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Radiance Data (radiance + data)

Distribution by Scientific Domains

Earth and Environmental Science	66%

Selected Abstracts

Hyperspectral retrieval of land surface emissivities using ARIES

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 645 2009
Jean-Claude Thelen
Abstract Here we demonstrate the feasibility of applying a fast radiative transfer code, based on empirical orthogonal functions, in conjunction with a 1D-Var physical retrieval system to hyperspectral data taken from space/airborne radiance measurements in order to retrieve the emissivity spectra of the underlying surface. This approach was successfully tested using hyperspectral data obtained during the JAIVEx campaign in 2007 with the Airborne Research Interferometer Evaluation System (ARIES) on board of the UK Atmospheric Research aircraft. Using ARIES has the advantage that, during low-level flights, the surface emissivities can be derived directly from the hyperspectral data. Thus ARIES is capable of providing both the hyperspectral radiance data and the ,true' surface emissivity which has obvious advantages for validating the retrieval of the surface emissivity spectra. © Crown Copyright 2009. Published by John Wiley & Sons, Ltd. [source]

Assimilation of Meteosat radiance data within the 4D-Var system at ECMWF: Assimilation experiments and forecast impact

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 601 2004
Christina Köpken
Abstract The direct assimilation of water vapour (WV) clear-sky radiances (CSRs) from geostationary satellites within the ECMWF four-dimensional variational assimilation (4D-Var) became operational on 9 April 2002 with the assimilation of radiances from Meteosat-7. To extend the coverage provided by geostationary radiances, the derivation of a similar CSR product from the Geostationary Operational Environmental Satellites GOES-W and GOES-E was initiated and since 14 January 2003 these data have been operationally assimilated as well. This paper discusses results from the pre-operational impact experiments using Meteosat-7 and the subsequent operational implementation of the WV radiance assimilation. The pre-operational data monitoring of the CSRs shows contamination of certain time slots caused by intruding solar stray light and a certain degree of cloud influence present in the CSR. Data quality control is introduced to exclude affected data. When assimilated, the Meteosat WV CSRs correct the upper-tropospheric humidity field in areas of known model problems. While the analysis draws well to Meteosat data, the fit to other conventional observations does not degrade, and the fit to other satellite observations is noticeably improved. This is visible in statistics for the assimilated HIRS-12 as well as for passive Advanced Microwave Sounding Unit B (AMSUB) radiances, both in the pre-operational experiments and in the operational assimilation cycle. The impact on forecast quality is slightly positive to neutral for different areas of the globe. In some experiments a positive impact on upper-level wind fields (around 200 hPa) is seen, especially in the tropics. A relatively large sensitivity is noted of the mean increments and also forecast scores to the bias correction. Copyright © 2004 Royal Meteorological Society [source]

On the radiative properties of cirrus cloud at solar and thermal wavelengths: A test of model consistency using high-resolution airborne radiance measurements

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 598 2004
A. J. Baran
Abstract Two models describing the single-scattering properties of cirrus cloud are tested for physical consistency at solar and thermal wavelengths using airborne high-resolution radiance data. The data were obtained from a case of semi-transparent cirrus cloud, which occurred north of Scotland during October 2000. The single-scattering models tested are randomly oriented hexagonal ice columns and randomly oriented ice aggregates. High-spectral resolution radiances were measured from above the cirrus at a number of wavelengths between 0.3 and 16.7 µm, thereby covering a large range of ice crystal size parameter space and complex refractive index. It is shown that consistency between retrieved optical thickness and ice crystal effective radius at both solar and infrared wavelengths could only be achieved if the ice aggregate model was assumed. Moreover, differences between the ice aggregate model and spectrally resolved brightness temperature measurements were generally well within ±1 K between the wavelengths of 3.3 and 16.0 µm in the clean atmospheric window regions. The paper shows that it is important to have simultaneous radiance measurements from both the solar and thermal spectral regions so that ice crystal scattering models and cirrus retrievals can be rigorously tested. © Crown copyright 2004. [source]

A new IR technique for monitoring low cloud properties using geostationary satellite data

ATMOSPHERIC SCIENCE LETTERS, Issue 2 2009
Qingyuan Han
Abstract A new technique of using satellite infrared radiance data for retrieving cloud properties is developed and applied to SEVIRI data, which is based on direct radiative transfer calculations, not on the emissivity approximation as used by other satellite IR only techniques. Instantaneous atmospheric profiles are used in the new technique for improving the accuracy of retrievals. Comparison of the retrieved results with coincident observations of CloudSat and CALIPSO shows excellent agreement for low clouds. This study shows that, using only IR radiances, the single layer assumption would significantly underestimate cloud optical depth when multilayered cloud system is presented. Copyright © 2009 Royal Meteorological Society [source]

An improved method for correcting radiance data for bandpass error

COLOR RESEARCH & APPLICATION, Issue 5 2010
Hugh S. Fairman
Abstract Methods have previously been proposed for correction of measured radiance data for bandpass error. These proposals are reviewed and a recommendation is made of a method for making this deconvolution of the measured data to corrected spectral data. The method consists of three separate treatments of passbands. First, the first and last measured passbands are treated by one process. Then the second and next-to-last interior passbands are treated by another process. All remaining interior passbands are then treated by a third process. The results of doing so are reported and compared with two other methods of making the correction that have appeared in the literature. © 2009 Wiley Periodicals, Inc., Col Res Appl, 2010. [source]