基于回归克里格的生态水文无线传感器网络布局优化   总被引：2，自引：1，他引：1  

葛咏  王江浩  王劲峰  晋锐  胡茂桂 《地球科学进展》2012,27(9):1006-1013

在黑河上游八宝河流域建立自动化、时空协同、智能观测的生态水文无线传感器网络,实现分布式的地面观测,对于定量刻画流域尺度时空异质性较强的生态水文要素的动态特征及其不确定性具有重要意义。在观测网设计过程中,节点的空间布局将直接影响到无线传感器网络的观测水平。为准确捕捉流域内关键生态水文要素的时空变异性和场分布,探讨了一种基于回归克里格模型的空间采样布局优化方法,并以地表温度观测网优化为例,应用到八宝河流域生态水文无线传感器网络布局方案设计中。研究结果表明,该优化方法同时考虑了目标变量与环境变量之间的相关关系以及残差在空间上的自相关特征,可以同时优化目标变量的地理空间和属性空间。优化后的无线传感器网络可以较好地捕捉流域内生态水文要素的时空动态特征。  相似文献   

Monitoring 25 years of land cover change dynamics in Africa: A sample based remote sensing approach   总被引：3，自引：1，他引：2  

Andreas Bernhard Brink  Hugh Douglas Eva   《Applied geography (Sevenoaks, England)》2009,29(4):501-512

The study examines the changes in sub-Saharan's natural land cover resources for a 25 year period. We assess these changes in four broad land cover classes – forests, natural non-forest vegetation, agriculture and barren – by using high spatial resolution Earth observing satellites. Two sets of sample images, one ‘historical’ targeted at 1975 and a second ‘recent’ targeted at the year 2000, have been selected through a stratified random sampling technique over the study area, targeting a sampling rate of 1% in each of the strata. The results, presented at eco-region level and aggregated at sub-Saharan level, show a 57% increase in agriculture area at the expense of natural vegetation which has itself decreased by 21% over the period, with nearly 5 million hectares forest and non-forest natural vegetation lost per year. The impacts of these changes on the environment on one site and on the socio-economy on the other site are discussed and possible pressures on human well being are highlighted.  相似文献   

On the effect of the sampling frequency of sea level measurements on return period estimate of extremes—Southern European examples     

M.N. Tsimplis  M. Marcos  B. Prez  P. Challenor  M.J. Garcia-Fernandez  F. Raicich 《Continental Shelf Research》2009,29(18):2214-2221

Estimates of extreme sea levels and return periods have been based mainly on hourly sampling rates. Technological development has enabled the sampling rates to increase and sampling rates of 5–10 min are becoming increasingly common. In this paper we explore the relationship between extreme sea levels and estimated return periods based on hourly and shorter sampling periods in three tide-gauges one at the Atlantic coasts of Spain (Coruña), one in the western Mediterranean (Malaga) and one in the N. Adriatic (Trieste). Significant differences of several centimetres are found in the hourly and 5 min extremes. These reflect in significant underestimation of the 50-year return levels which in Trieste reach 38 cm. A theoretical relationship between the high and the low sampling rate of extremes is also tested. Thus updated 50-year return levels for the Mediterranean and the coasts of the Iberian peninsula are produced assuming that the differences identified in the various stations generalise to other tide-gauge (hourly) records for which hourly values have been analysed earlier.  相似文献   

Evaluating the utility of the ensemble transform Kalman filter for adaptive sampling when updating a hydrodynamic model   总被引：1，自引：0，他引：1  

Jeffrey C. Neal  Peter M. Atkinson  Craig W. Hutton 《Journal of Hydrology》2009,375(3-4):589-600

This paper compares two Monte Carlo sequential data assimilation methods based on the Kalman filter, for estimating the effect of measurements on simulations of state error variance made by a one-dimensional hydrodynamic model. The first method used an ensemble Kalman filter (EnKF) to update state estimates, which were then used as initial conditions for further simulations. The second method used an ensemble transform Kalman filter (ETKF) to quickly estimate the effect of measurement error covariance on forecast error covariance without the need to re-run the simulation model. The ETKF gave an unbiased estimate of EnKF analysed error variance, although differences in the treatment of measurement errors meant the results were not identical. Estimates of forecast error variance could also be made, but their accuracy deteriorated as the time from measurements increased due in part to model non-linearity and the decreasing signal variance. The motivation behind the study was to assess the ability of the ETKF to target possible measurements, as part of an adaptive sampling framework, before they are assimilated by an EnKF-based forecasting model on the River Crouch, Essex, UK. The ETKF was found to be a useful tool for quickly estimating the error covariance expected after assimilating measurements into the hydrodynamic model. It, thus, provided a means of quantifying the ‘usefulness’ (in terms of error variance) of possible sampling schemes.  相似文献   

汶川8.0级地震周至深井水震波的记录特征     

舒优良  张世民  黄辅琼 《震灾防御技术》2014,9(S1):572-580

介绍了周至深井概况和水位高速采样技术系统的仪器设备配置。通过对该井2008年5月12日汶川8.0级大震及强余震的50Hz采样率水震波数字化记录进行分析,与同一台站的测震和强震动记录开展对比研究。结果表明,周至深井动水位对全球中强地震具有良好的观测效果,相当于一台深井宽带地震仪。  相似文献   

A theoretical method for determining sample mass in a sieving test     

《Computers and Geotechnics》2017

Obtaining a representative particle size distribution for soil is a common challenge in earth works and is affected by the size of sieving samples. While the current standards usually specify a minimum sample mass, there is no scientific justification for the specification. Treating the preparation of sieving samples as a process of random sampling, a new method is proposed for determining the minimum mass of a sieving test sample. The proposed method is validated via laboratory tests and will improve standard specification and engineering practice.  相似文献   

Sub-kilometer length scales in coastal waters     

Shelley M. Blackwell  Mark A. Moline  Andrew Schaffner  Thomas Garrison  Grace Chang 《Continental Shelf Research》2008

Patchiness or spatial variability is ubiquitous in marine systems. With increasing anthropogenic impacts to coastal resources and coastal systems being disproportionately large contributors to ocean productivity, identifying the spatial scales of this patchiness, particularly in coastal waters, is of critical importance to understand coastal ecosystem dynamics. The current work focuses on fine scale structure in three coastal regions. More specifically, we utilize variogram analyses to identify sub-kilometer scales of variability in biological and physical parameters measured by an autonomous underwater vehicle (AUV) in the Mid-Atlantic Bight, Monterey Bay, and in San Luis Obispo Bay between 2001 and 2004. Critical scales of variability in density, turbidity, fluorescence, and bioluminescence are examined as a function of depth and distance offshore. Furthermore, the effects of undersampling are assessed using predictive error analysis. Results indicate the presence of scales of variability ranging from 10s to 100s of meters and provide valuable insight for sampling design and resource allocation for future studies.  相似文献   

Abflußereignisse,eine skalenabhängige multiple Antwort von Einzugsgebieten auf Niederschläge     

W. Symader  R. Bierl  F. Gasparini 《洁净——土壤、空气、水》1999,27(2):87-93

Flood Events, a Multiple Basin Response to Precipitation Events at Different Scales Results in the small catchment of the Kartelbornsbach have shown that summer events lead to typical types of flood waves that can be classified according to their response patterns. Differences to this pattern are due to the precipitation amount and duration and in some times to the pre-event moisture of the soil. The results show further that the Kartelbornsbach catchment can be considered as a block system where spatial differences are responsible for the basic pattern of the reaction but not for differences between flood events. Small catchments are excellent tools for relatively inexpensive hydrological and hydrochemical research on streamflow generation mechanisms. With increasing size of the basin the response becomes less clear, because the spatial distribution of rainfall and the distance of delivering areas from the sampling station mask or modify the type of response. Although the main flow components may not change, there is a considerable shift in the composition of water quality, because the increase of travel time does not affect all flow components at the same rate.  相似文献   

一种准中断直接输入的实用高速采集系统     

姚振东  王贤勤  王树才  佘勇 《成都信息工程学院学报》1990,(4)

高速采集系统不仅要有高速A/D,而且必须有高速的采集方式。本文提出一种简单易行的高速采集接口电路,并对关键性技术进行分析,最后给出软件流程图和结果。  相似文献   

电场仪数据采集自记和实时显示记录系统   总被引：1，自引：1，他引：0  

陈成品  肖正华 《高原气象》1998,17(3):328-334

叙述了用单片机以大气电场仪测量值的Ａ／Ｄ转换和存贮,介绍了其硬件原理和两种工作方式以及软件编程,该系统提供了地面电场仪记录存贮的一种较为灵活方便的新方法。  相似文献