Scaling characteristics of spatial patterns of soil moisture from distributed modelling

Characterizing the spatial dynamics of soil moisture fields is a key issue in hydrology, offering an avenue to improve our understanding of complex land surface–atmosphere interactions. In this paper, the statistical structure of soil moisture patterns is examined using modelled soil moisture obtained from the North American Land Data Assimilation System (NLDAS) at 0.125° resolution. The study focuses on the vertically averaged soil moisture in the top 10 cm and 100 cm layers. The two variables display a weak dependence for lower values of surface soil moisture, with the strength of the relationship increasing with the water content of the top layer. In both cases, the variance of the soil moisture follows a power law decay as a function of the averaging area. The superficial layer shows a lower degree of spatial organization and higher temporal variability, which is reflected in rapid changes in time of the slope of the scaling functions of the soil moisture variance. Conversely, the soil moisture in the top 100 cm has lower variability in time and larger spatial correlation. The scaling of these patterns was found to be controlled by the changes in the soil water content. Results have implications for the downscaling of soil moisture to prevent model bias.     

信息化时代的地图学

首先简要论述了信息化时代地图学作为科学与技术的含义和任务 ,然后从地图学着重点的转移、地图学功能的扩展与延伸、地图学的新的生长点和地图制图生产的自动化等四个方面 ,分析了信息化时代地图学的特征。     

县级土地利用动态更新方法研究

采用“3S”的空间信息技术进行土地资源动态监测与快速更新是一先进的方法和手段。本文从遥感和全球定位系统融合实现土地动态更新着手 ,提出基于“3S”技术的县级土地利用动态更新系统的开发模式 ,及其系统实现方法.     

Accounting for spatial patterns of multiple geological data sets in geological thematic mapping using GIS-based spatial analysis

This paper presents a Geographic Information System (GIS)-based spatial analysis scheme to account for spatial patterns and association in geological thematic mapping with multiple geological data sets. The multi-buffer zone analysis, the main part of the present study, was addressed to reveal the spatial pattern around geological source primitives and statistical analysis based on a contingency table was performed to extract information for the assessment of an integrated layer. Mineral potential mapping using multiple geological data sets from Ogdong in Korea was carried out to illustrate application of this methodology. The results obtained from the case study indicated that some geochemical elements and residual magnetic anomaly dominantly affected spatial patterns of the mineral potential map in the study area and the dominant classes of input data layers were also extracted. This information on spatial patterns of multiple geological data sets around mines could be used as effective evidences for the interpretation of the integrated layer within GIS.     

Experimental study of the transfer velocity for urban surfaces with a water evaporation method

A major problem in urban climate modelling is determining how the heat fluxes from various canyon surfaces are affected by canyon flow. To address this problem, we developed a water evaporation method involving filter paper to study the distribution of the convective transfer velocity in urban street canyons. In this method, filter paper is pasted onto a building model and the evaporation rate from the paper is measured with an electric balance. The method was tested on 2D (two-dimensional) street canyon models and 3D model arrangements. Moreover, in this technique, it is easy to restrict the flux within an arbitrary surface in question. That is, the evaporation distribution on a surface can be studied by using several small pieces of filter paper. In the 2D case, the wall transfer velocity was strongly dependent on the canyon aspect ratio for perpendicular wind directions and it varied widely with height within both windward and leeward wall surfaces. For 3D cubic arrays, the relation to canyon aspect ratio was largely different from that of the 2D canyon. And, as a case study, the variation of wind direction was investigated for a city-like setting. The area-averaged transfer velocity was insensitive to wind direction but its local deviation was significant. Finally, we measured the transfer velocity for a clustered block array surrounded by relatively wide streets. The effect of spatial heterogeneity on the transfer velocity was significant. Moreover, for a fixed total building volume, the transfer velocity was considerably larger when the building height varied than when it was uniform. Therefore, the water evaporation method with filter paper is expected to be useful for studying the transfer velocity and ventilation rates in urban areas with various canyon shapes.     

Enhancing a GIS Cellular Automata Model of Land Use Change: Bayesian Networks, Influence Diagrams and Causality

Cellular Automata (CA) models at present do not adequately take into account the relationship and interactions between variables. However, land use change is influenced by multiple variables and their relationships. The objective of this study is to develop a novel CA model within a geographic information system (GIS) that consists of Bayesian Network (BN) and Influence Diagram (ID) sub‐models. Further, the proposed model is intended to simplify the definition of parameter values, transition rules and model structure. Multiple GIS layers provide inputs and the CA defines the transition rules by running the two sub‐models. In the BN sub‐model, land use drivers are encoded with conditional probabilities extracted from historical data to represent inter‐dependencies between the drivers. Using the ID sub‐model, the decision of changing from one land use state to another is made based on utility theory. The model was applied to simulate future land use changes in the Greater Vancouver Regional District (GVRD), Canada from 2001 to 2031. The results indicate that the model is able to detect spatio‐temporal drivers and generate various scenarios of land use change making it a useful tool for exploring complex planning scenarios.     

城市地下综合管网信息系统的设计与实现关键技术

城市地下综合管网是城市的生命线,是城市规划建设管理的重要基础信息。本文在研究城市地下综合管网关键技术的基础上,重点论述了城市地下综合管网信息系统的总体结构设计、主要功能模块设计等内容。     

基于ArcSDE的信息基础设施空间数据库的设计与实现

ArcSDE作为空间数据引擎,在地理信息系统中有着广泛的应用,它能有效的提高空间数据库的管理效率。本文在对常用空间数据引擎比较的基础上,根据信息基础设施空间数据种类多、数据量大的特点,提出了基于ArcSDE SQL Server 2000技术构建的信息基础设施空间数据库建设方案,实现了海量数据的空间存储和有效管理,有利于信息的共享和充分利用,并在实际应用中取得了很好的效果。     

基于ArcSDE的信息基础设施空间数据库的设计与实现

ArcSDE作为空间数据引擎，在地理信息系统中有着广泛的应用，它能有效的提高空间数据库的管理效率。本文在对常用空间数据引擎比较的基础上，根据信息基础设施空间数据种类多、数据量大的特点，提出了基于ArcSDE＋SQLServer2000技术构建的信息基础设施空间数据库建设方案，实现了海量数据的空间存储和有效管理，有利于信息的共享和充分利用，并在实际应用中取得了很好的效果。     

福建省基础空间数据管理技术研究

福建省基础地理信息中心作为福建省基础空间数据的管理和分发服务单位，管理和分发福建省多种类、多比例尺、多数据源、分布式、多时态的基础空间信息，在基础空间数据管理上存在多种形式。本文通过几种管理模式的技术分析，结合中心的管理实际，总结了福建省空间数据管理的多样性和技术特点，对比分析出各种管理模式的优势和缺点。