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Ab initio calculations of the shapes of pure CO2 infrared and Raman bands under (pressure) conditions for which line-mixing effects are important have been performed using requantized classical molecular dynamics simulations. This approach provides the autocorrelation functions of the dipole vector and isotropic polarizability whose Fourier-Laplace transforms yield the corresponding spectra. For that, the classical equations of dynamics are solved for each molecule among several millions treated as linear rigid rotors and interacting through an anisotropic intermolecular potential. Two of the approximations used in the previous studies have been corrected, allowing the consideration of line-mixing effects without use of any adjusted parameters. The comparisons between calculated and experimental spectra under various conditions of pressure and temperature demonstrate the quality of the theoretical model. This opens promising perspectives for first principle ab initio predictions of line-mixing effects in absorption and scattering spectra of various systems involving linear molecules. [ABSTRACT FROM AUTHOR]

Abstract: In this work, Complex Robert–Bonamy calculations of half-widths and line shifts were done for N2-broadening of water for 1639 transitions in the rotational band using two models for the trajectories. The first is a model correct to second order in time, the Robert–Bonamy parabolic approximation. The second is the solution of Hamilton''s equations. Both models use the isotropic part of the atom–atom potential to determine the trajectories. The present calculations used an intermolecular potential expanded to 20th order to assure the convergence of the half-widths and line shifts. The aim of the study is to assess if the difference in the half-widths and line shifts determined from the two trajectory models is greater than the accuracy requirements of the spectroscopic and remote sensing communities. The results of the calculations are compared with measurements of the half-widths and line shifts. It is shown that the effects of the trajectory model greatly exceed the needs of current remote sensing measurements and that line shape parameters calculated using trajectories determined by solving Hamilton''s equations agree better with measurement. [Copyright &y& Elsevier]

Abstract: In a previous series of papers, a model for the calculation of CO2-air absorption coefficients taking line-mixing into account and the corresponding database/software package were described and widely tested. In this study, we present an update of this package, based on the 2008 version of HITRAN, the latest currently available. The spectroscopic data for the seven most-abundant isotopologues are taken from HITRAN. When the HITRAN data are not complete up to J″=70, the data files are augmented with spectroscopic parameters from the CDSD-296 database and the high-temperature CDSD-1000 if necessary. Previously missing spectroscopic parameters, the air-induced pressure shifts and CO2 line broadening coefficients with H2O, have been added. The quality of this new database is demonstrated by comparisons of calculated absorptions and measurements using CO2 high-pressure laboratory spectra in the 1.5–2.3μm region. The influence of the imperfections and inaccuracies of the spectroscopic parameters from the 2000 version of HITRAN is clearly shown as a big improvement of the residuals is observed by using the new database. The very good agreements between calculated and measured absorption coefficients confirm the necessity of the update presented here and further demonstrate the importance of line-mixing effects, especially for the high pressures investigated here. The application of the updated database/software package to atmospheric spectra should result in an increased accuracy in the retrieval of CO2 atmospheric amounts. This opens improved perspectives for the space-borne detection of carbon dioxide sources and sinks. [ABSTRACT FROM AUTHOR]

Abstract: First measurements of line intensities for ν 1 and ν 3 bands of D2 32S are reported. About 300 intensities of D2 32S vibration–rotation lines were obtained from experimental high-resolution spectra recorded in the 1810–2051cm−1 region with the Fourier Transform Spectrometer built in Reims. Empirical values of transition moment parameters for ν 1 and ν 3 bands of D2 32S were determined for the first time using a least-square fit to the observed intensities. Experimental D2 32S intensities were compared with recent global variational predictions [Vl.G. Tyuterev, L. Régalia-Jarlot, D.W. Schwenke, S.A. Tashkun, Y.G. Borkov, C. R. Phys. 5 (2004) 189–199] computed from isotopically invariant potential and dipole moment functions of the hydrogen sulphide molecule. Average discrepancy between these calculations and our observed data was 0.03cm−1 for line positions of this spectral range. The discrepancy between these calculations and our measurements for the sum of line intensities was 5.5% and 3.5% for the ν 1 and ν 3 bands, correspondingly. [Copyright &y& Elsevier]

Regional processes play a key role in the global carbon budget. Major ocean CO 2 uptake at mid-latitudes counteracts CO 2 release in the tropics, which is modulated by episodes of marine heatwaves. Yet, we lack essential knowledge on persistent marine heatwaves, and their effect on the CO 2 sensitive areas. Here we show, using a 1985-2017 joint analysis of reconstructions, ocean reanalysis and in situ and satellite data, that persistent marine heatwaves occur in major CO 2 uptake and release areas. Average air-sea CO 2 flux density changes from persistent marine heatwaves are strongest in the Pacific Ocean with a 40 ± 9% reduction in CO 2 release in the tropics linked to ENSO, and a reduction in CO 2 uptake of 29 ± 11% in the North Pacific over the study period. These results provide new insights into the interplay of extreme variability and a critical regulating ocean ecosystem service, and pave the way for future investigations on its evolution under climate change., (© 2022. The Author(s).)