摘要:

AbstractThis paper considers the mean squared error (MSE) incurred in estimating an idealized earth's global average temperature with a finite number of point gauges located in a specified or stochastic way over the globe. For a class of model earths with rotationally invariant statistics, the MSE formula can be cast into the form of a summation over spherical harmonic indices. The summand factors into a part which depends on the design of the gauge network and a second part which is the degree variance spectrum of the surface temperature field. After presenting this formalism, we provide an example spectrum for the surface temperature field derived from a simple two parameter stochastic climate model defined on the sphere. An example calculation is given for the case ofNgauges randomly arranged on the sphere. In addition, the sampling error is computed for some simple regular arrays of gauges as illustrative examples.

ISSN:1180-4009    

DOI:10.1002/env.3170030101

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper considers the minimum mean squared error (MSE) incurred in estimating an idealized earth's global average temperature with a finite network of point gauges located over the globe. We use a spectral MSE formalism to find the optimal locations forNgauges in the problem of estimating the earth's global average temperature. Limiting MSE configurations are obtained as the limiting least error case for randomly distributed samples of sizeN. Our results suggest that forNgreater than about 60, one can obtain estimates such that the amount of measured variance due to sampling error is less than 10%, a result likely to be acceptable to climatologists.

ISSN:1180-4009    

DOI:10.1002/env.3170030102

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractIn this paper a statistical model of raindrop size distributions is used to examine the temporal variability of rainfall power and to develop techniques for estimating rainfall power from observations of rainfall rate and radar reflectivity factor. The model of raindrop size distributions is based on the assumptions that: 1) raindrop arrival rate at the ground can be represented by a Poisson process with randomly varying rate of occurrence and 2) diameters of raindrops have a lognormal distribution with parameters that are time‐varying random processes. The lognormal distribution plays a central role in both characterization of the temporal variability of rainfall power and in state estimation of rainfall power from rainfall rate and radar reflectivity observations. Empirical results are presented using drop‐size data from a number of sites in the United States. Spatial variability of rainfall power is examined empirically using the rainfall power‐reflectivity relationships developed from drop‐size data and radar data from the southern plains region of the United

ISSN:1180-4009    

DOI:10.1002/env.3170030103

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractA simple model was devised to estimate the number and sizes of crevices visible at the surface of submerged, artificial rock reefs intended to provide shelter for lobsters and crayfish. The model assumes that the rocks are spherical and that each crevice is formed by the independent packing of three rocks. We use this model to derive the mean and variance of the rock size distribution needed to produce a given mean and variance for a crevice size distribution. These results are used as the initial estimates in an algorithm to choose the rock size distribution which comes closest to producing a crevice size distribution appropriate for the creation of new lobster or crayfish habitat.

ISSN:1180-4009    

DOI:10.1002/env.3170030104

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractGeostatistical techniques applied to site characterization require modelling of the spatial dependence between attribute values at different locations throughout the site. The availability of this model allows for quantification of the uncertainties associated with site characterization from the sampling stages, through data analysis, and up to the three‐dimensional spatial model of the contaminant occurrence.Uncertainty models are built at each location of the grid thus providing probabilities of occurrence, probabilities of exceeding certain threshold(s) (critical value(s)), or probabilities of the true contamination value being within a specified range. Geostatistical modelling of uncertainty depends on the quality and quantity of the information available, and thus it is a useful tool for QA/QC programs as well, since a quantification of the performance of the sampling and other characterization work is readily available. If the desired level of uncertainty is not reached, the information gathering process can be modified and refined to meet the required standards.This paper outlines the assumptions behind the methodology, and provides a basic example on sampling optimization and on uncertainty analysis of the sit

ISSN:1180-4009    

DOI:10.1002/env.3170030105

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractAge composition and average annual growth rates were determined for a geoduck clam (Panope abrupta) population located in Ladysmith Harbour, British Columbia. Acetate peels were made from cross‐sections of the right shell portion of each clam. The number and distances between the annuli in shell cross‐sections were used to determine age and growth. Analysis of the growth measurements suggested the annual growth of individuals within this population in any year t was approximately 80% of the annual growth in yeart− 1. This estimate does not appear to be a function of age. An average annual index of standardized geoduck growth was constructed for the period 1907–1980. Abrupt changes in mean annual growth were detected near 1919 and 1962. Intervention analysis was employed to quantify changes in mean standardized growth at these two points in time. An 8% increase in geoduck mean annual growth was coincident with an increase in mean annual temperature around 1920. A 27% decrease in growth occurred soon after the initiation of log booming and storage in Ladysmith Harbour (about 1960). The results of this study suggest measurements of growth from geoduck shells may be useful in identifying and quantifying changes in the marine envi

ISSN:1180-4009    

DOI:10.1002/env.3170030106

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY

摘要:

AbstractTime series analysis models are very useful in modelling dynamic systems in science and engineering applications. This class of models is in fact able to represent the dynamic features of physical systems that are subject to often uncontrollable inputs with random components. Wastewater treatment plants are examples of dynamic systems, with inputs (flow, organic loads, etc.) that vary stochastically within more or less wide ranges. The use of stochastic models allows a more detailed representation of the dynamic nature of these systems, while retaining the degree of information contained in most deterministic models.In this paper, time series analysis applications to wastewater treatment plant modelling are presented and discussed. Both univariate and multivariate stochastic processes are applied to sewage treatment plant data, and the results thus obtained are further analyzed and compared with those from “conventional” deterministic models.Specifically, the above mentioned models are analyzed with respect to possible application in the daily operation of sewage treatment plants, by virtue of their predictive capacities and relative ease of determination. Furthermore, these models present other attractive features, such as adaptiveness and the possibility of extracting useful information about the system from the analysis of their structure. Adaptiveness refers to the possibility of continuously improving the model's performance as new information about the system is collected by manual or automatic monitoring. Performance of the models herein identified, and possible applications of these models in real systems are discus

ISSN:1180-4009    

DOI:10.1002/env.3170030107

出版商:John Wiley&Sons, Ltd.    

年代:1992

数据来源: WILEY