基于SPI的石羊河流域气候干湿变化及干旱事件的时空格局特征研究

利用石羊河流域4个气象站1960—2013年逐月降水量资料,应用标准化降水指数(SPI)、游程理论等方法,分析石羊河流域近54年的气候干湿变化及不同时间尺度干旱事件时空演变特征。结果表明:1不同时间尺度SPI对降水量变化的敏感程度存在较大差异,时间尺度越小,SPI对一次降水的反应越明显。2石羊河流域年代际、年际和季的SPI在波动中均呈增加趋势,其中,冬季湿润化速度最快,对年湿润化过程的贡献最显著。31960—2013年,石羊河流域不同时间尺度干旱事件持续时间、干旱程度和干旱强度均呈减少趋势,且波动渐趋平缓;石羊河流域农业干旱和水文干旱最严重的时期分别为1964—1965年和1962—1964年。4两种时间尺度干旱事件持续时间的减少速度从上游至下游均逐渐变慢,上游乌鞘岭地区是农业干旱持续时间最长区域,永昌和下游民勤地区是水文干旱持续时间较长区域;两种时间尺度干旱事件干旱程度减少速度最快区域均在上游乌鞘岭地区;武威和民勤地区3月尺度干旱强度稍有上升,其它地区不同时间尺度干旱事件干旱强度均呈下降趋势,永昌地区是多尺度干旱事件干旱强度较大区域。

Temporal and spatial patterns of climate drought-wet and drought event based on Standard Precipitation Index in Shiyang River Basin

Shiyang River Basin is located in the northwest China, and it is a typical fragile ecosystem area. This region is extremely sensitive to climatic changes, and therefore, monitoring these changes can provide an important evidence for revealing trends indrought-wet transition mechanisms in drought-prone and arid regions of Northwestern China, this study aimed to investigate monthly precipitation data obtained from four stations in Shiyang River Basin. In particular, the Standard Precipitation Index (SPI) and Theory of Runs were adopted to analyze changes in climate drought-wet and space-time evolution of drought events on different time scale during a period of 54 years i.e., from 1960 to 2013. The main results of this study suggest that SPI characteristics at different time scale lead to SPI values were substantial sensitive to precipitation changes, and a smaller time scale resulted in a more sensitive response to one precipitation event. The inter-decadal, inter-annual and seasonal SPI showed an increasing trend. The wetting rate was the fastest in winter, which makes the largest contribution to annual wetting. The drought event duration, drought severity and drought intensity on different time scales showed a decreasing trend, and the fluctuations noticedwere gradually mild. The most serious agricultural drought and hydrological drought occurred during 1964 to 1965 and 1962 to1964, respectively. The drought event duration during two time scales reduced gradually from upstream to downstream, and the longest agricultural drought occurred in Wushaoling areas, whereas the longest hydrological drought occurred in Yongchang and Minqin region. Drought severity of the drought events during the two time scales reduced the fastest in Wushaoling areas. Except for the three-month scale for drought intensity showing a slight increase in Wuwei and Minqin regions, the intensity of drought events showed a decreasing trend in other regions on different time scales. More frequent drought events and relatively higher drought intensity were noted in the middle reaches of the river, especially in Yongchang region.