通过对洱海现代沉积物的精细采样，将放射性核素精确计年与沉积物粒度研究相结合，重建了600多年来洱海区域气候的干湿变迁，为恢复百年尺度的气候干湿变化提供了一条新途径。研究结果表明，15世纪是洱海地区最为湿润的一个世纪；洱海区域存在100a、200a两种时间尺度的气候干湿准周期波动；自19世纪末以来洱海区域气候整体上向干旱化方向发展，目前正处于干旱期末期，预计气候将由干旱转向湿润。%As a main lodging of surface substances, lake sediments continuously and sensitively record information of re-gional climate and environment with annual to decadal resolution. The sediment core EH911208 - 3 - 5 with alength of 83cm was taken from deepwater location in Erhai Lake in 1991, using the sediment - water interfacernsampler specially designed by ourselves. The sediments were cut at intervals of 0.5～1.0cm and were measured forgrain sizes by the Scanning Photo Sedimentograph "Analysette 20" made in Germany. Based on accurate dating by137Cs and 210Pbex, the author reconstructs the dry - humid transformation history of the regional climate accordingto the vertical profile of sediment particle sizes, which provides a new effective way for recovering the century-scale climatic changes. The following conclusions are drawn:rn (1) General environmental significance of sediment grain size should not be applied mechanically in recon-structing palaeoclimate. Only after concretely analyzing all the factors which affect sediment grain size, can credi-ble conclusions be obtained during discussing different time - scales climate changes.rn (2) During long time- scale studies, lake level is the most important factor dominating sediment grain size.Sediments are finer during the humid period of high water level because coarse particles can not be transported tothe lake's deepwater part. On the contrary, during short time- scale studies within a given climate period, rainfallchange in the drainage basin becomes the key factor determining sediment grain size because the lake level is basi-cally constant. When rainfall is heavy, runoff flow is strong enough to bring coarse terrestrial particles to the sam-pling location, resulting in larger grain sizes.rn (3) The 15th century was the driest in the region of Lake Erhai during the past 640 years. There exist twotime - scales( 100 and 200 years) climatic quasi - periodical changes. From the end of the last century, the regionalclimate has been becoming drier and drier as a whole. At present, it is at the end of the dry period, so the regionalrnclimate will become humid in near future.
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