Combining climate model output via model correlations

In climate science, collections of climate model output, usually referred to as ensembles, are commonly used devices to study uncertainty in climate model experiments. The ensemble members may reflect variation in initial conditions, different physics implementations, or even entirely different climate models. However, there is a need to deliver a unified product based on the ensemble members that reflects the information contained in whole of the ensemble. We propose a technique for creating linear combinations of ensemble members where the weights are constructed from estimates of variation and correlation both within and between ensemble members. At the heart of this approach is a Bayesian hierarchical model that allows for estimation of the correlation between ensemble members as well as the study of the impact of uncertainty in the parameter estimates of the hierarchical model on the weights. The approach is demonstrated on an ensemble of regional climate model (RCM) output.     

A newF-layer model

Summary The model originally constructed for theF1-layer is adapted to enable an investigation of both theF-layers. Essential premises are: The ionization of a single constituent of atmosphere by monochromatic radiation. A positive temperature gradient in theFl-region, a temperature—independent from height—in theF2-region and a negative temperature gradient above the height of theF2-electron-peak; furthermore during the daytime strong heating in theF2-region. It is further assumed that the rate of electron loss in theF1-layer is proportional to the square of the density of the electrons, and in theF2-layer is in simple proportion to this density. It is also assumed that this electron loss stands in proportion to the powerk of the pressurep, and to the powern of the absolute temperatureT, as assumed in the originalF1-layer model.The above mentioned assumption as to temperature conditions are essential to an understanding of the transition from static to dynamic conditions observed in theF2-layer. During the night and in the morning theF2-layer can be treated as a static problem, movement of air-masses being of no great importance. Later in the day however an labile stratification of air-masses gives rise to such movement that theF2-layer can only be handled as a dynamic problem, particular attention being paid to the movement of the air.Numerous observational data are referred to in order to prove the practicability of the new model and, with the help of this model, to justify new assertions. It has been possible for example, to calculate the yearly temperature variation at a constant level in theF1-layer.A critical report upon the models published recently by other authors concludes this paper.

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Zusammenfassung Das seinerzeit nur für dieF1-Schicht aufgestellte Modell wird so erweitert, daß eine Deutung beiderF-Schichten möglich wird. Wesentliche Voraussetzungen sind: Ionisierung eines einzigen Bestandteiles der Luft durch eine monochromatische Strahlung. Ein positiver Temperaturgradient im Bereich derF1-Schicht, eine höhen-unabhängige Temperatur im Bereich derF2-Schicht und ein negativer Temperaturgradient oberhalb des Ionisationsmaximum, derF2-Schicht. Weiters wird vorausgesetzt, daß der Elektronenvernichtungsprozeß in derF1-Schicht dem Quadrat der Elektronendichte proportional sei, in derF2-Schicht soll er dagegen der Elektronendichte einfach proportional sein. Eine Abhängigkeit dieses Prozesses von derk-ten Potenz des Druckes,p und von dern-ten Potenz der absoluten TemperaturT wird hier vom ursprünglichenF1-Schicht-Modell übernommen.Erst die genannten Annahmen über die Temperaturverhältnisse machen den beobachteten Übergang von statischen zu dynamischen Verhältnissen in derF2-Schicht verständlich. Während der Nacht und am Morgen bis in die ersten Vormittagsstunden kann dieF2-Schicht als statisches Problem behandelt werden, die Bewegungsvorgänge der Luftmassen spielen eine nur untergeordnete Rolle. Darnach aber ruft eine labile Schichtung der Luftmassen kräftige Luftbewegungen hervor, sodaß dieF2-Schicht nur mehr als dynamisches Problem mit besonderer Berücksichtigung von Luftmassenverschiebungen behandelt werden kann.Zahlreiche Beobachtungsdaten werden herangezogen, um die Anwendbarkeit des neuen Modells zu beweisen und um mit Hilfe des Modells zu neuen Aussagen zu gelangen. Es gelingt so z. B., den Jahresgang der Temperatur in einem konstant gehaltenen Druckniveau derF1-Schicht anzugeben.Eine kritische Betrachtung der Modelle, die in letzterer Zeit von anderen Autoren veröffentlicht wurden, beschließt die Arbeit.

     

Patuxent landscape model: 1. Hydrological model development

We developed a spatially explicit, process-based model of the 2352 km² Patuxent river watershed in Maryland, and its subwatersheds to integrate data and knowledge over several spatial, temporal and complexity scales, and to serve as an aid to regional management. The model was developed using the Library of Hydro-Ecological Modules (LHEM, http://giee.uvm.edu/LHEM), which was designed to create flexible landscape model structures that can be easily modified and extended to suit the requirements of a variety of goals and case studies. The LHEM includes modules that simulate various aspects of ecosystem dynamics. In this paper we consider modules that represent the physical conditions in the environment (climatic factors, geoporphology), and hydrologic processes, both locally and spatially. Where possible the modules are formulated as Stella(R) models, spatial transport processes are presented as C++ code.     

Developing land use scenario dynamics model by the integration of system dynamics model and cellular automata model

Models of land use change are useful tools for un-derstanding the analysis of the cause and conse-quences of land use changes, assessing the impacts of land use system on ecological system and supporting land use planning and policy[1,2]. Modeling land use scenario changes and its potential impacts on the structure and function of the ecosystem in the typical regions are regarded as one of the good ways to un-derstand the interactive mechanism between land use system and ecological system[3―10…     

泛协克里金的对偶形式

针对最一般的泛协克里金,借助矩阵分析方法表述出了它的对偶形式,并用空间自伴算子和空间共轭空间的观点给对偶克里金的实质作出了解释．借助对偶克金的结果,把泛协克里金的估计结果表成线性插值形式,从而请楚地显示出泛协克里格估计的插值和外推性质．     

Numerical model for quantitative precipitation forecasting

Summary A numerical model for the quantitative precipitation forecasting has been formulated. In this model precipitation is computed as a function of the vertical velocity and humidity distribution in the atmosphere. The orographic influence on the vertical velocity was taken into consideration. Further, the relation between vertical velocity and static stability of the atmosphere has been considered and, as an important factor in the condensation process, was introduced into the equation of the model. This numerical model for the precipitation forecasting has been applied in the North Adriactic Sea region, which is characterized by a strong vertical gradient of the specific humidity and pronounced orographic influence. The results achieved show that this model could successfully be used as an objective method in the routine forecasting of the amount of precipitation.     

A deformation/blurring-based spatio-temporal model

A key objective in spatio-temporal modeling consists of providing an appropriate representation of complexity in interactive spatio-temporal dynamics inherent to real phenomena. Propagated effect of dynamical spatial deformation provides a meaningful way to describe certain forms of heterogeneous behaviour; in particular, in relation to processes evolving in unstable media, or to account for the possible effect of covariates, to mention some significant interpretations. In this paper, the formulation of a discrete time and continuous space spatio-temporal interaction model with autoregressive dynamics, incorporating the effect of continuous deformation of the spatial support over time, is studied. Among other fields, this approach provides a suitable representation for a variety of geophysical and environmental applications. In particular, a vast family of heterogeneous models is generated from models which display homogeneity in the absence of deformation. Structural characteristics and variability properties, as well as self-consistency conditions for a limiting continuous-time approximation, are analyzed.     

Multicriteria sensitivity analysis as a diagnostic tool for understanding model behaviour and characterizing model uncertainty

Complex hydrological models are being increasingly used nowadays for many purposes such as studying the impact of climate and land‐use change on water resources. However, building a high‐fidelity model, particularly at large scales, remains a challenging task, due to complexities in model functioning and behaviour and uncertainties in model structure, parameterization, and data. Global sensitivity analysis (GSA), which characterizes how the variation in the model response is attributed to variations in its input factors (e.g., parameters and forcing data), provides an opportunity to enhance the development and application of these complex models. In this paper, we advocate using GSA as an integral part of the modelling process by discussing its capabilities as a tool for diagnosing model structure and detecting potential defects, identifying influential factors, characterizing uncertainty, and selecting calibration parameters. Accordingly, we conduct a comprehensive GSA of a complex land surface–hydrology model, Modélisation Environmentale–Surface et Hydrologie (MESH), which combines the Canadian land surface scheme with a hydrological routing component, WATROUTE. Various GSA experiments are carried out using a new technique, called Variogram Analysis of Response Surfaces, for alternative hydroclimatic conditions in Canada using multiple criteria, various model configurations, and a full set of model parameters. Results from this study reveal that, in addition to different hydroclimatic conditions and SA criteria, model configurations can also have a major impact on the assessment of sensitivity. GSA can identify aspects of the model internal functioning that are counter‐intuitive and thus help the modeller to diagnose possible model deficiencies and make recommendations for improving development and application of the model. As a specific outcome of this work, a list of the most influential parameters for the MESH model is developed. This list, along with some specific recommendations, is expected to assist the wide community of MESH and Canadian land surface scheme users, to enhance their modelling applications.     

A bivariate pareto model for drought

Univariate Pareto distributions have been so widely used in hydrology. It seems however that bivariate or multivariate Pareto distributions have not yet found applications in hydrology, especially with respect to drought. In this note, a drought application is described by assuming a bivariate Pareto model for the joint distribution drought durations and drought severity in the State of Nebraska. Based on this model, exact distributions are derived for the inter arrival time, magnitude and the proportion of droughts. Estimates of 2, 5, 10, 20, 50 and 100 year return periods are derived for the three variables, drought duration, drought severity and the pairwise combinations: (drought duration, drought severity), (inter arrival time of drought, proportion of drought) and (drought duration, drought magnitude). These return period estimates could have an important role in hydrology, for example, with respect to measures of vegetation water stress for plants in water-controlled ecosystems.     

顾及次优噪声模型的GNSS坐标时间序列噪声模型选择

在全球导航卫星系统（Global Navigation Satellite System,GNSS）坐标时间序列噪声建模领域,选择合适的噪声模型对GNSS坐标时间序列的速度信号提取具有重要价值.长期以来,研究者专注于建立最优噪声模型来描述GNSS坐标时间序列中的噪声成分,却往往直接忽略与最优噪声模型性能接近的次优噪声模型.本文选用8种常见的噪声模型,使用极大似然估计法（Maximum Likelihood Estimate,MLE）估计模型参数,以赤池信息量准则（Akaike information criterion,AIC）作为评价准则来选取噪声模型.实验数据采用中国区域12个国际GNSS服务（International GNSS Service,IGS）基准站36个坐标分量及全球范围内50个IGS基准站150个坐标分量的坐标时间序列.结果表明,超过半数的测站坐标分量上存在与最优噪声模型性能接近的次优噪声模型.在此基础上中国区域的IGS站,在东方向有14%的次优噪声模型拥有比最优噪声模型数值更大的速度不确定度,在北方向和垂直方向,这一值分别为33%和63%.而对于全球范围的IGS站,这一值分别为31%、39%和48%.因此在GNSS坐标时间序列噪声模型选择过程中,充分考虑与最优噪声模型性能接近的次优噪声模型有助于获得到更保守的估计结果.

     

新型随机地震动模型

在研究结构的随机地震反应时，要用大量的符合场地条件的地震记录作为输入数据。但强震历史记录却不是每个地区都有的，因此根据符合场地条件的现有地震记录建立随机地震动模型具有重要意义。本文利用中国抗震规范2001版修正选取的样本波作为目标波，考虑了幅值和频率的双重非平稳性，建立了新型随机地震动模型——改进的时变ARMA模型随机地震动模型。通过使用残差的卡方检验法，对多种非平稳ARMA模型生成的模拟波进行检验；同时又比较丁模拟波与目标波的功率谱密度图和反应谱图。结果证明：此法能够更精确地反映不同场地条件地震动的频谱和幅值的真实内容，从而建立符合目标场地条件的更为有效的模拟地震动，为相关研究与工程设计架起一座桥梁。     

A SANISAND model with anisotropic elasticity

Numerous experimental studies indicate that as a result of shear stress, the elastic behavior of granular media becomes both non-linear and anisotropic. This paper presents a simple constitutive model for sands with respect to anisotropic elasticity. To this aim, using the concept of second order fabric tensor, a simplified elasticity theory is presented which is capable of considering the effect of induced anisotropy on the elastic response. SANISAND is the name used for a family of simple anisotropic sand models developed in the framework of critical state soil mechanics and bounding surface plasticity. An existing SANISAND model is modified in order to include the proposed anisotropic elasticity. The modified model simulations are compared with those obtained from the other members of this family. It is shown that considering anisotropic elasticity can take part in explanation of drastic loss of mean principal stress when sand is subjected to reverse loading in dilative branch of behavior and as a result, improve the liquefaction simulations.     

A branching model for crack propagation

Summary A branching model for crack propagation is proposed, a branch corresponding to an existing microfissure or flaw in the material, and the propagation of the crack to the coalescence of such branches. Increase in external stress increases the probability that a given branch will link into more than a specified number of further branches. Such increases can continue until a critical state is reached when the mean number of branches linking into a given branch is equal to unity; beyond this point, the system becomes unstable, and any slight movement is likely to lead to catastrophic rupture. The distribution of the sums of the lengths of the branches linked together in a cracking episode is investigated, and shown to lead, in the critical case, to a Gutenberg-Richter type relation with parameterb=0.75. Departures from this value are attributed to the influence of the distribution of the lengths of preexisting fissures, this distribution varying with the strength of the material and its stress history. Some difficulties with the theoretical model of Scholz are raised, and it is suggested that a more complete analysis of Scholz's model should lead to results qualitatively similar to those obtained for the branching model.     

A generalized two-disk dynamo model

Abstract

A generalized two-disk dynamo model is considered that includes mechanical friction; this model is intended to simulate in its broad character the behavior of the geodynamo. Fixed points, limit cycles and chaotic attractors are located for different input parameters of the model. The chaotic regimes are of several kinds as are the “routes to chaos”. Several approximate models, helpful for studying the dynamo are discussed. A number of essential differences from the well-known Rikitake dynamo are demonstrated.     

JD-2F型井下地震计

JD-2F型井下地震计是在JD-2型深井地震仪的基础上，经过进一步的技术改进并引入电子反馈技术而研制成功的。它是为井下地震台的数字化改造而研制的，是JD-2型地震仪的替代产品。本文通过对比，重点介绍了它的主要技术指标及结构特点。     

Cluster computing-aided model updating for a high-fidelity finite element model of a long-span cable-stayed bridge

Accurate and high-fidelity finite element (FE) models are in great demand in the design, performance assessment, and life-cycle maintenance of long-span cable-stayed bridges. The structural system of a long-span cable-stayed bridge is often huge in size and complex with many components connected and various materials constituted. Therefore, the FE model of a long-span cable-stayed bridge involves a large number of elements and nodes with many uncertainties. The model updating of the FE model to best represent a real bridge is necessary but very challenging. One of the challenging issues is that the numerical computation needed for searching the global optimum of a large set of structural parameters is so extensive that the existing FE (not surrogate) model-based updating methods cannot fulfill this task. In this study, a cluster computing-aided FE model updating framework is proposed for the high-performance FE model updating of large and complex structures. In the framework, several computer software packages, including MSC.Marc, Python, and MATLAB, are interconnected for making use of their respective functions of strength. The shake table test of a scaled physical structure of the Sutong cable-stayed bridge in China is used to validate the accuracy and efficiency of the proposed framework. The simulated bridge responses based on the updated FE model are in good agreement with the measured ones from the shake table test. The successful application of the proposed framework provides a reference for the model updating of other types of large and complex structures.     

An analytical model for ice-edge upwelling

Abstract

This paper presents an analytical, two-dimensional model of the wind-induced homogeneous circulation near the edge of an ice pack floating on the ocean surface. It is shown that a vertical shear layer arises under the ice edge, by which the wind-driven geostrophic motion in the open ocean is matched to the flow region underneath the ice. As in coastal upwelling models, this shear layer consists of a thin E ^1/2-layer inside a thicker E ^1/4-layer (E being the Ekman number). Under certain conditions the shear layer produces a vertical mass flux from the bottom to the surface Ekman layer. Near the surface this upwelling flux is concentrated in the narrow E ^1/2-layer. Comparison with observations of upwelling at the edge of a polar ice pack shows good agreement.     

An attenuation model for distant earthquakes

Large magnitude earthquakes generated at source–site distances exceeding 100km are typified by low‐frequency (long‐period) seismic waves. Such induced ground shaking can be disproportionately destructive due to its high displacement, and possibly high velocity, shaking characteristics. Distant earthquakes represent a potentially significant safety hazard in certain low and moderate seismic regions where seismic activity is governed by major distant sources as opposed to nearby (regional) background sources. Examples are parts of the Indian sub‐continent, Eastern China and Indo‐China. The majority of ground motion attenuation relationships currently available for applications in active seismic regions may not be suitable for handling long‐distance attenuation, since the significance of distant earthquakes is mainly confined to certain low to moderate seismicity regions. Thus, the effects of distant earthquakes are often not accurately represented by conventional empirical models which were typically developed from curve‐fitting earthquake strong‐motion data from active seismic regions. Numerous well‐known existing attenuation relationships are evaluated in this paper, to highlight their limitations in long‐distance applications. In contrast, basic seismological parameters such as the Quality factor (Q‐factor) could provide a far more accurate representation for the distant attenuation behaviour of a region, but such information is seldom used by engineers in any direct manner. The aim of this paper is to develop a set of relationships that provide a convenient link between the seismological Q‐factor (amongst other factors) and response spectrum attenuation. The use of Q as an input parameter to the proposed model enables valuable local seismological information to be incorporated directly into response spectrum predictions. The application of this new modelling approach is demonstrated by examples based on the Chi‐Chi earthquake (Taiwan and South China), Gujarat earthquake (Northwest India), Nisqually earthquake (region surrounding Seattle) and Sumatran‐fault earthquake (recorded in Singapore). Field recordings have been obtained from these events for comparison with the proposed model. The accuracy of the stochastic simulations and the regression analysis have been confirmed by comparisons between the model calculations and the actual field observations. It is emphasized that obtaining representative estimates for Q for input into the model is equally important.Thus, this paper forms part of the long‐term objective of the authors to develop more effective communications across the engineering and seismological disciplines. Copyright © 2003 John Wiley & Sons, Ltd.     

基于多植物生长模式的SWAT模型的修正与有效性初探

以农林系统的非点源污染模拟为目标,通过研究建立变化密度及多种类混杂的森林生长模型,修正了SWAT模型采用平均森林植被密度和单一植物生长模式估算生物累积量的问题,并建立了与之相适应的森林优势组份丰度遥感反演模型、叶面积指数和消光系数遥感反演模型以获取森林生长模型的相关参数.同时,根据间作套种下的辐射能利用Keating方程,引入间作套种指数变量,修正SWAT原有的单一生物量日积累模型,探讨了作物复种指数、间作套种指数遥感反演方法和以此为基础的作物间作套种生长模型.以亚热带季风湿润区红壤背景下的鄱阳湖流域子流域梅江流域为试验区,以野外实测数据为基础,探讨修正SWAT模型的有效性.结果表明:修正后的SWAT模型与原始SWAT模型相比,在模拟流量和营养盐负荷方面,得到了较好的改善.在模拟流量方面,有效性提高了7.8%,流量峰值的模拟也得到了改善,能更好地反映地表蓄流方面的实际情况;在模拟营养盐负荷方面,有效性提高了6.4%(总磷)和6.1%(总氮).