The HITRAN2020 molecular spectroscopic database

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

MIPAS ground processor and data products

As an ESA-provided payload instrument on board ENVISAT the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) will routinely acquire atmospheric limb emission spectra in the middle infrared region. Due to its high radiometric sensitivity and spectral resolution capabilities a large number of middle atmospheric constituents can be detected that are of primary interest in the various disciplines of atmospheric research. The ENVISAT ground segment concept foresees generation and near real time dissemination of MIPAS data products up to the level of pressure (p), temperature (T) and volume-mixing ratio (VMR) profiles for the high priority target species O3, H2O, CH4, N2O, HNO3. The basic algorithms have been defined and are currently being verified in various ESA supported studies. End-to-end tests based on simulated instrument raw data have been carried out, using prototype versions of the Level 1 B (processing from raw data up to calibrated radiance spectra) and Level 2 algorithm components (retrieval of vertical p, T and VMR profiles). Runtime checks have been performed for the critical profile retrieval modules. For a reference scenario (p, T plus five trace gas retrievals for a single, 16 heights elevation sequence; one iteration per retrieval), a total runtime of approx. 150 s has been achieved on an IBM RS/6000 model 397

Optimized spectral microwindows for data analysis of the Michelson Interferometer for Passive Atmospheric Sounding on the Environmental Satellite.

For data analysis of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) atmospheric limb emission spectroscopic experiment on Environmental Satellite microwindows, i.e., small spectral regions for data analysis, have been defined and optimized. A novel optimization scheme has been developed for this purpose that adjusts microwindow boundaries such that the total retrieval error with respect to measurement noise, parameter uncertainties, and systematic errors is minimized. Dedicated databases that contain optimized microwindows for retrieval of vertical profiles of pressure and temperature, H2O, O3, HNO3, CH4, N2O, and NO2 have been generated. Furthermore, a tool for optimal selection of subsets of predefined microwindows for specific retrieval situations has been provided. This tool can be used further for estimating total retrieval errors for a selected microwindow subset. It has been shown by use of this tool that an altitude-dependent definition of microwindows is superior to an altitude-independent definition. For computational efficiency a dedicated microwindow-related list of spectral lines has been defined that contains only those spectral lines that are of relevance for MIPAS limb sounding observations

First results of MIPAS/ENVISAT with operational Level 2 code

Michelson interferometer for passive atmospheric sounding (MIPAS) is operating on board of the ENVISAT satellite and is acquiring for the first time high spectral resolution middle infrared emission limb sounding spectra of the Earth atmosphere from space. An optimized code was developed for the Level 2 near real time analysis of MIPAS data. The code is designed to provide, in an automated and continuous way, atmospheric vertical profiles of temperature, pressure and concentrations of O-3, H2O, CH4, HNO3, N2O and NO2, in the altitude range from 12 to 68 km. The performances of the code are herewith derived from the analysis of the first measurements acquired with this instrument. The assumptions made for the development of the optimized code are verified with the real data. The diagnostics of the instrument performances provide indications that there is good agreements with the results obtained by the Level 1 analysis. Consistent geophysical data are retrieved which is a first step towards a more complete assessment of retrieval accuracy. The tests have identified the possibility of measurement improvements by way of some secondary operations such as a correction of the frequency scale and the use of cloud filtering. However, no change in the algorithm baseline appears to be necessary. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved

MIPAS: an instrument for atmospheric and climate research

MIPAS, the Michelson Interferometer for Passive Atmospheric Sounding, is a mid-infrared emission spectrometer which is part of the core payload of ENVISAT. It is a limb sounder, i.e. it scans across the horizon detecting atmospheric spectral radiances which are inverted to vertical temperature, trace species and cloud distributions. These data can be used for scientific investigations in various research fields including dynamics and chemistry in the altitude region between upper troposphere and lower thermosphere. <br><br> The instrument is a well calibrated and characterized Fourier transform spectrometer which is able to detect many trace constituents simultaneously. The different concepts of retrieval methods are described including multi-target and two-dimensional retrievals. Operationally generated data sets consist of temperature, H<sub>2</sub>O, O<sub>3</sub>, CH<sub>4</sub>, N<sub>2</sub>O, HNO<sub>3</sub>, and NO<sub>2</sub> profiles. Measurement errors are investigated in detail and random and systematic errors are specified. The results are validated by independent instrumentation which has been operated at ground stations or aboard balloon gondolas and aircraft. Intercomparisons of MIPAS measurements with other satellite data have been carried out, too. As a result, it has been proven that the MIPAS data are of good quality. <br><br> MIPAS can be operated in different measurement modes in order to optimize the scientific output. Due to the wealth of information in the MIPAS spectra, many scientific results have already been published. They include intercomparisons of temperature distributions with ECMWF data, the derivation of the whole NO<sub>y</sub> family, the study of atmospheric processes during the Antarctic vortex split in September~2002, the determination of properties of Polar Stratospheric Clouds, the downward transport of NO<sub>x</sub> in the middle atmosphere, the stratosphere-troposphere exchange, the influence of solar variability on the middle atmosphere, and the observation of Non-LTE effects in the mesosphere

The 1997 spectroscopic GEISA databank

The current version GEISA-97 of the computer-accessible database system GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques: Management and Study of Atmospheric Spectroscopic Information) is described. This catalogue contains 1,346,266 entries. These are spectroscopic parameters required to describe adequately the individual spectral lines belonging to 42 molecules (96 isotopic species) and located between 0 and 22,656 cm-1. The featured molecules are of interest in studies of the terrestrial as well as the other planetary atmospheres, especially those of the Giant Planets. GEISA-97 contains also a catalog of absorption cross-sections of molecules such as chlorofluorocarbons which exhibit unresolvable spectra. The modifications and improvements made to the earlier edition (GEISA-92) and the data management software are described. GEISA-97 and the associated management software are accessible from the ARA/LMD (Laboratoire de Météorologie Dynamique du CNRS, France) web site: http://ara01.polytechnique.fr/registration