近60多年来滇池流域干旱特性及重现期分析

根据滇池流域3个气象站、3个水文站、2个水位站、14个水库站建站(1950 s)至2014年的逐月(日)气象、水文观测系列,采用标准化降水指数(SPI)、标准化径流指数(SRI)以及干湿指数(Ia)三类干旱指标,按游程理论识别干旱事件、确定干旱历时和干旱烈度两个特征变量;通过小波分析揭示干旱历时和烈度的周期性规律;运用Gumbel Copula函数构建干旱历时和烈度的联合分布,计算干旱联合、同现重现期,及前一场干旱影响下的后一场干旱发生的条件重现期。结果表明,滇池流域干旱趋于严重;气象、水文、农业3类干旱的干旱历时或烈度,均具有100年以上变化周期;近期的干旱(2012-02~2013-04)为1950 s以来最严重干旱,联合、同现重现期分别达120.48和224.41 a,受上一场特大干旱(2009-05~2010-03)的影响,条件重现期高达271.82 a,持续干旱的叠加效应加剧了旱情和灾害程度。从滇池水位变化、区域大气环流异常、三类干旱规律、干旱史料文献及湖泊沉积物等多方面对比分析,印证了成果的科学合理性。

RETURN PERIOD OF DROUGHT IN DIANCHI BASIN IN LAST 60 YEARS

Meteorological and hydrological monthly or daily data of 3 meteorological, 3 hydrological, 2 water level and 14 main reservoirs stations in Dianchi Basin from the 1950s to 2014 were collected and analyzed in this paper. First, based on meteorological hydrological and agricultural drought indices, namely SPI, SRI and I_a, drought events were identified and its duration and severity were confirmed through the Runs Theory. Then, the periodic variation regularity of drought duration and severity were revealed using wavelet analysis. Finally, multivariate joint distribution of drought duration and severity was constructed through the Gumbel Copula function, joint and co-occurrence return periods of drought were calculated and conditional return period of one drought event by the influence of anterior drought event was determined. The results showed that in the whole basin, drought disaster was significantly worsening. There has an over 100 year variation period of no matter drought duration or drought severity. The drought in 2012-2013 was the mostly serious drought events and its joint and co-occurrence return periods were 120.48 and 224.41 years, respectively. Its conditional return period by the affection of drought in 2009-2010 was 271.82 years. When drought events were added up, there was an additive effect. Water level process of Dianchi Lake, abnormal region atmospheric circulation, drought historical documents and lake sediments were compared and analyzed, which prove the scientific reasonability of the research accomplishments.