中国西部湖泊水量对未来气候变化的响应--蒙特卡罗概率法在气候模拟输出的应用

基于CGCM2对未来100年气候的9个模拟试验,对中国半干旱地区青海湖、岱海和呼伦湖及其流域,运用蒙特卡罗分析法模拟湖泊水量对气候变化的响应以及相应的概率.结果表明,从2020s,2050s和2080s三个时期温度增加的发生频率高于75%的分布看,温度将稳定增加2-5℃.未来的年平均温度增幅将超过了过去50年的观测记录,与过去一万年期间高温期的变化幅度相当.三个时期75%以上发生频率的温度和降水变化将会分别引起青海湖流域为-5%至 10%,呼伦湖流域为-7%至 5%,岱海流域为 2%至 12%的降水变化.虽然未来年降水总量的变幅没有超过过去50年器测记录变幅,更不及全新世的降水变化量,但湖泊水量对气候变化的反映变率较变幅要大.模拟的气候变化在75%概率的情况下,未来3个湖泊水量将有累计30%-45%的变化,变幅在±10%之间.快速的湖泊水量变化不能不引起对不远未来的水资源状况的重视和警备.     

On the influence of the grain size distribution curve on P-wave velocity,constrained elastic modulus Mmax and Poisson's ratio of quartz sands

The paper presents an experimental study on the influence of the grain size distribution curve on dynamic soil properties. More than 160 resonant column tests with additional P-wave measurements have been performed on 27 different grain size distribution curves of a quartz sand. While the small-strain shear modulus G_max has been discussed by Wichtmann and Triantafyllidis [1] the present paper focusses on P-wave velocity v_P, on the small-strain constrained elastic modulus M_max and on Poisson's ratio ν$\nu$. It is demonstrated that while v_P and M_max do not significantly depend on mean grain size d₅₀ in the investigated range, they decrease with increasing coefficient of uniformity C_u=d₆₀/d₁₀ of the grain size distribution curve. Poisson's ratio does also not depend on d₅₀ but increases with increasing C_u. An empirical formula similar to Hardin's equation has been developed for M_max, considering the influence of the grain size distribution curve. It predicts quite well the experimental data.