1961～2010年金沙江流域降水时空演变特征

基于金沙江流域1961~2010年逐日降水资料,对流域长时间尺度降水要素和多个典型降水日数进行分析,研究金沙江流域降水的时空演变特征。结果表明:1961~2010年,金沙江流域年降水量呈一定的增加趋势,但未通过显著性检验,汛期雨量变化趋势不明显,逐月降水除9月和12月外其他月份均呈微弱增加趋势。小雨等级和中雨等级的降水日数空间变化趋势相似,呈中上游地区微弱增加、下游地区微弱减少趋势,大雨及以上等级的降水日数则以微弱增加为主,仅在源区、德格一带呈不明显减少趋势。年无雨日数和年连续无雨日数呈比较明显的中上游地区减少、下游增加趋势,特别是年无雨日数在昭觉、昭通、会泽等区域增加趋势显著,年连续有雨日数则呈全流域减少,在下游小部分地区显著减少。研究还表明金沙江流域下游地区无雨日数及连续无雨日数特别在2000s偏多,而年连续有雨日数则在2000s明显偏少,表明近年来流域下游地区发生干旱事件的可能性增加。

TEMPORAL AND SPATIAL VARIATIONS OF PRECIPITATION IN JINSHAJIANG RIVER BASIN DURING 1961-2010

To study temporal and spatial variations of precipitation in Jinshajiang River basin, some typical precipitation indices on long time scale and some typical rainy days were analyzed in present research, by applying the Mann Kendall test and Empirical Orthogonal Function method based on daily precipitation data during 1961-2010 in Jinshajiang River basin. The results shows that annual areal rainfall had a certain increasing tendency without passing the significance test, while annual rainfall in the lower reach of the basin decreased weakly. Precipitation in the flood season had no obvious changes, while monthly rainfall through a year (except rainfall in September and December) had a weak increasing tendency. In addition, annual rainfall showed obvious spatial differences, and the higher rainfall area is located in the lower basin especially in Hengduan Mountain area. Rainfall in the flood season showed more obvious regional characteristics, and the higher value area is also located in Hengduan Mountain area. At the same time, rainy days for light level and moderate level increased weakly in the upper and middle regions, while they decreased weakly in the lower basin, without passing the significance test. Rainy days for heavy rain grade increased in the most of the whole basin, but it had unobvious decreasing tendency in the head region and around Dege station without passing the significance test. The number of no rain days and the number of consecutive no rain days in one year showed the similar spatial change patterns and had obvious decreasing tendency in the upper and middle basin, while they had obvious increasing tendency in the lower basin, especially that the number of no rain days in one year increased dramatically around Zhaojue, Zhaotong and Huize stations with passing the significance test. However, the number of consecutive rainy days in one year almost decreased in the whole basin, and decreased significantly in a small part of the lower basin. Moreover, as far as decadal changes were concerned, the number of no rain days and the number of consecutive no rain days in one year were the biggest in 2000s, while the number of consecutive rainy days was the smallest in 2000s, which was consistent the recent frequent occurrences of drought events in West South China. The temporal changes of the typical precipitation indices may confirm the possible increasing tendency for occurrence of drought events in the downstream of Jinshajiang River basin