澜沧江流域干旱气候变化特征及影响因素分析

基于澜沧江流域10个气象站1961～2010年逐日气象资料,利用Penman-Monteith模型计算了年、月湿润指数,并对其进行了标准化,统计了极端干旱事件发生的频率,进而采用Mann-Kendall趋势检验方法分析了澜沧江流域干旱气候变化特征及其影响因素。结果表明,从上游向中下游多年平均湿润指数逐渐增加,上游和中游的湿润指数呈增加趋势、下游呈下降趋势;自20世纪60年代至今,澜沧江流域经历了相对冷干-冷湿-冷干-暖湿-暖干五个阶段,暖干化趋势较为明显,其中冬季和春季为暖干化趋势最明显的季节;年降水量、湿润指数均在波动中呈下降趋势,气温和潜在蒸发量呈明显增加趋势,年降水量、湿润指数、气温和潜在蒸发量的变化倾向率分别为2.095mm/(10a)、0.006/(10a)、0.276℃/(10a)、6.231mm/(10a);澜沧江流域极端干旱事件频率在波动中呈减少趋势,下游呈上升趋势(上升速率为0.010 3次/a),20世纪60年代和21世纪初为澜沧江流域极端干旱事件频发的年代;降水量和日照时数为影响澜沧江流域极端干旱事件的主要气象要素。

Variations of Drought and Influencing Factors in Lancang River Basin

Based on the daily data of 10 meteorological stations in the Lancang River Basin from 1961 to 2010, the annual and monthly humid indexes are calculated by Penman-Monteith model with the extreme drought frequency. According to the calculated data, the spatial and temporal characteristics of the arid climate have been analyzed, as well as its impact factors. The results indicate that there is an obvious decreasing trend in annual precipitation and humid index, with the precipitation trend rate of 2.095 mm per 10a and the humid index 0.006 per 10a respectively; inversely, the annual temperature and potential evaporation have an increasing trend with the temperature trend rate of 0.276 degrees centigrade per 10a and the potential evaporation 6.231 mm per 10a; from 1961 to 2010,the Lancang River Basin experiences five stages, namely comparatively cold dry, cold humid, cold dry, warm humid and warm dry; it is extremely obvious in winter and spring;the average humid indexes gradually increase from upstream to downstream;the humid indexes in the upper-middle reaches show an increasing trend but it decreases in the down reaches;the frequency of extreme arid events declines from 1961 to 2010 in the Lancang River Basin while it increases in the lower reaches with the rate of 0.010 3 per year; in the 1960s, extreme arid events occurred frequently in the Lancang River Basin; the precipitation and sunshine durations were the key factors for affecting humid index.