湖南气象干旱日数的时空变化特征

利用湖南88个地面气象站点1960-2009年逐日资料,按照国家标准《气象干旱等级GB/T 20481-2006》中推荐使用的综合气象干旱指数（CI）,采用EOF、REOF和Morlet小波分析等方法,统计分析了1960-2009年湖南气象干旱日数的时空变化特征。结果表明：湖南年平均气象干旱日数呈南多北少的分布特点,高值区位于湘江中上游地区。湘江中上游、常德西北部至怀化一带为轻旱日数相对高值区;中旱日数偏多中心为湘中、湘南北部、湘北部分地区;湘中以南、湘北、湘西为重旱日数偏多区域;湘中衡邵盆地为特旱日数大值中心。EOF和REOF分析表明,湖南气象干旱日数空间分布既有全区一致性,也存在南部与北部、东北与西南相反变化的差异,空间分布大致可分为湘南、湘东北、湘西北、湘西和湘中5个气候区。近50a各气候区气象干旱日数变化趋势均不显著,气象干旱日数的年际变化幅度均较大,但进入21世纪后,除湘西区气象干旱日数有减少趋势外,其余4个气候区均呈增多趋势。Morlet小波功率谱分析表明,气象干旱日数存在2~3a、4~6a的显著性周期变化。研究结果可为湖南制定合理的抗旱对策提供科学依据。

Spatial and Temporal Variation of Meteorological Drought Days in Hunan Province

The spatial and temporal distribution of meteorological drought days was analyzed by using of Empirical Orthogonal Function（EOF）, Rotated Empirical Orthogonal Function （REOF）and wavelet analysis methods, based on daily meteorological data from 88 meteorological stations in Hunan province from 1960 to 2009, according to Comprehensive Meteorological Drought Index（CI） recommended by Classification of Meteorological Drought Category of GB/T 20481 -2006. The results showed that total meteorological drought days in southern Hunan were more than that of in northern Hunan. There were high value areas with the number of slight meteorological drought days in the upper and middle reaches of Xiangjiang river, northwest of Changde to Huaihua. The moderate meteorological drought days were in the central, north of southern Hunan and northern Hunan. However, the severe meteorological drought days were in the central, southern, northern and western Hunan. The center of extreme meteorological drought days was in the Hengshao Basin. The spatial distribution of meteorological drought days was classified into five climatic types in whole province,including south Hunan, northeast, northwest, west and central Hunan, according to EOF and REOF analysis. Meteorological drought days were not significant change in all climatic types in last 50 years, but they had an obvious inter-annual variability. Meteorological drought days in the west Hunan have decreased since the beginning of 21＂ century, but those in other four climate types have increased. There was an obvious periods of 2 - 3years and 4 - 6years according to Morlet wavelet analysis. The results could provide the scientific basis for drought resistant countermeasures in Hunan province.