澜沧江流域旱涝特征变化及其与季风之间的关联性研究

探讨澜沧江流域旱涝特征变化与季风之间的关联性,对于区域旱涝灾害的成因、机理和预测等重大科学问题的理解具有重要的意义。区域研究多侧重于揭示流域旱涝时空演变规律,而关于澜沧江流域的旱涝与季风的相互关系研究还较少。基于标准化降水指数(SPI12)、季风指数和水汽通量对澜沧江流域1957—2015年旱涝时空变化特征进行分析,探究澜沧江流域旱涝变化与季风指数的相互关系,并从水汽通量输送角度出发,进一步揭示季风对澜沧江流域旱涝变化影响的潜在驱动机制。研究结果表明:①流域旱涝特征具有明显的区域差异,下游区域是旱涝多发区;②流域干旱多于雨涝,且干旱频次在年和季节时间尺度上都呈现增加变化趋势;③澜沧江流域干旱和雨涝的频次主要存在3~5,8~15,20~25 a的3种周期性变化特征;④干旱和雨涝发生时段,南亚季风和高原季风指数与流域的SPI12指数相关性较强,受南亚季风和高原季风的输送距离影响,2种季风指数与SPI12指数的相互关系呈现区域差异性。研究结果有助于了解澜沧江流域旱涝时空变化特征,能够为防御旱涝灾害提供科学决策依据。

Changes in Characteristics of Drought/Flood and Its Connections with Monsoons in the Lancang River Basin

Studying the connections between drought/flood characteristics and monsoons in the Lancang River basin is of vital significance for understanding the causes, mechanisms and prediction of regional drought/flood disasters; yet the vast majority of existing studies are focused on the temporal and spatial evolution characteristics of drought/flood rather than on the connections between drought/flood characteristics and monsoons in the Lancang River basin. In this paper, the temporal and spatial changes in characteristics of drought/flood in 1957-2015 are investigated in terms of standard precipitation index (SPI12), monsoon index, and water vapor flux; the connections between drought/flood changes and monsoon index are examined, and the mechanism of drought/flood changes driven by monsoons and water vapor fluxes is further revealed. Results indicated that: (1) flood/drought has obvious regional difference, and the downstream area is prone to flood and drought; (2) the frequency of drought is superior to that of flood, showing an increasing trend in annual and seasonal time scales; (3) the frequencies of flood and drought mainly varied periodically at 3-5 years, 8-15 years, and 20-25 years; (4) in drought/flood period, indices of the South Asian monsoon and the Plateau monsoon have relatively strong correlations with the standard precipitation index (SPI12) in the Lancang River basin; such correlation varies in different regions due to the limited transportation distance of monsoons. The results are helpful in understanding the temporal and spatial change characteristics of drought/flood in the Lancang River basin, and also offer scientific basis for the decision-making of drought/flood prevention.