<正>观测资料显示，1951—2000年长江三角洲年降水和极端降水年际差异较大，但没有呈现显著线性变化趋势。利用EcHAM5/MPI-OM模式与实测降水数据比较发现，该模型能较好的模拟年降水和极端降水变化。2001-2050年，IPC（：3种不同c0，排放情景下，年降水与极端降水变化并不一致，年降水都出现明显的下降趋势，但极端降水却增加显著，尤其中等排放情景下，2020s年代年降水量锐减，但极端降水迅速增加，说明未来长江三角洲洪涝和干旱发生的几率更高，极端气候造成的危害将更严重。

According to the theory of tensile and composite, prestressing mechanical model of twisted bamboo bundle is introduced. Horizontal shear strength and bending properties of three kinds of laminated veneer lumber (LVL) i.e. wood laminated veneer lumber, wood-bamboo LVL and wood-twisted bamboo bundle LVL are tested. The results show horizontal shear strength has no obvious difference among those three composites. However, the bending properties of wood-bamboo laminated veneer lumber has an obvious increase of MOE and MOR, at 22.8% and 18.6% respectively, compared with that of wood LVL without bamboo. Wood-twisted bamboo bundle laminated veneer lumber has 17.6% increase of MOE and 11.0% increase of MOR, compared with wood-bamboo LVL. The existence of prestressing effect of twisted bamboo bundle can improve its bending properties. Therefore, prestressing effect of twisted bamboo buddle is positive.