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Area Estimates (area + estimate)

Distribution by Scientific Domains

Earth and Environmental Science	75%

Selected Abstracts

European snow cover extent variability and associations with atmospheric forcings

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2010
Gina R. Henderson
Abstract Snow cover in Europe represents an important component of the region's climatic system. Variability in snow cover extent can have major implications on factors such as low-level atmospheric temperatures, soil temperatures, soil moisture, stream discharge, and energy allocation involved in the warming and melting of the snowpack. The majority of studies investigating Northern Hemisphere snow cover identify European snow cover extent as a portion of the Eurasian record, possibly masking complexities of this subset. This study explores the variability of European snow cover extent from 1967,2007, with the region in question including the area of Europe extending eastward to the Ural Mountains (60°E). Using the 89 × 89 gridded National Oceanic and Atmospheric Administration (NOAA) Northern Hemisphere weekly satellite snow cover product, area estimates of seasonal snow cover were calculated, and their relationship to gridded temperature, precipitation, and sea-level pressure data analysed. The spatial variability of snow cover extent was also explored using geographical information systems (GIS). The combined results from both surface temperature and precipitation analyses point towards snow cover extent in Europe being primarily temperature dependent. Atmospheric variables associated with extremes in snow cover extent were investigated. Large (small) European snow extent is associated with negative (positive) 850 hPa zonal wind anomalies, negative (positive) European 1000,500 hPa thickness anomalies, and generally positive (negative) Northern European precipitation anomalies. Sea-level pressure and 500 hPa results indicate strong associations between large (small) snow cover seasons and the negative (positive) phase of the North Atlantic Oscillation. Copyright © 2009 Royal Meteorological Society [source]

A test of two methods of radiographically deriving long bone cross-sectional properties compared to direct sectioning of the diaphysis

INTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 5 2002
Jay T. Stock
Abstract Numerous studies have made use of cross-sectional geometry to describe the distribution of cortical bone in long bone diaphyses. Several methods can be used to measure or estimate cross-sectional contours. Direct sectioning (DSM) of the diaphysis is not appropriate in most curatorial contexts, and is commonly substituted with methods based upon bi-planar radiography: a latex cast method (LCM) or an eccentric elliptical method (EEM). Previous studies have demonstrated that the EEM provides accurate estimates of area measurements, while providing less accurate estimates of second moments of area (Biknevicius & Ruff, 1992; Runestad et al., 1993; Lazenby, 1997). The LCM has been commonly employed, as a way to estimate section contours more accurately, yet the validity of this method has not been adequately documented. This study measures the agreement of these methods against DSM of long bone diaphyses using 21 sections of canine tibiae derived from a study of total hip arthroplasty. The accuracy and agreement of these methods is evaluated using reduced major axis regression, paired sample t-tests and tests for agreement (Bland & Altman, 1986). The results illustrate that the LCM provides a reasonable estimate of cross-sectional dimensions, producing cross-sectional properties that are on average within 5% of properties derived from the DSM. The EEM is found to provide adequate estimates of true cross-sectional areas, but poor estimates of second moments of area. The use of the LCM is supported for all cross-sectional properties, but the EEM is only accurate in total area, cortical area and percent cortical area estimates. Copyright © 2002 John Wiley & Sons, Ltd. [source]

A framework for progressively improving small area population estimates

JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2004
Philip Rees
Summary., The paper presents a framework for small area population estimation that enables users to select a method that is fit for the purpose. The adjustments to input data that are needed before use are outlined, with emphasis on developing consistent time series of inputs. We show how geographical harmonization of small areas, which is crucial to comparisons over time, can be achieved. For two study regions, the East of England and Yorkshire and the Humber, the differences in output and consequences of adopting different methods are illustrated. The paper concludes with a discussion of how data, on stream since 1998, might be included in future small area estimates. [source]

Quantifying sponge erosions in Western Australian pearl oyster shells

AQUACULTURE RESEARCH, Issue 9 2010
Sabine Daume
Abstract This paper describes several methods to estimate the amount of sponge erosion in pearl oyster shells (Pinctada maxima Jameson, 1901). Internal erosion can be calculated from non-destructive surface area estimates because a clear relationship was found between the eroded area on the surface of the shells and internal erosions. Grading shells into three different categories, according to the severity of erosion, also proved to be a suitable method to quickly assess the amount of sponge erosions. All methods were more accurate in shells with larger amounts of erosions. Using the described methods, the Lacepedes fishing ground was more diverse in bioeroding sponge species compared with sites at the 80-Mile fishing ground locations. Pione velans Hentschel, 1909 was the dominant bioeroding sponge species but Cliona dissimilis Ridley and Dendy, 1886 eroded more shell material than P. velans. Observed patterns suggest that P. velans had a more recent recruitment than C. dissimilis. We suggest that visual grading together with estimates from the shell surface will be sufficient to determine the general long-term trends in bioeroding sponge severity. However, results of monitoring programmes need to be supplemented by histological examination to confirm sponge activity and species identity. [source]