怒江流域下游地区气象与水文干旱特征研究

A Study on the Characteristics of Hydrological and Meteorological Droughts in the Lower Nu River

以怒江下游勐波罗河流域为例,利用周边气象站点年的月降水量、月气温和流域出口水文站月径流数据,计算气象干旱指标标准化降水指数(SPI)、标准化降水蒸散指数(SPEI)和径流干旱指数(SDI),分析该地区1966-2013年间不同参考期(12个月、6个月和3个月)的气象和水文干旱变化过程,揭示流域水文干旱与气象干旱发生的关联。研究结果表明,自21世纪初期以来,流域各参考期干旱指数呈现减少趋势(干旱增加),尤其是SPEI-6M (参考期为6个月的SPEI)和SPEI-3M (参考期为3个月的SPEI)。研究区气象与径流干旱均具有多尺度周期性特征:在20世纪90年代中期之后,25~30年大尺度周期的等值线中心逐渐下移,时间尺度缩短为10~15年。进入21世纪以来,径流干旱在25年以上的大尺度上演变为减弱的干旱期,在10~15年中尺度上则处于由干旱向微湿润变化的过渡期。径流干旱与气象干旱关系密切,通过气象干旱指数SPEI-6M,可以较好地预测年径流干旱变化程度。

Taken Mengboluo River, the major tributary in the lower reaches of Nu River as a case, the standard precipitation index (SPI), the standardized precipitation evapotranspiration index (SPEI) and the runoff drought index (SDI) were employed to analyse the change processes of meteorological and hydrological drought based on the monthly precipitation and temperature data of the surrounding meteorological stations from 1966 to 2013, and the monthly runoff of the outlet of the river. The drought indexes value in three reference periods (12 months, 6 months and 3 months) were calculated for each indexes, and the correlation between meteorological and hydrological drought in the basin were also analysed. The results show that there were increasing drought trend, especially, that represented by SPEI-6M and SPEI-3M since 2000s;the drought occurred with multi-scale periodic characteristics. After the mid-90s, the large-scale 25–30 years periodicity gradually moved down to the 10–15 years periodicity. After 2000s, the runoff drought has changed into a weakened drought period over 25 years;but on the mesoscale periodicity with 10–15 years, it is in a transition period from drought to semi humid. Runoff drought is closely related to meteorological drought. Meteorological drought index SPEI-6M could be used to predict annual runoff drought.