Modelling of meteorological conditions at an urban scale for the PUMA winter campaign

For the winter 2000 campaign of the Pollution of Urban Midlands Atmosphere project, observation and numerical modelling of meteorological conditions over the West Midlands conurbation, UK, was undertaken. Modelling was performed using the regional atmospheric meteorological system (RAMS). This paper presents a comparison of modelled and observed wind and temperature for 25 and 26 January 2000. The RAMS model uses two nested grids with a mesh size of 2 km for the inner grid which is embedded in the outer grid with a mesh size of 8 km. Statistical evaluation of the model results against the observational data of wind speed, direction and temperature at 10 m was conducted. In general, the modelling results are in a reasonable agreement with observation. The statistical evaluation suggests that model performance is poorer for the inner grid than the outer grid as the model uncertainties (mainly mean bias) transfer from the outer to inner one. The low indices of agreement of temperature and wind are mainly associated with the systematic root-mean-square-difference values. For temperature, the systematic bias may also be affected by representation of cloud amount by the model. For wind, the model tends to have a poor performance for calm conditions, as under a stable anti-cyclonic situation local wind patterns associated with topography may develop, although the topography of the region is relatively flat. The results for the inner grid reveal some subtle spatial patterns at a scale smaller than 10 km near hills and valleys with differences in elevation of a few hundred metres.     

Development and testing of numerical methods for two-way nested air pollution modelling

A new 3-D model REGINA (REGIonal high resolutioN Air pollution model) is under development at the National Environmental Research Institute (NERI). The model is based on pieces from several models developed over the last decades at NERI. The aim of the work is to develop a nested model which can operate with very high resolution in both space and time. To fulfill this aim the choice and implementation of accurate numerical methods is crucial. The model will be applied for studying air pollution phenomena (both monitoring, forecasting and scenarios) over Denmark. The present paper is focussed on the modification, implementation and testing of a numerical method for treating the horizontal advection in the model as well as the implementation of two-way nesting techniques. The horizontal transport in the model is solved using an accurate space derivative algorithm. This method is traditionally implemented with periodic boundary conditions, however, this is not an option for nested modelling. A new method for calculating non-periodic boundary conditions has been developed in order to overcome this problem. Extensive testing of the numerical solution of the advection and the coupling of the solution of advection and chemistry in the model using Molenkamp–Crowley rotation tests have been carried out. The results show that the model with the current implementation of numerical methods is suitable for calculating air pollution levels with high resolution.     

用ANSYS模拟结构-地基动力相互作用振动台试验的建模方法

本文以结构－地基动力相互作用振动台模型试验为基础，结合通用有限元软件ANSYS，对结构－地基动力相互作用体系进行有限元计算建模的一些问题作了研究，主要包括柔性土容器的模拟、土体动力本构模型的选用、土体与结构交界面上的状态非线性模型、网格划分、重力的考虑、结构中钢筋的处理以及对称性的应用等。文中给出了利用上述建模方法对结构－地基动力相互作用体系进行计算的一些加速度时程结果，并与试验结果相对照，吻合较好。通过计算分析，验证了简化处理方法的合理性和计算模型的可行性。     

基于GTP的地下工程与围岩一体化真三维空间构模

针对地下工程开挖体的基本特征及其真三维建模要求，在广义三棱柱(GTP)模型的基础上进行扩展，提出采用E—GTP模型来构建地下工程开挖体的真三维模型。通过与其围岩地质体的G—GTP模型的耦合，实现了基于GTP的工程开挖体与围岩地质体的一体化建模。该模型将地下三维空间实体抽象为点、线、面、体四类对象，通过结点、TIN边、侧边、TIN面、侧面和GTP体元共6个基本几何元素进行统一表达。该文重点讨论了E—GTP的建模原理与方法，并介绍了基于面向对象思想的一体化空间数据结构。     

我国入境旅游的特点和发展趋势分析

入境旅游人数以及旅游(外汇)收入是衡量一个国家旅游实力和开放程度的重要指标。本文在回顾中国入境旅游发展历史的基础上，通过对我国20多年入境旅游方面有关指标的分析总结了我国入境旅游具有增长的持续性、波动性和阶段性，入境旅游发展的脆弱性和集中性等特点。针对入境旅游未来的发展趋势提出加快我国入境旅游发展的建议。     

原子荧光光谱法测定地球化学样品中的砷、锑和汞的方法改进

在原子荧光光谱法中，通过改进地球化学样品的分解条件，预还原条件及测定条件，使砷、锑和汞能在同一介质中测定，而且实现了砷与汞的双道同时测定。方法的检测出限、准确度及精密度均能达到行业要求。     

b值在地震预测中的三类应用及其物理基础与须注意的问题

将b值在地震预测中的直接应用归为三类：1）根据b值的动态变化预测地震。2）根据G－R律求出各级地震平均复发周期或年均发生率，推测未来一定时段如50年或100年内发生各级地震的危险性。3）根据G－R直线在横轴的截距，预测强余震的震级。讨论了这三种用法的物理基础及现有工作中容易出现的问题。     

On the circulation in the East Frisian Wadden Sea: numerical modeling and data analysis

 In this paper we use a combination of numerical modeling and data analysis to gain a better understanding of the major characteristics of the circulation in the East Frisian Wadden Sea. In particular, we concentrate on the asymmetry of the tidal wave and its modulation in the coastal area, which results in a complex pattern of responses to the sea-level forcing from the North Sea. The numerical simulations are based on the 3-D primitive equation General Estuarine Transport Model (GETM) with a horizontal resolution of 200 m and terrain-following vertical coordinates. The model is forced at its open boundaries with sea-level data from an operational model for the German Bight (German Hydrographic Office). The validation data for our model simulations include time series of tidal gauge data and surface currents measured at a pile in the back-barrier basin of the Island Langeoog, as well as several ADCP transects in the Accumer Ee tidal inlet. Circulation and turbulence characteristics are investigated for typical situations driven by spring and neap tides, and the analysis is focused on dominating temporal and spatial patterns. By investigating the response of five back-barrier basins with rather different morphologies to external forcing, an attempt is made to elucidate the dominating physical balances controlling the circulation in the individual sub-basins. It is demonstrated that the friction at the seabed tends to slow down the tidal signal in the shallow water. This leads to the establishment of flood dominance in the shallow sea north of the barrier islands. South of the islands, where the water volume of the channels at low tide is smaller than the tidal prism, the asymmetry of the tidal signal is shifted towards ebb dominance, a feature which is particularly pronounced at spring tide. At the northern open boundary, the tidal wave propagating from west to east generates a sea-level difference of ∼1 m along the boundary, and thereby triggers vigorous alongshore currents. The frictional control in the model is located in the inlets, as well as along the northern boundary. The correlation between velocity and turbulent kinetic energy tends to the establishment of a net southward transport, giving theoretical support to the observed accumulation of sediments on the intertidal flats. Weak turbulence along the northern shores of the barrier islands and the small magnitude of the residual currents there promote accumulation of suspended matter in these areas, although wave action will generally counteract this effect. Received: 29 May 2002 / Accepted: 26 September 2002 Responsible Editor: Jean-Marie Beckers Acknowledgements We are indebted to S. Dick for providing the data from the operational model of BSH and to B. Flemming for the useful discussions. The topography data and Fig. 1 have been prepared in cooperation with F. Meyer. Figure 2 has been prepared by G. Brink-Spalink. We also thank for the comments from an anonymous reviewer which helped to improve our paper.     

观测有效性的度量方法

基于Hilbert空间理论 ,通过对观测方程的系数阵实施格拉姆_施密特 (Gram_Schmidt,G_S)正交化过程 ,分析观测的两个特性 ,从一个新的角度论证了参数估计的必要观测问题 ,以及多余观测与必要观测的关系 ;用欧氏范数‖·‖2 和Frobenius‖·‖ F 范数作为基本度量工具对观测提供参数估计的信息量进行度量分析 ,研究观测的有效性和参数估计的可靠性。采用观测空间分析方法研究了测绘学科中必要观测、多余观测等基本概念 ;提出了观测信息量、观测有效性的概念和相应的度量方法 ;从观测的空间结构出发分析参数估计系统的可靠性 ,从一个侧面扩展和丰富了测绘学中的可靠性理论 ;丰富了研究测绘学中一些基本问题的分析方法 ,也为信息学中的数据挖掘问题提供了一种分析思路     

一种新的多通道GPS共视资料的处理算法

提出了一种按仰角加权的多通道GPS共视资料处理算法，充分利用了所有观测数据，同时抑制了多径等因素影响，从而可提高共视比对精度。对日本邮政省通讯研究所(CRL)和国家授时中心(NTSC)2002年5月～2003年3月的多通道共视比对的处理结果表明，新的处理算法结果更接近真实钟差。