为了减轻季节性干旱对四川省农业生产造成的影响，根据川中丘陵区8个气象站点1960-2011年的月降雨资料，基于标准降水指数（SPI）研究了该区季节性干旱时空分布特征，并分析了干旱成因。研究结果表明：对川中丘陵区影响较大的中旱、重旱及极旱主要集中在冬季和春季；近52 a来区内各站点的SPI值在9-11月呈下降趋势，宜宾在8-9月的SPI值显著下降（α=0.05）；区内四季SPI值的Hurst指数几乎都大于0.5，SPI值有很好的持续性；6月尺度（冬、春季）的SPI值显示出了5、11和28 a的周期，其中11 a的周期震荡最强，为第1周期。同时，一年四季中不同干旱等级的干旱频率也在不同地域上显示出了差异性。通过对月尺度SPI值和影响干旱的因素进行相关性分析，发现SPI与降水集中程度、日照时数呈极显著负相关（α=0.01），是影响川中丘陵区干旱的主要因素。该研究为四川省的防旱减灾提供参考。%In order to reduce the influence of seasonal drought on agricultural production in Sichuan Province, the standard precipitation index (SPI) was selected to describe drought characteristics based on monthly precipitation data from eight sites in the hilly area of central Sichuan during 1960-201. Mann Kendall rank correlation and the morlet wavelet method were applied to analyze the spatial and temporal distribution characteristics of seasonal drought, and the correlation analysis method was used to explore the causes of drought and propose drought prevention measures in the hilly area of central Sichuan. Results indicate that:moderate drought, severe drought, and extreme drought in the hilly area of central Sichuan, which influence this area seriously, mainly concentrated in winter and spring;Moderate drought mainly occurred in Spring (moderate drought frequency-17.3%), while severe and extreme drought mainly occurred in winter (severe and extreme drought frequency-11.5%). During the last 52 years, the SPI of each site increased in June and decreased from September to November, especially in Yibin, SPI were decreased significantly (α=0.05) in August and September, which may aggravate drought frequency and the category of hot-drought and autumn drought. Hurst of Spring SPI changes between 0.51(Suining) to 0.72 (Bazhong); Summer Hurst changes from 0.44 (Luzhou) to 0.72 (Daxian); Autumn Hurst varies from 0.49 (Neijiang) to 0.74 (Langzhong);Winter Hurst varies from 0.65 (Luzhou) to 0.81 (Langzhong);Almost all Hurst indexes of seasonal SPI in the region are greater than 0.5, which refers to good persistence on seasonal SPI, thus SPI features during nearly 52 years can be a reference for further drought research in this region. June scales (winter and spring) SPI value shows a cycle of 5, 11, and 28a, in which the strongest shock (11a) was the first cycle, 28a was the second cycle, and 5a was the third cycle. Actual drought conditions were consistent with change process of 11a scale wavelet real part. Drought frequency of drought category differs from regions;Moderate drought in spring and summer are mainly distributed in the central and northeastern sections of the hilly area of central Sichuan, such as Daxian and Gaoping. Otherwise, moderate drought in autumn and winter is mainly distributed in the southwestern part of the region, such as Neijiang. Severe and extreme seasonal drought always occurs in Suining and Yibin. Therefore, Suining and Yibin are the most important region for drought prevention. Correlation analysis was used to analyze relevance between monthly scale SPI and each meteorological factor (precipitation concentration degree was described by the ratio of daily maximum precipitation and monthly rainfall; temperature change with extreme maximum temperature and the average temperature difference to describe), which indicates that SPI was significant negatively correlated with precipitation concentration and sunshine hours (α=0.01), so precipitation concentration and sunshine hours are main factors affecting the drought of the hilly area of central Sichuan. Rainwater harvesting and utilization technology is an effective measure for improving rainwater use efficiency and preventing seasonal drought. This paper provides a reference for Sichuan drought mitigation.
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