The water vapour self- and water–nitrogen continuum absorption in the 1000 and 2500 cm
            <sup>−1</sup>
            atmospheric windows

Baranov, Yu. I.; Lafferty, W. J.

doi:10.1098/rsta.2011.0234

Cited by 49 publications

(35 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Although there is a general dearth of continuum measurements with which to compare, the CAVIAR self‐ and foreign‐ continua in the 3.8 µm window measurements agree, within the uncertainties, with the laboratory measurements of Baranov () and Baranov and Lafferty (), as well as with some earlier self‐continuum measurements reported in Ptashnik et al (); the older measurements of Burch and Alt () are lower than the newer laboratory measurements in the centre of the window by a factor of about 6 at near‐room temperature (and are lower than the empirically adjusted MT_CKD_2.5 by around a factor of 3), but are in much better agreement at higher temperatures. In the 2.1 and 3.8 µm windows, measurements involving some of the CAVIAR authors, but made using somewhat different experimental set‐ups to those used in CAVIAR (all used the same type of Fourier Transform Spectrometer, but different long and short pathlength gas cells are used), support the CAVIAR results (Paynter et al , ; Ptashnik et al , ), although they are higher than the Bicknell et al () measurements in the centre of the 2.1 µm window by about a factor of 4.…”

Section: Introductionsupporting

confidence: 77%

Global radiative and climate effect of the water vapour continuum at visible and near‐infrared wavelengths

Rädel

Shine

Ptashnik

2014

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

Recent laboratory measurements show that absorption by the water vapour continuum in near-infrared windows may be about an order of magnitude higher than assumed in many radiation codes. The radiative impact of the continuum at visible and near-infrared wavelengths is examined for the present day and for a possible future warmer climate (with a global-mean total column water increase of 33%). The calculations use a continuum model frequently used in climate models ('CKD') and a continuum model where absorption is enhanced at wavelengths greater than 1 μm based on recent measurements ('CAVIAR'). The continuum predominantly changes the partitioning between solar radiation absorbed by the surface and the atmosphere; changes in top-of-atmosphere net irradiances are smaller. The global-mean clear-sky atmospheric absorption is enhanced by 1.5 W m −2 (about 2%) and 2.8 W m −2 (about 3.5%) for CKD and CAVIAR respectively, relative to a hypothetical no-continuum case, with all-sky enhancements about 80% of these values. The continuum is, in relative terms, more important for radiation budget changes between the present day and a possible future climate. Relative to the no-continuum case, the increase in globalmean clear-sky absorption is 8% higher using CKD and almost 20% higher using CAVIAR; all-sky enhancements are about half these values. The effect of the continuum is estimated for the solar component of the water vapour feedback, the reduction in downward surface irradiance and precipitation change in a warmer world. For CKD and CAVIAR respectively, and relative to the no-continuum case, the solar component of the water vapour feedback is enhanced by about 4 and 9%, the change in clear-sky downward surface irradiance is 7 and 18% more negative, and the global-mean precipitation response decreases by 1 and 4%. There is a continued need for improved continuum measurements, especially at atmospheric temperatures and at wavelengths below 2 μm.

show abstract

Section: Introductionsupporting

confidence: 77%

Global radiative and climate effect of the water vapour continuum at visible and near‐infrared wavelengths

Rädel

Shine

Ptashnik

2014

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

show abstract

“…For example, Paynter and Ramaswamy [] showed that the water vapor continuum could result in between 1.1 W m −2 and 3.2 W m −2 additional clear‐sky absorption of solar radiation globally. This sizable range is due to fairly large measurement uncertainties in the shortwave near‐infrared window regions [ Ptashnik et al ., , , , ; Paynter et al ., , ; Baranov and Lafferty , , ; Mondelain et al ., ]. These uncertainties along with a comprehensive history of the water vapor continuum in both the longwave and shortwave has previously been described by Shine et al .…”

Section: Introductionmentioning

confidence: 99%

Investigating the impact of the shortwave water vapor continuum upon climate simulations using GFDL global models

Paynter

Ramaswamy

2014

J. Geophys. Res. Atmos.

View full text Add to dashboard Cite

We have added the BPS-MTCKD 2.0 parameterization for the shortwave water vapor continuum to the Geophysical Fluid Dynamics Laboratory (GFDL) global model. We find that inclusion of the shortwave continuum in the fixed sea surface temperature case (AM3) results in a similar increase in shortwave absorption and heating rates to that seen for the "benchmark" line-by-line radiative transfer calculations. The surface energy budget adjusts to the inclusion of the shortwave continuum predominantly through a decrease in both surface latent and sensible heat. This leads to a decrease in tropical convection and a subsequent 1% reduction in tropical rainfall. The inclusion of the shortwave continuum in the fully coupled atmosphere-ocean model (CM3) yields similar results, but a smaller overall reduction of 0.5% in tropical rainfall due to global warming of~0.1 K linked to enhanced near-infrared absorption. We also investigated the impact of adding a stronger version of BPS-MTCKD (version 1.1) to the global climate model (GCM). In most cases we found that the GCM responds in a similar manner to both continua but that the strength of the response scales with the level of absorbed shortwave radiation. Global warming experiments were run in both AM3 and CM3. The shortwave continuum was found to cause a 7 to 15% increase in clear-sky global dimming depending upon whether the stronger or weaker continuum version was used. Neither version resulted in a significant change to the climate sensitivity.

show abstract

“…New laboratory measurements of the continuum owing to water-air mixtures in the near-infrared windows by Ptashnik et al [4] indicate that absorption is up to about 100 times stronger than given by the semi-empirical models. Baranov & Lafferty [5] present new observations of the continuum at 4 and 10 mm; while the differences with the semi-empirical models are greatest at the shorter wavelengths, the work stresses that, even in the better characterized mid-infrared region, the semi-empirical models still do not fully reproduce the observed spectral and temperature dependence.…”

Section: Water In the Gas Phasementioning

confidence: 96%

Water in the gas phase

Tennyson

Shine

2012

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

Switch on the weather forecast any evening and one is left in no doubt as to the importance of water in the Earth's atmosphere: will the water be gaseous (humidity), liquid (clouds, rain), solid (snow, ice or hail) or taken up by aerosol (haze) particles? The long-term role of water in our climate, and of course any change in our climate, is no less profound. The water vapour is both the dominant absorber of incoming sunlight and the major greenhouse gas, so any climate model has to adequately account for its behaviour.While many aspects of how the water molecule absorbs and emits light in our atmosphere are becoming increasingly well understood, some remain scientifically challenging. For example, a thorough understanding of the actual shape of individual water absorption lines is crucial for correctly modelling absorption by water vapour. This is necessary not only for climatic reasons but also because many remote sensing experiments, both space and ground based, require a detailed understanding of this absorption so that the characteristic signatures of other, trace species can be recovered. As discussed by Ngo et al. [1], there is now incontrovertible evidence that the true line shape, at line centre and in the near wings, departs significantly from the Voigt profile that has traditionally been used to represent the change in water line profiles as a function of temperature and pressure. However, what one should use instead of Voigt profiles remains a matter for debate, which is informed by high-precision experiments such as those reported by Hodges et al. [2].The radiative impact of atmospheric water vapour (and its role in remote sensing) depends not only on the tens of thousands of individual absorption lines but also on the so-called water vapour continuum, which varies relatively smoothly with wavelength from visible to microwave wavelengths. The continuum has been most intensively studied in the mid-infrared 'window' (wavelengths from approx. 8 to 12 mm) but, outside of this region, its strength and temperature dependence, particularly in atmospheric conditions, are less well characterized. In addition, there has been a long-lasting and robust debate as to the underlying cause of the continuum, it probably being due to some combination of the far wings of individual spectral lines of the water monomer and absorption owing to water dimers and other bimolecular complexes (e.g. H 2 O-N 2 ). Many radiative transfer codes used in weather prediction and climate models use the semi-empirical representation of the water vapour continuum from the CKD (Clough-Kneizys-Davies) and MT_CKD (Mlawer-Tobin-Clough-Kneizys-Davies) family of models; Mlawer et al. [3] provide a detailed description of the newest version of this model and describe how One contribution of 17 to a Theo Murphy Meeting Issue 'Water in the gas phase'.

show abstract

The water vapour self- and water–nitrogen continuum absorption in the 1000 and 2500 cm ⁻¹ atmospheric windows

Cited by 49 publications

References 37 publications

Global radiative and climate effect of the water vapour continuum at visible and near‐infrared wavelengths

Global radiative and climate effect of the water vapour continuum at visible and near‐infrared wavelengths

Investigating the impact of the shortwave water vapor continuum upon climate simulations using GFDL global models

Water in the gas phase

Contact Info

Product

Resources

About

The water vapour self- and water–nitrogen continuum absorption in the 1000 and 2500 cm −1 atmospheric windows

Cited by 49 publications

References 37 publications

Global radiative and climate effect of the water vapour continuum at visible and near‐infrared wavelengths

Global radiative and climate effect of the water vapour continuum at visible and near‐infrared wavelengths

Investigating the impact of the shortwave water vapor continuum upon climate simulations using GFDL global models

Water in the gas phase

Contact Info

Product

Resources

About

The water vapour self- and water–nitrogen continuum absorption in the 1000 and 2500 cm ⁻¹ atmospheric windows