长江流域1961~2015年不同等级干旱时空变化分析

分析长江流域历史时期的干旱时空变化特征，对于目前和未来的干旱应对具有重要参考价值。采用12月尺度标准化降水指数（SPI_12）对长江流域134个气象站1961~2015年逐日降水数据进行统计分析，探究了流域内不同等级干旱的时间变化特征和空间分布格局。结果表明：长江流域每年发生干旱的平均次数和站点数均没有明显变化趋势，但特旱发生次数和站点数均呈升高趋势；流域内各站点发生干旱的频率主要介于30%~35%之间，四川盆地、云南省北部、贵州省北部发生干旱的频率大多呈增加趋势，其他地区干旱发生频率以降低趋势为主。上述结果表明，长江流域不同等级干旱呈现不一致的时间变化特征，发生特旱的风险呈增加趋势，不同区域的干旱变化趋势也存在显著差异，因此需要分区制定针对性的应对措施。

Temporal and spatial variation characteristics of different drought grades from 1961 to 2015 in Yangtze River Basin

Analyzing temporal and spatial variation characteristics of droughts in historical period in the Yangtze River Basin has important reference significance for the present and future drought fighting. In this paper, 12-month standard precipitation index (SPI_12) was used to analyze the daily precipitation data of 134 weather stations in the Yangtze River Basin from 1961 to 2015 to explore the temporal variation trends and spatial distribution patterns of different drought grades in the watershed. The results showed that: there was no obvious change in the average annual drought frequency and the site number in the Yangtze River Basin, but the frequency of extreme drought and the site number increased. The drought frequency in the whole watershed was mainly between 30% and 35%, showing increasing tendency in Sichuan Basin, northern Yunnan Province and northern Guizhou Province, and a downward tendency in other areas. The above results indicate that temporal characteristics of different drought grades are inconsistent in the Yangtze River Basin, and the risk of extreme drought is increasing. The drought trends in different regions are also significant different, therefore zoning is essential to develop targeted countermeasures.