Interpretation of the water vapour continuum absorption spectra in 0.94 and 1.13 micron bands taking into account the contribution from intermediate line wings

Water vapour continuum absorption is an important contributor to the Earth's radiative cooling and energy balance. Here, we describe the development and status of the MT_CKD (MlawerTobinCloughKneizysDavies) water vapour continuum absorption model. The perspective adopted in developing the MT_CKD model has been to constrain the model so that it is consistent with quality analyses of spectral atmospheric and laboratory measurements of the foreign and self continuum. For field measurements, only cases for which the characterization of the atmospheric state has been highly scrutinized have been used. Continuum coefficients in spectral regions that have not been subject to compelling analyses are determined by a mathematical formulation of the spectral shape associated with each water vapour monomer line. This formulation, which is based on continuum values in spectral regions in which the coefficients are well constrained by measurements, is applied consistently to all water vapour monomer lines from the microwave to the visible. The results are summed-up (separately for the foreign and self) to obtain continuum coefficients from 0 to 20 000 cm −1 . For each water vapour line, the MT_CKD line shape formulation consists of two components: exponentially decaying far wings of the line plus a contribution from a water vapour molecule undergoing a weak interaction with a second molecule. In the MT_CKD model, the first component is the primary agent for the continuum between water vapour bands, while the second component is responsible for the majority of the continuum within water vapour bands. The MT_CKD model should be regarded as a semi-empirical model with strong constraints provided by the known physics. Keeping the MT_CKD continuum consistent with current observational studies necessitates periodic updates to the water vapour continuum coefficients. In addition to providing details on the MT_CKD line shape formulation, we describe the most recent update to the model, MT_CKD_2.5, which is based on an analysis of satellite- and ground-based observations from 2385 to 2600 cm −1 (approx. 4 μm).

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The infra-red absorption spectra of quartz and fused Silica from 1 to 7·5 μ II-Experimental results

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1936.0005 ◽

1936 ◽

Vol 153 (879) ◽

pp. 328-339 ◽

Cited By ~ 33

Keyword(s):

Water Vapour ◽

Absorption Spectra ◽

Wave Length ◽

Fused Silica ◽

Experimental Results ◽

Wave Number ◽

Infra Red ◽

The Mean ◽

Point To Point ◽

Maximum Discrepancy

The accuracy of calibration, as already mentioned, was checked against CO 2 and water vapour bands. With the quartz prism the instrument could be set to show the 2·7 μ CO 2 bands resolved and within about 0·003μ of their known wave-lengths*; i. e., within 4 cm -1 . With the fluorite prism, resolution at 2·7 μ was inferior, but the structure of the water vapour band centred at 6·3 μ provided about 20 points for the checking of wave-lengths. Here the maximum discrepancy was 5 cm -1 and the mean discrepancy about 1·5 cm -1 , The wave-number error, therefore, is not libels to exceed 5 cm -1 in any part of the range investigated. The fraction of radiation transmitted by a specimen was measured to three figures and a mean of two or three observations at least taken for each wave-length setting. The accuracy varies from specimen to specimen and from point to point throughout the spectrum, depending on the magnitude of the galvanometer deflexions obtainable. The error is, however, nowhere likely to be greater than 0·01 and for much of the work is of the order of 0·002.

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Application of φ-IASI to IASI: retrieval products evaluation and radiative transfer consistency

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-8771-2009 ◽

2009 ◽

Vol 9 (22) ◽

pp. 8771-8783 ◽

Cited By ~ 30

Author(s):

G. Masiello ◽

C. Serio ◽

A. Carissimo ◽

G. Grieco ◽

M. Matricardi

Keyword(s):

Water Vapour ◽

Forward Model ◽

Continuum Absorption ◽

Weather Forecasts ◽

Time Profiles ◽

Spectral Residual ◽

Atmospheric Sounding ◽

Medium Range ◽

Temperature Water

Abstract. Retrieval products for temperature, water vapour and ozone have been obtained from spectral radiances measured by the Infrared Atmospheric Sounding Interferometer flying onboard the first European Meteorological Operational satellite. These products have been used to check the consistency of the forward model and its accuracy and the expected retrieval performance. The study has been carried out using a research-oriented forward-inverse methodology, called φ-IASI, that the authors have specifically developed for the new sounding interferometer. The performance of the forward-inversion strategy has been assessed by comparing the retrieved profiles to profiles of temperature, water vapour and ozone obtained by co-locating in space and time profiles from radiosonde observations and from the European Centre for Medium-Range Weather Forecasts analysis. Spectral residuals have also been computed and analyzed to assess the quality of the forward model. Two versions of the high-resolution transmission molecular absorption database have been used, which mostly differ for ozone absorption line parameters, line and continuum absorption of both CO2 and H2O molecules. Their performance has been assessed by inter-comparing the results, and a consistent improvement in the spectral residual has been found when using the most updated release.

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An investigation of the absorption spectra of water and ice, with reference to the spectra of the major planets

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1928.0150 ◽

1928 ◽

Vol 120 (785) ◽

pp. 296-302 ◽

Cited By ~ 3

Keyword(s):

Water Vapour ◽

Absorption Spectra ◽

Atomic Hydrogen ◽

Solar Spectrum ◽

High Dispersion ◽

The Sun ◽

Absorption Bands ◽

Weak Band ◽

General Similarity ◽

Dense Band

The spectra of the light of the sun reflected from the major planets—Jupiter, Saturn, Uranus and Neptune—were photographed by Slipher in 1909. These spectra showed a general similarity in that there were a number of absorption bands superimposed on the ordinary solar spectrum. The intensity and width of these absorptions varied from planet to planet, increasing in general from Jupiter to Neptune in the order quoted. Of the chemical identity of the bands little is known. Some—C and F, fig. 4, for example—can be attributed to absorption by atomic hydrogen in the atmospheres of the planets; others might be due to water-vapour, though other water-vapour bands do not appear. The outstanding unidentified bands which are common to the spectra of the four planets are (see fig. 4, Plate 10):— ( a ) At λ = 5430 Å.—A rather weak band in the spectra of Jupiter and Saturn, but very strong in those of Uranus and Neptune. ( b ) At λ = 6190 Å.—This is the mid-point of a conspicuous and dense band appearing in the spectra of all the four planets, broadening from a width of some 50 Å in that of Jupiter to some 200 Å in that of Neptune. Although quite strong in the spectrum of Jupiter, it showed no tendency to become resolved in the high dispersion plates taken of the spectrum of this planet. ( c ) A strong double band at λ = 7200 to 7260 Å recorded in the spectra of Saturn and Jupiter, and probably just as strong in those of Uranus and Neptune, but not recorded because of the insensitiveness of the plates in this region.

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