Infrared Continuum Absorption by Atmospheric Water Vapor in the 8-12- Micrometer Window PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages : 29
Book Description
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: Publisher: ISBN: Category : Languages : en Pages : 29
Book Description
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: G. L. Loper Publisher: ISBN: Category : Languages : en Pages : 99
Book Description
Described are the results of a laboratory study of the weak water-continuum absorption within the 8- to 12-micrometer atmospheric transmission window. The highly sensitive photoacoustic detection technique was used in conjunction with a line-tunable CO2 laser to measure water continuum absorption throughout the CO2 laser 10.4-micrometer band. These measurements were performed over a range of atmospheric temperatures and water pressures important to the attenuation of radiation for long-slant atmospheric transmission paths. Water continuum CO2 laser absorption spectra are reported for temperatures between 27 and -10 deg C. Below room temperature, spectra of this type have not been determined previously. The water continuum absorption was found to possess a negative temperature dependence between 27 and -10 deg C that is similar to that observed between 100 and 27 deg C by previous investigators. The temperature, pressure, and wavelength dependences observed for the 8- to 12-micrometer water continuum in this study, and in previous studies reviewed thoroughly here, are best modeled by assuming simultaneous contributions of water-dimer and collisional-broadening mechanisms to the continuum. At room temperature and below, the water dimer mechanism becomes more important than the collisional-broadening mechanism.
Author: Robert Paul D'Entremont Publisher: ISBN: Category : Attenuation (Physics) Languages : en Pages : 50
Book Description
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: Adarsh Deepak Publisher: Elsevier ISBN: 1483273342 Category : Science Languages : en Pages : 712
Book Description
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: Michael Eugene Thomas Publisher: ISBN: Category : Infrared spectroscopy Languages : en Pages : 468
Book Description
Attenuation of infrared radiation in the troposphere is dominated by water vapor absorption. Most past work on the spectroscopy of water vapor has been on the analysis of the rotational and vibrational bands. As a result a thorough listing of line positions, line strengths and halfwidths exists today. Because of the weak 'continuum' absorption in the water vapor windows centered at 10 and 4 microns, efforts to measure and model the continuum have not been as successful as efforts in the analysis of the bands. Yet a precise understanding of continuum absorption is important for long path energy transmission. The purpose of this study is to demonstrate the importance of far wing phenomena in characterizing H2O continuum absorption. A total line shape for water vapor-nitrogen interactions valid under tropospheric conditions is derived. The model is tested using a set of experimental room temperature H2O continuum measurements of high quality. Using this data base parameters of the far wing component of the total line shape are determined.
Author: J. E. A. Selby Publisher: ISBN: Category : Aerosols Languages : en Pages : 86
Book Description
This supplement provides several additions and updates to the LOWTRAN 3 computer code, which can be used to calculate the transmittance of the atmosphere from the ultraviolet to the middle infrared portion of the spectrum (0.25 to 28.5 micrometers) at a spectral resolution of 20 cm. The major additions are the inclusion of water vapor continuum attenuation in the 3.5 to 4.2 micrometers region, and a temperature dependence to the H2O continuum attenuation coefficient in both the 4 micrometers and 10 micrometers regions. The contribution of foreign gas broadening in the 8-14 micrometers region has also been reduced. Four aerosol models are included in this supplement. These include three boundary layer aerosol models for maritime, urban, and rural conditions in the lower 2 km of the atmosphere, and a tropospheric model for use mainly above 1 or 2 km altitude. The rural model is a replacement for the average continental model presently in LOWTRAN 3. A temporary provision is also given to accommodate fog conditions when the visual range falls below 2 km. (Author).
Author: Michael P. Weinreb Publisher: ISBN: Category : Atmospheric radiation Languages : en Pages : 48
Book Description
"We describe a method of simulating measurements of atmospheric radiances and brightness temperatures in wide-bank window channels (at 11 and 3.7 um) of satellite radiometers. As input the simulation takes vertical profiles of atmospheric temperature and water-vapor mixing ratio, as well as the spectral response functions of the window channels. It models the atmospheric transmittances and integrates the equation of radiative transfer. We demonstrate the use of the method with applications to the Advanced Very High Resolution Radiometer on the TIROS-N satellite."--p.1.
Author: Environmental Research Institute of Michigan. Infrared Information and Analysis Center Publisher: ISBN: Category : Infrared radiation Languages : en Pages : 1740
Author: 
Author: 
Author: G. L. Loper
Author: G. L. Loper
Author: Robert Paul D'Entremont
Author: Adarsh Deepak
Author: Michael Eugene Thomas
Author: Hugh R. Carlon
Author: J. E. A. Selby
Author: Michael P. Weinreb
Author: Environmental Research Institute of Michigan. Infrared Information and Analysis Center