【摘要】 极端降水事件是气候变化的一个重要方面。澜沧江流域纵贯13个纬度,最大相对高差近5000 m,跨6种气候带,是全球少见的南北向大江,它在气候、水文、地理、生态学等多方面都具有重要的科学研究价值。自1960年以来,流域经历了显著的气温上升。探讨在气候变暖背景下这一复杂流域的极端降水变化具有重要意义。本文利用澜沧江流域及其周边35个气象站1961-2005年的日降水资料,分析了小于5 mm、5～10 mm、10～50 mm以及大于50 mm 4个不同量级降水的降水量、降水日数和日平均降水强度的变化趋势。并计算了每种量级降水占总降水量的百分比及降水频率。结果表明,各量级各项指标均存在明显的区域变化特征,流域总体上极端降水频率的增加态势明显。对典型地区站点分析表明,极端降水的增加可能与气候系统随机性变强有关。更多还原

【Abstract】 Extreme precipitation is an important aspect of climate change.According to the estimation using the latest climate models,the extreme precipitation events will become frequent in a warming world.Significant increases of the very heavy precipitation and decreases of light and moderate precipitations have indeed been observed over most land areas of the globe in the last few decades.The Lancang River,with a relative altitude difference of about 5000 m,flows through 13 latitudes and 6 climatic zones.It is rarely seen in the world and has important scientific values for climatology,hydrology,geography and ecology.Since 1960,the basin has experi-enced a significant increase in temperature like most parts of the world.Studying the changes of extreme precipi-tation events in the basin in the context of global warming is of great importance.Based on a daily precipitation dataset of 35 meteorological observation stations distributed in and around the Lancang River basin,trends of precipitation amounts,precipitation days and daily precipitation intensity during a 45-year period(1961-2005) of 4 different classes ranging from less than 5,5-10,10-50 and larger than 50 mm were analyzed,and the precipitation frequency and the proportion of precipitation amount of each precipitation class were calculated.The result showed that all the indexes varied spatially,and for the basin as a whole,the frequency of the extreme events increased obviously.Analysis of a typical station indicated that the increase of extreme precipitation and the randomness of the climatic system might be closely related with each other.更多还原