其与极端降水的联系进行了分析。结果表明：（1）不同时间尺度SPI对降水量变化的敏感程度不同，SPI1和SPI3适用于短期气象旱涝特征的识别，而SPI6和SPI12对揭示区域长期旱涝影响及持续时间效果较好。2种时间尺度SPI （SPI3和SPI12）的时间变异性均呈显著增加趋势。（2）不同季节SPI的变化趋势和干旱等级频次存在差异，仅冬季有一定的下降趋势，其余季节呈增加趋势，秋季最显著。年SPI波动幅度较大，总体上呈增加趋势，2001年以来最明显。干旱等级均以轻旱和中旱为主（21.2%~36.1%），夏、秋季发生干旱的频率最高。（3）干旱事件持续时间呈不显著的减少趋势，长时间尺度干旱事件平均持续时间、最长持续时间以及下降速度均大于短时间尺度。（4）降水集中程度增大会导致SPI1减小，增加干旱发生的可能性。典型极端降水可能会降低干旱发生的概率。

 The Dali River Basin is located in northwest China and is a typical fragile ecosystem area. This region
is extremely sensitive to climatic changes, and monitoring these changes can therefore provide an important basis
for decreasing the losses bought about by drought disasters. On the basis of the standard precipitation index (SPI),
the variation in drought characteristics and their relationship with extreme precipitation events in the Dali River
Basin from 1971 to 2017 were analyzed. The main results of this study suggest that (1) the annual precipitation initially
showed an increasing trend (from 1971 to the early 1990s) and fluctuated before the mid-1990s before it decreased and
then increased. The precipitation in the months from January to March, August, and December showed a downward
trend, whereas the precipitation in the other months showed an upward trend, which was particularly notable for
the month of September. SPI1 and SPI3 were suitable for identifying short-term meteorological drought and flood
characteristics, whereas SPI6 and SPI2 were suitable for revealing the long-term impact and duration of regional
droughts and floods. Temporal variations in the SPI (particularly SPI3 and SPI12) increased significantly. (2)
However, the trend of the SPI and the frequency of drought grade differed through the seasons. In winter, there
was a definite downward trend, whereas in the other seasons the trend was an increasing one, particularly in
autumn. The interannual SPI fluctuated greatly, showing an increasing trend overall, particularly since 2001.
Light drought and moderate drought were the predominant drought grades (21.2%-36.1%), and the frequency of
drought in summer and autumn was the highest. (3) The average duration, longest duration, and descending speed
of drought events at a long time scale were higher than those at a short time scale. In addition, the frequency of
days with daily precipitation ≥0.1 mm was not significantly changed over the study duration, which indicates that
the possibility of drought had not increased significantly in the Dali River Basin over the 47-year-range studied.
(4) The increase in the precipitation concentration (Rmax/Rtotal) will lead to a decrease in SPI1 and will increase
the possibility of drought. By contrast, an extreme precipitation will reduce the probability of drought. With the
increase in the maximum daily precipitation (>50 mm), the annual SPI increased and reduced the possibility of
drought.