The HITRAN2012 molecular spectroscopic database

The HITRAN2016 molecular spectroscopic database

Session chairs

The HITRAN database is a compilation of molecular spectroscopic parameters. It was established in the early 1970s and is used by various computer codes to predict and simulate the transmission and emission of light in gaseous media (with an emphasis on terrestrial and planetary atmospheres). The HITRAN compilation is composed of five major components: the line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, experimental infrared absorption cross-sections (for molecules where it is not yet feasible for representation in a line-by-line form), collision-induced absorption data, aerosol indices of refraction, and general tables (including partition sums) that apply globally to the data. This paper describes the contents of the 2020 quadrennial edition of HITRAN. The HITRAN2020 edition takes advantage of recent experimental and theoretical data that were meticulously validated, in particular, against laboratory and atmospheric spectra. The new edition replaces the previous HITRAN edition of 2016 (including its updates during the intervening years).All five components of HITRAN have undergone major updates. In particular, the extent of the updates in the HITRAN2020 edition range from updating a few lines of specific molecules to complete replacements of the lists, and also the introduction of additional isotopologues and new (to HITRAN) molecules: SO, CH3F, GeH4, CS2, CH3I and NF3. Many new vibrational bands were added, extending the spectral coverage and completeness of the line lists. Also, the accuracy of the parameters for major atmospheric absorbers has been increased substantially, often featuring sub-percent uncertainties. Broadening parameters associated with the ambient pressure of water vapor were introduced to HITRAN for the first time and are now available for several molecules.The HITRAN2020 edition continues to take advantage of the relational structure and efficient interface available at www.hitran.org and the HITRAN Application Programming Interface (HAPI). The functionality of both tools has been extended for the new edition.

Abstract. Atmospheric radiative transfer models are extensively used in Earth observation to simulate radiative processes occurring in the atmosphere and to provide both upwelling and downwelling synthetic brightness temperatures for ground-based, airborne, and satellite radiometric sensors. For a meaningful comparison between simulated and observed radiances, it is crucial to characterize the uncertainty in such models. The purpose of this work is to quantify the uncertainty in radiative transfer models due to uncertainty in the associated spectroscopic parameters and to compute simulated brightness temperature uncertainties for millimeter- and submillimeter-wave channels of downward-looking satellite radiometric sensors (MicroWave Imager, MWI; Ice Cloud Imager, ICI; MicroWave Sounder, MWS; and Advanced Technology Microwave Sounder, ATMS) as well as upward-looking airborne radiometers (International Submillimetre Airborne Radiometer, ISMAR, and Microwave Airborne Radiometer Scanning System, MARSS). The approach adopted here is firstly to study the sensitivity of brightness temperature calculations to each spectroscopic parameter separately, then to identify the dominant parameters and investigate their uncertainty covariance, and finally to compute the total brightness temperature uncertainty due to the full uncertainty covariance matrix for the identified set of relevant spectroscopic parameters. The approach is applied to a recent version of the Millimeter-wave Propagation Model, taking into account water vapor, oxygen, and ozone spectroscopic parameters, though the approach is general and can be applied to any radiative transfer code. A set of 135 spectroscopic parameters were identified as dominant for the uncertainty in simulated brightness temperatures (26 for water vapor, 109 for oxygen, none for ozone). The uncertainty in simulated brightness temperatures is computed for six climatology conditions (ranging from sub-Arctic winter to tropical) and all instrument channels. Uncertainty is found to be up to few kelvins [K] in the millimeter-wave range, whereas it is considerably lower in the submillimeter-wave range (less than 1 K).

The HITRAN molecular spectroscopic database: edition of 2000 including updates through 2001

Several ultraviolet-visible (UV-VIS) spectral analysis methods have been used to quantify the absorption properties of chromophoric or colored dissolved organic matter (CDOM). Different spectroscopic parameters can be used as surrogates of optical properties; furthermore, advanced mathematical tools have also been applied to investigate the absorption spectrum. This study evaluated the most commonly used spectroscopic parameters in remote sensing research and advanced mathematical methods using absorption data on primary biomass constituents (BCs) in aqueous states. We found that, out of the eight spectrometric parameters, the spectral slope in the 275–295 nm range (S275–295) had the strongest correlation with the hydrogen to carbon ratio (H/C), and the spectral slope ratio (275–295 to 350–400 nm) SR and the absorbance ratio between 465 and 665 nm (E4/E6) had a strong correlation with the oxygen to carbon ratio (O/C). Additionally, the spectroscopic parameter values for the solutions of the BCs exhibited distinguishable differences. Gaussian fitting was suitable for single CDOM components but not for complex mixtures. Derivative analysis can be used for single-component discrimination with an extensive investigation of the absorption properties of this component. Additionally, we propose a possible bottom-up perspective to track the origins of CDOM through the absorption spectrum.

Theoretical expressions for the collision-induced absorption spectra of a dipolar and a homonuclear diatomic pair are presented. For the dipolar species, the line strengths and transition frequencies are taken from the HITRAN database, whereas for the homonuclear molecule, the polarizability matrix elements and spectroscopic parameters are obtained from the literature. As specific examples, we consider the double fundamental vibrational transition in CO2−N2, and the H2O−N2 transition in the region of the nitrogen fundamental. For the former pair, the theoretical results are in good agreement with experimental data. For the latter pair, we show that the collision-induced absorption for high humidity conditions is larger than that of N2−N2 pairs above 2500 cm−11, but for lower wavenumbers, it is much weaker than the measured foreign continuum resulting from the far wings of allowed transitions.

Theoretical expressions for the collision-induced absorption spectra of a dipolar and a homonuclear diatomic pair are presented. For the dipolar species, the line strengths and transition frequencies are taken from the HITRAN database, whereas for the homonuclear molecule, the polarizability matrix elements and spectroscopic parameters are obtained from the literature. As specific examples, we consider the double fundamental vibrational transition in CO2−N2, and the H2O−N2 transition in the region of the nitrogen fundamental. For the former pair, the theoretical results are in good agreement with experimental data. For the latter pair, we show that the collision-induced absorption for high humidity conditions is larger than that of N2−N2 pairs above 2500 cm−11, but for lower wavenumbers, it is much weaker than the measured foreign continuum resulting from the far wings of allowed transitions.

The 2024 edition of the HITRAN database represents a major advancement in the curation and dissemination of molecular spectroscopic data. A major aspect of HITRAN2024 is the expansion of line-by-line spectroscopic parameters. This now encompasses 61 molecules and includes “planetary” gases such as S2, CH3 and H3+. These line lists feature improved accuracy and broader spectral coverage compared to HITRAN2020 [1]. Enhancements are especially relevant for interpreting high-resolution observations from state-of-the-art space telescopes such as the James Webb Space Telescope and the Atacama Large Millimeter/submillimeter Array, which require highly accurate spectroscopic data for the remote characterization of planetary atmospheres.The HITRAN2024 update also marks a dramatic expansion in the absorption cross section dataset. Absorption cross sections for over 260 molecules not previously represented in HITRAN have been added to the database, including many from the Pacific Northwest National Laboratory [2]. These additions have been made possible thanks to a wealth of newly available experimental data and extend the range of temperatures, pressures, broadening gases, and spectral resolutions covered.Furthermore, new experimental works have also allowed for an update of the collision-induced absorption data in HITRAN, and the inclusion of new collisional pairs. Additionally, a major new component added to the database in HITRAN2024 is the MT_CKD water vapor continuum model. This complements the existing five core areas of the HITRAN database and the data allows for more accurate simulations of water vapor’s contribution to atmospheric opacity. This update is particularly important in climate modeling and remote sensing applications.The HITRAN2024 edition will be available through the HITRAN website (https://hitran.org) and through the HITRAN Application Programming Interface (HAPI), which supports the expanded dataset. The upcoming publication describing the new edition is in preparation. Overall, HITRAN2024 delivers extensive improvements that reinforce its role as a dependable resource in atmospheric, terrestrial, and astronomical spectroscopic research.

A resynthesis or re-extraction?: Plant Biochemistry and Molecular Biology (2nd edition), edited by Peter J. Lea and Richard C. Leegood

History and future of the molecular spectroscopic databases

Many applications involving atmospheric radiation need radiative transfer codes with an appropriate combination of accuracy, speed, and spectral coverage. In this paper, a new formulation, to our knowledge, of the L-distributions (LD) method is developed for modeling infrared sensor transmittances and radiances in inhomogeneous thermodynamic atmospheres containing a mixture of absorbing gases with variable concentrations. The formulation, called the modified L-distributions (MLD) method, overcomes the limitations of the LD method and establishes a balance between speed and accuracy. The atmosphere is considered a plane-parallel medium, limited at the top by the vacuum, while the kernel bidirectional reflectance distribution function is used to describe the anisotropy of the ground surface. The vertical structure of the plane-parallel atmosphere is subdivided into homogeneous layers of constant or variable discretization steps. It is demonstrated that the transmittance in an inhomogeneous atmosphere using the MLD method requires solving an equivalent homogeneous problem with the absorption coefficient equal to the weighted sum of absorption coefficients of all layers (above or below the observation point) and with thickness equal to the highest discretization step. The weighting factor is the ratio of the layer height to the highest discretization step. Compared to the standard version of the LD method, the MLD formulation is shown to be (1)independent of the direction of propagation along a non-uniform path, (2)more accurate, and (3)more computationally economic and efficient. The line-by-line (LBL) results are used as a benchmark for the comparison of the atmospheric transmittance. Daytime and nighttime top-of-atmosphere (TOA) radiances for a Lambertian ground surface are plotted and compared with the atmospheric radiative transfer code MATISSE outputs. The MLD method results match well with the MATISSE ones. Four locations with anisotropic surface configurations are also studied, and the daytime and nighttime TOA irradiance and albedo are estimated. For the atmospheres studied in this work, the MLD method yields absolute errors less than 1.1% transmittance with a CPU time of 0.2s on an Intel Xeon W1250P 4.10GHz computer. This means that the MLD method is about 2.5 times more accurate and 30 times faster than the standard LD method.

Evaluation of spectroscopic databases through radiative transfer simulations compared to observations. Application to the validation of GEISA 2015 with IASI and TCCON

<p>Since 2016 the Juno spacecraft has been in orbit around Jupiter, gathering unprecedented data from its highly inclined 53-day orbit. The Jupiter Infrared Auroral Mapper (JIRAM) is an imager and spectrograph with spectral coverage between 2 and 5 µm. This region is dominated by reflected sunlight by aerosols and hazes, with distinct absorptions by ammonia, phosphine, germane and other minor species in Jupiter's troposphere, as well as ionospheric H<sub>3</sub><sup>+</sup> at high altitude. Here, we outline the process undertaken to model the full spectral coverage of JIRAM with NEMESIS, our radiative transfer and retrieval code (Irwin et al., 2008). This includes altering the NH<sub>3</sub> aerosol and haze properties, updating the molecular line-list, and testing the sensitivity to the abundance of the molecular species that are within the 2-5 µm range offered by JIRAM. </p> <p>This study builds on previous models for JIRAM spectra in thermal emission (Grassi et al., 2020) and reflected sunlight (Grassi et al., 2021), by attempting to fit the entire 2-5 µm range simultaneously with a single consistent aerosol model.  The model includes two aerosol layers, a NH<sub>4</sub>SH type layer at 1.3 bars, and a NH<sub>3</sub> type layer at 0.7 bars, as well as a tholin type haze layer that extends from the troposphere to the stratosphere. We demonstrate that JIRAM observations of both reflected sunlight and thermal emission cannot be reproduced simultaneously using standard refractive indices available in the literature.  We build a simple model of the refractive indices for the three aerosol layers, adapting the technique of Sromovsky et al. (2010), and demonstrating the improvement in the fits at each step.  As a proof of concept we present the analysis of meridionally averaged zonal profiles, investigating how aerosols, ammonia, and phosphine vary with latitude during the early perijoves of the mission.</p>

Recent improvements in the spectroscopic data for water vapor have significantly increased the near‐infrared absorption in models of the Earth's atmosphere. The climatic effects of increased near‐infrared absorption have been simulated with the latest Community Atmosphere Model (CAM3). The shortwave parameterization in CAM3 has been updated to minimize differences between CAM3 and line‐by‐line (LBL) calculations based upon the High Resolution Transmission (HITRAN) spectroscopic database issued in 2001. The new model reproduces LBL calculations of the near‐infrared absorption to within 0.9% ± 1.4% and the near‐infrared heating rates to within 0.02 ± 0.02 K d−1. Estimates of the global annual mean shortwave absorption by water vapor have been calculated from the editions of the AFGL and HITRAN databases issued in 1982 and 2001, respectively. The main changes in water vapor spectroscopy during this period are the addition of many missing weak lines and increased estimates of line strength in near infrared wavelengths. The clear‐sky and all‐sky shortwave absorption increase by 4.0 W m−2 and 3.1 W m−2, respectively, in calculations replacing the old with the new spectroscopic parameters. The atmosphere becomes warmer, moister, and more stable with the increased absorption in simulations with sea surface temperatures either prescribed from observations or predicted using a slab‐ocean model. The latent heat flux and precipitation both decrease by approximately 2%. Hence the additional absorption has the effect of weakening the hydrological cycle in the atmospheric model.