小流域水分行为、生态效应及其优化调控研究方面的若干问题

把小流域水文生态研究,分解为小流域水分行为、生态效应及其优化调控研究3个方面。在分析国内外研究现状与问题的基础上,指出了其需要系统加以探讨的若干内容,认为由此可构建流域水文生态学的基本框架,进而发展流域水文生态学。     

一定分布模式下的最优Lp估计

观测数据在一定的分布模式下,需从理论上解决究竟用多大的ｐ值进行Ｌｐ估计（最优ｐ值的确定）,本文基于渐近方差整体最小的原则,给出了最优Ｌｐ估计的定义。观测数据中含有粗差（异常值）的扰动,其误差分布可视为污染分布,作者分析了最优ｐ值的大小,结果表明,若观测数据中含有不同大小、数量的粗差,为使Ｌｐ估计差最小,则ｐ将取［１．２,１．５］中的某一定值,Ｌｐ估计结果最优,此结论对测量数据处理具有一定的参考价值     

一种卫星重力梯度数据的ARMA最优滤波模型构建方法

由于卫星重力梯度观测的有色噪声特性和海量观测特征,在利用直接法进行重力场模型的最小二乘求解时,观测值的协方差阵为超大型的非对角阵,这给数值求解带来了极大困难.本文提出了一种基于先验误差功率谱密度的最优ARMA滤波模型构建方法,结合法方程的分块求解策略,可实现对卫星重力梯度观测值的高效滤波处理.数值仿真结果表明,利用最优ARMA滤波器进行时域滤波后,法方程的态性得到了明显改善,重力梯度观测值中的有色噪声得到了有效的"白化"处理,大地水准面精度得到了显著提升.     

南北地震带南段地壳厚度重震联合最优化反演

重力反演方法是研究地壳结构和物性界面起伏的有效地球物理手段之一.本文收集了南北地震带南段67个已有的固定台站接收函数反演的Moho面深度结果,并使用基于EGM2008重力异常模型计算的布格重力异常,验证了本文提出的重震联合密度界面反演方法的有效性.利用接收函数对台站下方Moho面深度估计作为先验约束,定义了一类评价函数,通过对重力反演算法中尺度因子,平移因子和稳定性因子的最优选择,最小化重力反演结果与接收函数模型之间的差异.结果表明,本文提出的方法,可以有效地同化不同地球物理方法获得的反演模型,且通过重震联合反演可以改进由于对空间分布不均匀的接收函数结果插值可能而引起的误差.本文还通过引入Crust1.0的Moho面深度为初值,同时考虑地壳密度的横向不均匀分布,通过模型之间的联合反演有效改善了地球物理反演模型间的不一致性问题.本文反演得到的最优化Moho面深度模型与已知67个台站位置接收函数模型之间的标准差约1.9km,小于Crust1.0与接收函数结果模型之间标准差为3.73km的统计结果.本文研究结果对于同化重震反演结果、精化地壳密度界面模型,都具有十分重要的参考意义.     

公众气象服务支付意愿影响因素研究

基于中国气象局2008年调查数据,运用二分Logistic回归、最优尺度回归和判定树CRT模型分析了公众气象服务支付意愿的影响因素。结果表明：个体因素中年龄与文化程度对公众气象服务支付意愿（包括是否支付与支付多少）有显著影响,而性别因素只对支付多少有显著影响,对是否支付没有显著影响;收入因素对公众气象服务支付意愿有显著影响;关注程度、天气预报准确性、天气预报及时性、气象服务总体满意度对公众气象服务支付数额多少有显著影响,但影响程度很小;个体因素与收入因素对公众气象服务支付意愿影响程度较高,而心理因素影响程度很小。     

Optimization Research of Water-Soil Resources in Huanghua

According to the present situation and problems of land use in Huanghua, this article determines the objectives of optimal allocation of land resources. As the basis of gray linear programming approach, we create gray linear programming model and set decision variables. By constructing the objective function and collection of constraint equations in which the main constraints is water resources, we obtain the program of optimal allocation of land resources under different constraints of water resources. The optimal result is analyzed to the present situation and planning of land use, to study feasibility of the program and the effectiveness in the decision of sustainable use of water -soil resources     

Observations of submesoscale eddies using high-frequency radar-derived kinematic and dynamic quantities

The spatio-temporal variability of submesoscale eddies off southern San Diego is investigated with two-year observations of subinertial surface currents [O(1) m depth] derived from shore-based high-frequency radars. The kinematic and dynamic quantities — velocity potential, stream function, divergence, vorticity, and deformation rates — are directly estimated from radial velocity maps using optimal interpolation. For eddy detection, the winding-angle approach based on flow geometry is applied to the calculated stream function. A cluster of nearly enclosed streamlines with persistent vorticity in time is identified as an eddy. About 700 eddies were detected for each rotation (clockwise and counter-clockwise). The two rotations show similar statistics with diameters in the range of 5–25 km and Rossby number of 0.2–2. They persist for 1–7 days with weak seasonality and migrate with a translation speed of 4–15 cm s⁻¹ advected by background currents. The horizontal structure of eddies exhibits nearly symmetric tangential velocity with a maximum at the defined radius of the eddy, non-zero radial velocity due to background flows, and Gaussian vorticity with the highest value at the center. In contrast divergence has no consistent spatial shape. Two episodic events are presented with other in situ data (subsurface current and temperature profiles, and local winds) as an example of frontal-scale secondary circulation associated with drifting submesoscale eddies.     

On the growth of disturbances to forced and dissipated barotropic flows

Abstract

We consider the growth of disturbances to large-scale zonally-asymmetric steady states in a truncated spectral model for forced and dissipated barotropic flow. A variant of the energy method is developed to optimize the instantaneous disturbance energy growth rate. The method involves solving a matrix eigenvalue problem amenable to standard numerical techniques. Two applications are discussed. (1) The global stability of a family of steady states is assessed in terms of the Ekman damping coefficient r. It is shown that monotonic global stability (i.e., every disturbances energy monotonically decays to zero) prevails when r≥r_c . (2) Initially fastest-growing disturbances are constructed in the r<r_c regime. Particular attention is paid to a subregion of the r<r_c regime where initially-growing disturbances exist despite stability with respect to normal modes. Nonlinear time-dependent simulations are performed in order to appraise the time evolution of various disturbances.     

Optimum design of stone column-improved soft soil using multiobjective optimization technique

A combined simulation–optimization-based methodology is proposed to identify the optimal design parameters for granular bed–stone column-improved soft soil. The methodology combines a finite difference-based simulation model and an evolutionary multiobjective optimization model. A combined simulation–optimization methodology is developed for two different formulations: (a) the minimization of maximum settlement and the minimization of differential settlement subject to stress constraints; (b) the minimization of maximum settlement, the minimization of differential settlement and the maximization of the degree of consolidation subject to stress constraints. The developed methodology is applied to an illustrative system. Different scenarios are evaluated to examine critical field conditions. The solution results show that the modular ratio and the ultimate stress carrying capacity of the stone column are the most important parameters for optimal design. The obtained results also show the potential applicability of the developed methodology.