The Reliability of Global and Hemispheric Surface Temperature Records

The purpose of this review article is to discuss the development and associated estimation of uncertainties in the global and hemispheric surface temperature records. The review begins by detailing the groups that produce surface temperature datasets. After discussing the reasons for similarities and differences between the various products, the main issues that must be addressed when deriving accurate estimates, particularly for hemispheric and global averages, are then considered. These issues are discussed in the order of their importance for temperature records at these spatial scales: biases in SST data, particularly before the 1940s; the exposure of land-based thermometers before the development of louvred screens in the late 19th century; and urbanization effects in some regions in recent decades. The homogeneity of land-based records is also discussed; however, at these large scales it is relatively unimportant. The article concludes by illustrating hemispheric and global temperature records from the four groups that produce series in near-real time

Ultrasonic Analysis of Damage Development in Polymer Composites by Signal Processing Techniques

The material studied in this paper is a thermoplastic matrix (polypropylene) with short glass fiber reinforcement (SFRP). Complex geometry parts are cheaply produced in a process called injection molding, thus it is commonly used in numerous applications. Abe et al. [1] characterized the flow pattern of fiber reinforced polypropylene with ultrasonic C- Scans. Matsushige et al. [2] applied single pulse spectroscopy to polymeric materials. They studied the effect of glass fiber diameter and content on the ultrasonic frequency spectrum and interpreted their results according to the different scattering regimes (πD/λ ≪ 1, πD/λ, ≈ 1, πD/λ ≫ 1; D: size of the scatterer, λ: wavelength). Newell et al. [3] determined elastic constants of an approximately orthotropic cellulose fiber reinforced polypropylene by velocity measurements in the 0.5 to 5 MHz range. They observed that the dispersion curves level off at frequencies above 1 MHz, which is consistent with a relaxation time constant of the order of a few microseconds. Chu and Rokhlin [4] used longitudinal and transverse velocity measurements to characterize the fiber/matrix interphase in ceramic composites.</p

SPECCHIO: a spectrum database for remote sensing applications.

Representative and comprehensive information on the spectral properties of natural and artificial materials on the Earth's surface is highly relevant in aircraft or satellite remote sensing, such as geological mapping, vegetation analysis, or water quality estimation. For this reason, the spectrum database SPECCHIO (Spectral Input/Output) has been developed, offering ready access to spectral campaign data, modelled data, and existing spectral libraries. Web-based and command line interfaces allow for the input of spectral data of heterogeneous formats and descriptions, as well as interactive queries, previews, and downloads. ASCII and ENVI spectral library data formats are currently supported. SPECCHIO is used as a reference database for the retrieval of geophysical and biophysical parameters from remotely sensed data, accounting for the frequent lack of surface spectra. The database is also used for the general management of spectral data, including detailed ancillary data. (C) 2002 Elsevier Science Ltd. All rights reserved

Aerosol mapping over land with imaging spectroscopy using spectral autocorrelation

A new method for aerosol retrieval over land is proposed that makes explicit use of the contiguous, high-resolution spectral coverage of imaging spectrometers. The method is labelled Aerosol Retrieval by Interrelated Abundances (ARIA) and is based on unmixing of the short-wave infrared sensor signal by region-specific endmembers, assuming low aerosol radiative influence in this spectral region. Derived endmember abundances are transferred to the visible part of the spectrum in order to approximate surface reflectance where aerosol influence is generally strongest. Spectral autocorrelation of surface spectra is a precondition for ARIA and demonstrated using a reference spectrum database. The re-mixed surface reflectance is used as input quantity for the inversion of aerosol optical depth tau(a) at 0.55 mum wavelength on a pixel basis. Except for the choice of endmembers and the atmospheric vertical profile, no a priori assumptions on the image scene are required. The potential of the presented method for aerosol retrieval is demonstrated for an Airborne Visible/ Infrared Imaging Spectrometer (AVIRIS) scene, collected in California in 2000. Comparisons with existing aerosol retrieval methods showed encouraging results in terms of achieved spatial smoothness and degree of uncertainty of aerosol optical depth across the scene