Water vapour self-continuum and water dimers: 1. Analysis of recent work

Ptashnik, Igor V.; Shine, Keith P.; Vigasin, A. A.

doi:10.1016/j.jqsrt.2011.01.012

Cited by 109 publications

(114 citation statements)

References 66 publications

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“…The last column of O 2 ) results [30] to account for a larger band width of 60 cm −1 (compared with 40 cm −1 in Kjaergaard et al [30]). The latter was found to be a reasonably good first approximation for water dimer Lorentzian sub-bands to describe the self-continuum spectral features within near-infrared bands [11][12][13][14], and even the strength of the continuum in the windows [14,16] at close to standard temperatures. As a result, there is quite good agreement between the radiative impact of the experimental self-and foreign CAVIAR continuum (column 3) and the modified results of Kjaergaard et al [30] for H 2 O complexes (last column in table 4) made using their assumption of Lorentzian wings.…”

Section: Implication For Near-infrared Absorption By the Atmospherementioning

confidence: 89%

“…Moreover, for such small dissociation energies, 3 Strictly speaking, the term 'CIA', by its origin, should be used only for BA arising mostly from transitions not involving long-lived quasi-bound and true-bound states [26]. Hence, until an exact partitioning of pair states is performed, using a general term 'bimolecular absorption' could be more advisable [14]. At the same time, traditionally the term 'CIA' is often used with respect to BA spectra in the region of the dipole-forbidden transition in the highly symmetrical parent monomers (such as N 2 in the discussion above).…”

Section: Discussionmentioning

confidence: 99%

“…The weak local out-of-band combinational + librational sub-bands of these complexes may also make some contribution within the windows. Finally, at different temperatures, there may be different dominant contributors to the out-of-band foreign continuum: from true bound and quasibound complexes to the free-pair collisions (which also include far wings of monomer lines) [14]. All these considerations may complicate the situation and make it impossible to apply a general (for example, across a broad temperature range) description of the out-of-band continuum using just a simple Lorentzian band-width approach.…”

Section: Implication For Near-infrared Absorption By the Atmospherementioning

confidence: 99%

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Water vapour foreign-continuum absorption in near-infrared windows from laboratory measurements

Ptashnik

McPheat

Shine

et al. 2012

Phil. Trans. R. Soc. A.

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For a long time, it has been believed that atmospheric absorption of radiation within wavelength regions of relatively high infrared transmittance (so-called 'windows') was dominated by the water vapour self-continuum, that is, spectrally smooth absorption caused by H 2 O−H 2 O pair interaction. Absorption due to the foreign continuum (i.e. caused mostly by H 2 O−N 2 bimolecular absorption in the Earth's atmosphere) was considered to be negligible in the windows. We report new retrievals of the water vapour foreign continuum from high-resolution laboratory measurements at temperatures between 350 and 430 K in four near-infrared windows between 1.1 and 5 mm (9000-2000 cm −1 ). Our results indicate that the foreign continuum in these windows has a very weak temperature dependence and is typically between one and two orders of magnitude stronger than that given in representations of the continuum currently used in many climate and weather prediction models. This indicates that absorption owing to the foreign continuum may be comparable to the self-continuum under atmospheric conditions in the investigated windows. The calculated global-average clear-sky atmospheric absorption of solar radiation is increased by approximately 0.46 W m −2 (or 0.6% of the total clearsky absorption) by using these new measurements when compared with calculations applying the widely used MTCKD (Mlawer-Tobin-Clough-Kneizys-Davies) foreigncontinuum model.

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Section: Implication For Near-infrared Absorption By the Atmospherementioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Implication For Near-infrared Absorption By the Atmospherementioning

confidence: 99%

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Water vapour foreign-continuum absorption in near-infrared windows from laboratory measurements

Ptashnik

McPheat

Shine

et al. 2012

Phil. Trans. R. Soc. A.

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“…More recently, some of this effort was focused on potential atmospheric impact of the water dimer (e.g., Refs. [16][17][18][19]. Most laboratory experiments concentrated on the lower spectral energy ranges.…”

mentioning

confidence: 99%

Communication: A rotationally resolved (2OH) overtone band in the water dimer (H2O)2

Földes

Vanfleteren

Herman

2014

The Journal of Chemical Physics

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“…MT_CKD also appears to underestimate the strength of the continuum in some high-transmittance atmospheric windows by as much as an order of magnitude [10]. A unifying theory of the continuum is still lacking, with competing formulations based on the far wings of water lines [11] and on the existence of bimolecular complexes known as dimers [3]. A revived interest in dimers has seen some recent papers [12] suggesting an important role for dimers in contributing to atmospheric absorption optical depths.…”

Section: Introductionmentioning

confidence: 99%

Airborne and satellite remote sensing of the mid-infrared water vapour continuum

Newman

Green

Ptashnik

et al. 2012

Phil. Trans. R. Soc. A.

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Remote sensing of the atmosphere from space plays an increasingly important role in weather forecasting. Exploiting observations from the latest generation of weather satellites relies on an accurate knowledge of fundamental spectroscopy, including the water vapour continuum absorption. Field campaigns involving the Facility for Airborne Atmospheric Measurements research aircraft have collected a comprehensive dataset, comprising remotely sensed infrared radiance observations collocated with accurate measurements of the temperature and humidity structure of the atmosphere. These field measurements have been used to validate the strength of the infrared water vapour continuum in comparison with the latest laboratory measurements. The recent substantial changes to self-continuum coefficients in the widely used MT_CKD (MlawerTobin-Clough-Kneizys-Davies) model between 2400 and 3200 cm −1 are shown to be appropriate and in agreement with field measurements. Results for the foreign continuum in the 1300-2000 cm −1 band suggest a weak temperature dependence that is not currently included in atmospheric models. A one-dimensional variational retrieval experiment is performed that shows a small positive benefit from using new laboratory-derived continuum coefficients for humidity retrievals.

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Water vapour self-continuum and water dimers: 1. Analysis of recent work

Cited by 109 publications

References 66 publications

Water vapour foreign-continuum absorption in near-infrared windows from laboratory measurements

Water vapour foreign-continuum absorption in near-infrared windows from laboratory measurements

Communication: A rotationally resolved (2OH) overtone band in the water dimer (H2O)2

Airborne and satellite remote sensing of the mid-infrared water vapour continuum

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