一阶弹性波交错网格时间高阶差分格式及稳定性分析

弹性波模拟或逆时偏移时,对空间偏导数采用高阶差分格式可提高计算精度,但这种算法的稳定性条件过于严格,要求差分离散的时间步长必须足够小以确保算法稳定。在常规空间高阶差分格式的基础上,将速度(应力)对时间的高阶导数转化为不同精度的应力(速度)对空间的差分,得到了一种新的基于交错网格的时间高阶、空间高阶差分格式。通过对交错网格时间高阶差分格式稳定性的分析,认为该算法的稳定性条件较常规算法宽松,在弹性波场的求解过程中可以采用更大的时间步长。     

下滑坡及防治方案

下滑坡是由采煤引发的巨型深层顺层滑坡,目前处在蠕动变形阶段。本文对滑坡稳定性进行了计算,算出不同采空区面积下的稳定系数,计算了滑坡推力,提出了地表地下排水、煤层采空区设承重阻滑键、滑坡前缘设抗滑桩综合防治方案,可供防治设计施工参考。     

The numerical simulation on the PBL structure and its evolution over small-scale concave terrain

A high-resolution, nonhydrostatic, three-dimensional diagnostic PBL model over small-scale concave terrain was established in this paper. A two-dimensional prognostic model was developed based on the diagnostic model. The hydrostatic approximation was abandoned and the simple energy (E-ε) closure scheme was used in both mod-els. Using the two models, characteristics of PBL structure and its evolution were fully studied. The main characteris-tic of the PBL is the circulation, and it fairly affects the distribution of the pollutant in the pit.     

国家气象中心NWP新资料归档系统的技术特征

文章简要介绍了“八五”以来,国家气象中心数值预报系统新的归档方案设计特点、意义、内容,并探讨了归档软件开发中的一系列技术问题。     

High-order compact MacCormack scheme for two-dimensional compressible and non-hydrostatic equations of the atmosphere

This study is devoted to application of the fourth-order compact MacCormack scheme to spatial differencing of the conservative form of two-dimensional and non-hydrostatic equation of a dry atmosphere. To advance the solution in time a four-stage Runge–Kutta method is used. To perform the simulations, two test cases including evolution of a warm bubble and a cold bubble in a neutral atmosphere with open and rigid boundaries are employed. In addition, the second-order MacCormack and the standard fourth-order compact MacCormack schemes are used to perform the simulations. Qualitative and quantitative assessment of the numerical results for different test cases exhibit the superiority of the fourth-order compact MacCormack scheme on the second-order method.     

长时效的正压原始方程能量完全守恒(拟)谱模式

遵循误差反演补偿新计算原理,对正压原始方程传统气象全球拟谱模式方案进行了改造,构造了正压原始方程能量完全守恒全球拟增模式新计算方案,解决了正压原始方程的(非线性)计算稳定性问题和能量守恒整体性质保持问题,改进了相应正压原始方程传统气象全球拟谱模式方案的计算效能。新方案的数值试验表明:在计算实践上,新方案在解决能量守恒问题的同时,可解决(非线性)计算稳定性问题,并在一定条件下可解决非线性计算收敛性问题。进一步的比较数值试验还表明:在计算实践上,新方案具有在提高相应传统气象方案的计算精度,减少其计算量的同时,延长其计算时效,解决其中一类特定“气候漂移”问题方面的效用。本工作原理也适用于斜压原始方程情形。     

双参数云物理方案中谱形参数作用分析和数值模拟试验

云物理参数化方案中,各种粒子通常采用Г谱分布函数n(D)=N0Dαexp(-λD)。双参数方案中谱参数截距N0和斜率λ通过预报给出,谱形参数α设为固定值。为了讨论谱形参数的作用,理论上分析了谱形参数取值对沉降过程和微物理源汇项的影响。利用MM5模式中增加的双参数显式云物理方案模拟了西北地区一次层状云降水过程,模拟针对雨滴谱的谱形参数rα不同取值分别做了试验。模拟结果基本符合理论分析,谱形参数rα变化时模拟出的地面降水和云的宏微观特征有差异。     

酒店气象专用电视频道技术方案

阐述了酒店气象专用电视频道的工作原理,同时还推荐了本系统软硬件具体的配置,最后对专用系统软件的工作流程及其使用方法进行了详细的说明。     

植被动力学模式中物候方案的研究进展

植物物候是指植物生长过程中呈现出的季节性现象,一般与植物所处的气候与环境变化密切相关。植被动力学模式研究的物候主要表现为叶面积指数变化,直接影响陆气间的碳通量与水热交换,同时影响物种间的竞争,从而间接地影响生态系统的结构组成。按照建模方法的差别,目前模式中使用的物候方案可分为使用卫星观测资料的物候方案、基于物候——气候关系的统计模型和基于叶碳平衡(周转)的动力学模型三大类。将植物物候分为物候期的触发和物候期叶片的发育过程两部分,分别对国际上广泛使用的八种全球植被动力学模式进行分类描述,对比其优缺点。最后探讨了植被动力学模式中物候方案的进一步发展方向。     

An improvement of the mass flux convection parameterization scheme and its sensitivity tests for seasonal prediction over China

A modified cumulus parameterization scheme, suitable for use in a seasonal forecast model, is presented. This parameterization scheme is an improvement of the mass flux convection scheme developed by Gregory and Rowntree (1989; 1990). This convection scheme uses a “bulk” cloud model to present an ensemble of convective clouds, and aims to represent shallow, deep, and mid-level convection. At present,this convection scheme is employed in the NCC T63L20 model (National Climate Center, China Meteorological Administration). Simulation results with this scheme have revealed some deficiencies in the scheme,although to some extent, it improves the accuracy of the simulation. In order to alleviate the deficiencies and reflect the effect of cumulus convection in the actual atmosphere, the scheme is modified and improved.The improvements include (i) the full estimation of the effects of the large-scale convergence in the lower layer upon cumulus convection, (ii) the revision of the initial convective mass flux, and (iii) the regulation of convective-scale downdrafts. A comparison of the results obtained by using the original model and the modified one shows that the improvement and modification of the original convection scheme is successful in simulating the precipitation and general circulation field, because the modified scheme provides a good simulation of the main features of seasonal precipitation in China, and an analysis of the anomaly correlation eoetfieient between the simulation and the observations confirms the improved results.