气候重建工作的深入开展极大地促进了全新世亚洲季风变化的研究,然而当前重建结果对亚洲季风的演变特征和机理存在很大争议,开展古气候模拟对理解全新世亚洲季风演变的时空特征和成因机制具有重要意义。为此,本文主要从气候模式模拟的角度回顾全新世亚洲季风百年-千年尺度变化的模拟研究工作,并将从外强迫和气候系统内部变率这两个角度对机制进行探讨。主要有以下进展:全新世瞬变模拟试验结果反映早全新世以来亚洲季风降水呈下降趋势,这主要受到地球轨道参数的影响,并通过改变海陆热力差异和半球间温度梯度来影响亚洲季风降水。在百年尺度弱季风事件上,模拟的8.2 ka BP时期的亚洲季风弱事件主要是由冰川融水触发,引起大西洋经向翻转环流AMOC减弱并通过大气遥相关导致季风降水减少;而4.2 ka BP时期模式模拟的亚洲弱季风事件主要是受内部变率所主导而并非外强迫因子影响。亚洲季风百年尺度变化的模拟研究主要集中在过去2 000年时段,中世纪气候异常期季风明显增强,而在小冰期逐渐减弱,太阳辐射和火山活动是影响其变化的主导因子,它们通过影响海陆热力差异、印—太海温变化来影响季风变化。
The trust region(TR) method for optimization is a class of effective *** conic model can be regarded as a generalized quadratic model and it possesses the good convergence properties of the quadratic model near the **...
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The trust region(TR) method for optimization is a class of effective *** conic model can be regarded as a generalized quadratic model and it possesses the good convergence properties of the quadratic model near the *** Barzilai and Borwein(BB) gradient method is also an effective method,it can be used for solving large scale optimization problems to avoid the expensive computation and storage of *** addition,the BB stepsize is easy to determine without large computational *** this paper,based on the conic trust region framework,we employ the generalized BB stepsize,and propose a new nonmonotone adaptive trust region method based on simple conic model for large scale unconstrained *** traditional conic model,the Hessian approximation is an scalar matrix based on the generalized BB stepsize,which resulting a simple conic *** adding the nonmonotone technique and adaptive technique to the simple conic model,the new method needs less storage location and converges *** global convergence of the algorithm is established under certain *** results indicate that the new method is effective and attractive for large scale unconstrained optimization problems.
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