Quantification of the Infrared Water Vapor Continuum by Atmospheric Measurements PDF Download

Author: Andreas Reichert
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Hugh R. Carlon
Publisher:
ISBN:
Category : Atmospheric electricity
Languages : en
Pages : 0

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Publisher:
ISBN:
Category :
Languages : en
Pages : 29

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We have carried out a detailed analysis of several long-path-length transmission measurements in the 8 to 12 micrometer atmospheric window in order to determine the extinction coefficient due to the water vapor continuum. Our results indicate that three modifications to the current LOWTRAN atmospheric transmission model are required. The first two corrections are an improved fit to the pure water vapor continuum absorption coefficient and the elimination of the atmospheric broadened continuum term. Finally, and most critically, a strong measured temperature dependence must be included in the water vapor continuum absorption coefficient. For path lengths ranging from 10 to 50 km, failure to incorporate these corrections can lead to errors in the computed transmission ranging from factors of 2 to more than 10,000.

Author: Adarsh Deepak
Publisher: Elsevier
ISBN: 1483273342
Category : Science
Languages : en
Pages : 712

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Atmospheric Water Vapor contains the technical proceedings of the International Workshop on Atmospheric Water Vapor held in Vail, Colorado, on September 11-13, 1979. The papers assess the state-of-the-art in measurement, modeling, and application of atmospheric water vapor properties and highlight important problems that require further effort in order to better understand the atmosphere itself as well as the electromagnetic propagation through the atmosphere. Comprised of 39 chapters, this book begins with a discussion on the optics and spectroscopy of water vapor. Some actual spectra showing the problems specific to the water molecule are described, along with the method used to calculate precise vibration-rotation energy levels and wave functions. Atmospheric infrared transmission measurements in maritime locations are also presented. Subsequent sections explore microwave and millimeter wave phenomena; geoastrophysical applications; and in situ measurements, remote sensing, and meteorology of water vapor. The final chapters deal with the microphysics and atmospheric chemistry of water vapor. This monograph will be of interest to scientists from universities, government agencies, research laboratories, and industry.

Author: Hugh R. Carlon
Publisher:
ISBN:
Category : Atmospheric electricity
Languages : en
Pages : 33

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Author: Robert Paul D'Entremont
Publisher:
ISBN:
Category : Attenuation (Physics)
Languages : en
Pages : 50

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The Real-Time Nephanalysis (RTNE PH) generates real-time global analysis of cloud extent, base, height, and type. The RTNE PH makes extensive use of satellite data that are measured in the 10-12 micron infrared (IR) window for thermal mapping of clouds and the earth's surface both day and night. Water vapor absorption effects are significant in such data, especially for high viewing angles and tropical atmospheres where water vapor concentrations are generally high. Water vapor attenuates the emitted ground radiance, reducing its magnitude and with it the apparent temperature of the surface being viewed. Currently, the RTNEPH takes into account such attenuation losses using lookup tables that are functions of viewing geometry, time of day, type of background, and the like. However, these corrections have limited value and leave room for significant improvement. This report outlines and presents two new techniques that are expected to enhance the attenuation correction capabilities of the RTNEPH, multivariate polynomial regression (the Weinreb technique) and the correlated K method.

Author: Ralph Beeby
Publisher:
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Languages : en
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This thesis describes spectrally-resolved radiance measurements, recorded using the Imperial College-built Tropospheric Airborne Fourier Transform Spectrometer (TAFTS), to validate the current parameterisation of the far-infrared foreign- broadened continuum of atmospheric water vapour in line-by-line radiative transfer models. The current parameterisation is not based on measurement through the centre of the far-IR spectral region, but is constructed by interpolation from measurements either side of the band. Accurate knowledge of this parameterisation is essential as the far-IR contribution to the planetary outgoing longwave radiation (OLR) is significant. The research takes the form of a radiative closure study, comparing the radiance measurements with simulated radiances modelled using the measured atmospheric state (temperature, humidity) profile as input. The profile information was recorded, alongside the radiance measurements, aboard the UK Met Office / FAAM (Facility for Airborne Atmospheric Measurements) BAe-146 research aircraft, during the first of two field campaigns as part of the CAVIAR (Continuum Absorption in the Visible and Infrared and its Atmospheric Relevance) project. This thesis provides an overview of the relevant atmospheric physics and Fourier Transform Spectroscopy, including a description of TAFTS; the construction of the atmospheric profiles from the various in-situ, radiosonde and model datasets; the calibration of the radiances measured by TAFTS and derivation of the foreign- broadened water vapour continuum between 114- 540 cm-1 within the framework of the line-by-line radiative transfer model (LBLRTM v12.0). The resulting continuum is compared to other relevant recent studies. The measurements from this study suggest an increase in continuum strength up to 11 % at 238.6 cm -1, decreasing steadily to a reduction of 55 % at 114 cm -1 and 54 % at 513 cm-1. However, the uncertainties in these measurements are considerable, and might equally suggest an increase in continuum strength.

Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781723496301
Category :
Languages : en
Pages : 30

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A set of eleven measurements of the water vapor continuum absorption in the 840 to 1100 sq cm spectral region is reviewed and compared with spectral models maintained by the Air Force Geophysics Laboratory. The measurements were made in four different ways: spectrometer with a White cell, CO2 laser with a White cell, CO2 laser with a spectrophone, and broadband radiation source over a long atmospheric path. Where possible, the data were selected at a water vapor partial pressure of ten torr buffered to 760 torr with N2 or synthetic air and a temperature of between 296 and 300 K. The intercomparison of the data leads to several observations and conclusions. First, there are four sets of laboratory data taken with nitrogen as the buffer gas which generally agree well mutually and with AFGL's HITRAN code. Second, there is one set of laboratory data that shows that using air as the buffer gas gives a few percent decrease in the water vapor continuum compared with using nitrogen as the buffer gas. Third, the atmospheric long-path measurements for water vapor partial pressure below about 12 torr are roughly grouped within 20 percent of the HITRAN values. Fourth, there are three sets of spectrophone data for water vapor in synthetic air which are significantly higher than any of the other measurements. This discrepancy is attributed to the effects of impurity gases in the cell. Grant, William B. Jet Propulsion Laboratory NASA-CR-182361, JPL-PUBL-87-34, NAS 1.26:182361 NAS7-918; RTOP 644-11-00-03-78

Author: Jean-Michel Hartmann
Publisher: Elsevier
ISBN: 0128227362
Category : Science
Languages : en
Pages : 577

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Gas phase molecular spectroscopy is a powerful tool for obtaining information on the geometry and internal structure of isolated molecules and their interactions with others. It enables the understanding and description, through measurements and modeling, of the influence of pressure on light absorption, emission, and scattering by gas molecules, which must be taken into account for the correct analysis and prediction of the resulting spectra. Collisional Effects on Molecular Spectra: Laboratory Experiments and Models, Consequences for Applications, Second Edition provides an updated review of current experimental techniques, theoretical knowledge, and practical applications. After an introduction to collisional effects on molecular spectra, the book moves on by taking a threefold approach: it highlights key models, reviews available data, and discusses the consequences for applications. These include areas such as heat transfer, remote sensing, optical sounding, metrology, probing of gas media, and climate predictions. This second edition also contains, with respect to the first one, significant amounts of new information, including 23 figures, 8 tables, and around 700 references.Drawing on the extensive experience of its expert authors, Collisional Effects on Molecular Spectra: Laboratory Experiments and Models, Consequences for Applications, Second Edition, is a valuable guide for all those involved with sourcing, researching, interpreting, or applying gas phase molecular spectroscopy techniques across a range of fields. Provides updated information on the latest advances in the field, including isolated line shapes, line-broadening and -shifting, line-mixing, the far wings and associated continua, and collision-induced absorption Reviews recently developed experimental techniques of high accuracy and sensitivity Highlights the latest practical applications in areas such as metrology, probing of gas media, and climate prediction

Author: David Paynter
Publisher:
ISBN:
Category : Atmospheric radiation
Languages : en
Pages :

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