The inclusion of the MT_CKD water vapor continuum model in the HITRAN molecular spectroscopic database

Mlawer, E. J.; Cady‐Pereira, Karen; Mascio, J.; Gordon, Iouli E.

doi:10.1016/j.jqsrt.2023.108645

Cited by 18 publications

(12 citation statements)

References 33 publications

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“…Nevertheless, experimental studies disagree on how strongly continuum absorption decreases with warming (Cormier et al, 2005), and the physical mechanisms underlying the mid-infrared water vapor continuum-whether related primarily to water vapor dimers or to far wings of strong lines in rotational and rotational-vibrational bands-still remain controversial (e.g., Shine et al, 2012). Furthermore, the temperature-dependence of the water vapor self-continuum in MT_CKD has recently been updated (Mlawer et al, 2023), though it is not clear how much of an impact this might have on our results. Overall, uncertainty in water vapor continuum absorption could affect Δ T , especially at high temperatures where the impact of the continuum region is strongest.…”

Section: Discussionmentioning

confidence: 99%

How Well do We Understand the Planck Feedback?

Cronin¹

2023

J Adv Model Earth Syst

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A reference or “no‐feedback” radiative response to warming is fundamental to understanding how much global warming will occur for a given change in greenhouse gases or solar radiation incident on the Earth. The simplest estimate of this radiative response is given by the Stefan‐Boltzmann law as −4σTe‾3≈−3.8 ${-}4\sigma {\overline{{T}_{e}}}^{3}\approx -3.8$ W m−2 K−1 for Earth's present climate, where trueTe‾ $\overline{{T}_{e}}$ is a global effective emission temperature. The comparable radiative response in climate models, widely called the “Planck feedback,” averages −3.3 W m−2 K−1. This difference of 0.5 W m−2 K−1 is large compared to the uncertainty in the net climate feedback, yet it has not been studied carefully. We use radiative transfer models to analyze these two radiative feedbacks to warming, and find that the difference arises primarily from the lack of stratospheric warming assumed in calculations of the Planck feedback (traditionally justified by differing constraints on and time scales of stratospheric adjustment relative to surface and tropospheric warming). The Planck feedback is thus masked for wavelengths with non‐negligible stratospheric opacity, and this effect implicitly acts to amplify warming in current feedback analysis of climate change. Other differences between Planck and Stefan‐Boltzmann feedbacks arise from temperature‐dependent gas opacities, and several artifacts of nonlinear averaging across wavelengths, heights, and different locations; these effects partly cancel but as a whole slightly destabilize the Planck feedback. Our results point to an important role played by stratospheric opacity in Earth's climate sensitivity, and clarify a long‐overlooked but notable gap in our understanding of Earth's reference radiative response to warming.

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Section: Discussionmentioning

confidence: 99%

How Well do We Understand the Planck Feedback?

Cronin¹

2023

J Adv Model Earth Syst

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“…We provide here background information concerning our understanding of water vapor continuum absorption in the infrared window and its development over the last several decades, including its treatment in the Mlawer-Tobin_Clough-Kneizys-Davies (MT_CKD) water vapor continuum ] Change in OLR model (Mlawer et al, 2023;Mlawer et al, 2012), the primary source used in the community to specify water vapor continuum absorption in this spectral region. For reference, self and foreign continuum optical depths from the current version of MT_CKD (v4.1.1) are shown in Fig.…”

Section: The Water Vapor Continuum In the Infrared Windowmentioning

confidence: 99%

“…The MT_CKD water vapor continuum model (Mlawer et al, 2023;Mlawer et al, 2012) provides water vapor self and foreign continuum coefficients (cm 2 /molecule/cm -1 ) every 10 cm -1 from 0-20,000 cm -1 . To obtain continuum coefficients in between the stored values, a cubic interpolation using the four closest stored values is performed.…”

Section: Model Calculationsmentioning

confidence: 99%

“…For our study, we use the TROPoe (Turner & Löhnert, 2014) physical retrieval algorithm to retrieve profiles of temperature and humidity that provide closure with the sonde profiles, the AERI radiance observations between 538 and 722 cm -1 (i.e., regions of the spectrum wherein the water vapor line shape and continuum absorption have undergone validation Mlawer et al, 2019), and the brightness temperatures at 23.8 and 31.4 GHz from a microwave radiometer (MWR;. For this study, the TROPoe retrieval utilizes the latest version of the MT_CKD continuum (Mlawer et al, 2023) and the AER line file, ensuring that its water vapor spectroscopy from 538-722 cm -1 includes recent upgrades.…”

Section: Input To the Modelmentioning

confidence: 99%

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A More Transparent Infrared Window

Mlawer,

Mascio,

Turner

et al. 2024

Preprint

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The infrared window region (780-1250 cm-1, 12.8 to 8.0 µm) is of great importance to Earth’s climate due to its high transparency and thermal energy. We present here a new investigation of the transparency of this spectral region based on observations by interferometers of downwelling surface radiance at two DOE Atmospheric Radiation Measurement program sites. We focus on the dominant source of absorption in this region, the water vapor continuum, and derive updated values of spectral absorption coefficients for both the self and foreign continua. Our results show that the self continuum is too strong in the previous version of Mlawer-Tobin_Clough-Kneizys-Davies (MT_CKD) water vapor continuum model, a result that is consistent with other recent analyses, while the foreign continuum is too weak in MT_CKD. In general, the weaker self continuum derived in this study results in an overall increase in atmospheric transparency in the window, although in atmospheres with low amounts of water vapor the transparency may slightly decrease due to the increase in foreign continuum absorption. These continuum changes lead to a significant decrease in downwelling longwave flux at the surface for moist atmospheres and a modest increase in outgoing longwave radiation. The increased fraction of surface-leaving radiation that escapes to space leads to a notable increase (~5-10%) in climate feedback, implying that climate simulations that use the new infrared window continuum will show somewhat less warming than before. This study also points out the possibly important role that aerosol absorption may play in the longwave radiative budget.

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“…Nowadays, the most popular and only global semi-empirical continuum model is MT_CKD. 23,24 It yields the values of a continuum in the entire range of electromagnetic waves significant for the Earth radiation balance (from 0 to 20 000 cm −1 ). The model includes (i) the so-called “weak interaction term” which, in the opinion of the authors of ref.…”

Section: Introductionmentioning

confidence: 99%

On the nature of sub-THz continuum absorption in CO₂ gas, its mixture with Ar, and in pure water vapor

Galanina,

Koroleva,

Amerkhanov

et al. 2024

Phys. Chem. Chem. Phys.

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The inclusion of the MT_CKD water vapor continuum model in the HITRAN molecular spectroscopic database

Cited by 18 publications

References 33 publications

How Well do We Understand the Planck Feedback?

How Well do We Understand the Planck Feedback?

A More Transparent Infrared Window

On the nature of sub-THz continuum absorption in CO₂ gas, its mixture with Ar, and in pure water vapor

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The inclusion of the MT_CKD water vapor continuum model in the HITRAN molecular spectroscopic database

Cited by 18 publications

References 33 publications

How Well do We Understand the Planck Feedback?

How Well do We Understand the Planck Feedback?

A More Transparent Infrared Window

On the nature of sub-THz continuum absorption in CO2 gas, its mixture with Ar, and in pure water vapor

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On the nature of sub-THz continuum absorption in CO₂ gas, its mixture with Ar, and in pure water vapor