三峡库区气象干旱演变特征及致灾因子危险性评价

Evolution Characteristics of Meteorological Drought and Assessment of Risk of Disaster Factors in the Three Gorges Reservoir Area

近年来三峡库区干旱灾害发生的强度和频率呈现加剧趋势,因此识别干旱的时空特征及致灾因子危险性,对于区域干旱预警和防旱减灾具有重要意义。利用三峡库区及周边地区18个气象站1960—2015年共56年的降水资料,采用标准化降水指数(SPI),运用游程理论和Mann-Kendall检验法分析了气象干旱时空演变特征,并进一步评估了三峡库区干旱致灾因子危险性。结果表明:(1)三峡库区年尺度的SPI值呈现平缓下降趋势,整体趋向全域干旱化,1989年为突变年;(2)各季节干旱站次比变化不大,总体呈缓慢上升趋势;夏、秋季干旱强度表现为上升趋势,春、冬季则相反;四季中,干旱强度和干旱站次比增幅最为显著的是秋季;干旱强度按冬、春、夏和秋季的顺序依次减小;(3)各季节SPI值存在明显的空间差异性,春季三峡库区东北部SPI值呈下降趋势,而西南部总体表现为不显著上升趋势,夏季则与春季相反;秋季全域化干旱趋势较为显著;冬季中西部SPI值呈不显著下降趋势,而东北地区呈现不显著上升趋势;(4)春、夏、秋季干旱频率较低的地区主要分布在三峡库区东北部,干旱频率较高地区则呈现显著的空间差异,冬季则相反;干旱频率大小随春、夏、秋和冬季逐渐增大;(5)三峡库区季尺度干旱危险性空间分布整体表现为中等和较低级别,春、夏季危险性等级总体处于中、低危险性,秋、冬季则整体呈现为中等危险性。秋、春、冬和夏季干旱致灾危险性依次递减。研究结果可为三峡库区水资源管理和干旱风险评估提供参考依据。

In recent years,the intensity and frequency of drought disasters in the Three Gorges Reservoir Area(TGRA)have shown an aggravating trend.Therefore,it is of great significance to identify the spatial-temporal characteristics of drought and the risk factors of drought.The precipitation data of 18 meteorological stations in the TGRA and surrounding area from 1960 to 2015 were used to analyze the spatial-temporal evolution characteristics of meteorological drought,and further evaluate the risk of drought disaster factors in the TGRA based on the standardized precipitation index(SPI),run theory,and Mann-Kendall test.The results showed that:(1)the annual SPI value in the TGRA indicated a slow downward trend,and the whole area tended to be arid,with an abrupt change point in 1989;(2)there was not significant change in drought station ratio in each season,and it showed a slowly increasing trend in general;the drought intensity in summer and autumn showed an upward trend,while it was the opposite in spring and winter;among the four seasons,the most significant increase of drought intensity and drought station ratio was autumn;the drought intensity decreased in the order:winter>spring>summer>autumn;(3)the SPI value of each season had obvious spatial difference;in spring,the SPI value in the northeast area of the TGRA showed a decreasing trend,while the SPI value in the southwest of TGRA exhibited an insignificant increasing trend;the SPI value in summer was the opposite of that trend in spring;in autumn,drying trend was more significant in almost the entire TGRA;in winter,the SPI value in the mid-west of the TGRA showed an insignificant decline,while those in the northeast of TGRA presented an insignificant increase;(4)the areas with low drought frequency in spring,summer and autumn mainly distributed in the northeast of the TGRA,while the areas with high drought frequency showed significant spatial differences;the spatial distribution of drought frequency in winter was opposite to that in other seasons;the drought frequency increased gradually in the sequence:springspring>winter>summer.These results can provide reference for water resources management and drought risk assessment in the TGRA.