Measurements of Lorentz air-broadening coefficients and relative intensities in the H(2)(16)O pure rotational and v(2) bands from long horizontal path atmospheric spectra

An intercomparison of measured pressure-broadening and pressure-shifting parameters of water vapor

The present work is an intercomparison of experimental results on the pressure broadening and pressure shifting of water vapor absorption lines. The work focuses on application to the Earth's atmosphere; hence measurements of nitrogen, oxygen, air, and H2O as the buffer, or perturbing gas, were considered. The literature was searched and over 100 papers found. The data, measured half-widths, their temperature dependence, and the line shifts, were taken and databases created for each perturbing gas. The databases were reordered, grouping data for rovibrational transitions, and intercomparisons of the measurements made. Trends in the data, relationships between the data sets, and dependences on temperature and quantum numbers were investigated. The data were averaged and an estimated uncertainty determined. The averaged data sets are evaluated with respect to the need of the spectroscopic and remote sensing communities. Based on these studies, recommendations for new measurements are made.Key words: water vapor, half-widths, line shifts, temperature dependence of half-width.

Air- and N(2)-Broadening Parameters of Water Vapor: 604 to 2271 cm(-1)

High-resolution measurements of air- and N(2)-broadened widths and pressure-induced frequency shifts of water vapor were obtained covering the spectral region between 604 and 2271 cm(-1). Over 1300 vibration-rotation transitions were measured including the (000)-(000), (010)-(010), (010)-(000), (020)-(010), and (100)-(010) vibrational bands of H(2)(16)O. Also included were measurements of H(2)(18)O and H(2)(17)O from normal water vapor samples and H(2)(18)O + N(2) observations with oxygen-18-enriched gas samples. Collision-narrowing effects were observed in a few lines involving high J and low K(a) transitions with the lowest measured linewidth coefficient equal to 0.0057(4) cm(-1)/atm (air-broadening) for the completely overlapping transitions, 17 0 17 <-- 18 1 18 and 17 1 17 <-- 18 0 18, at 1235.204 cm(-1). The majority of the linewidth values were derived from the measurements using a Voigt line profile. A few lines with air- or N(2)-broadened half-width values of about 0.012 cm(-1) or less were found to exhibit collision-narrowing effects and were also analyzed with a profile proposed by Galatry. The results are compared to values given in previous studies. Copyright 2000 Academic Press.

Observation of pure rotational absorption spectra in the nu2 band of hot H(2)O in flames

We present measurements of absorption spectra of hot-water vapor generated in a propane-air flame in the far-infrared region of the spectrum from 0.1 to 3.5 THz (3.3 to 117cm(-1)). Transitions within the rotational manifold of both the ground and the nu(2)=1 vibrational levels were observed. The measurements are in good agreement with calculations of the predicted absorption spectra at 1300 K based on tabulated line intensities, whereas predicted theoretical line widths were found to be approximately one third too narrow.

Remote sensing of the Earth's atmosphere from space with high-resolution Fourier-transform spectroscopy: development and methodology of data processing for the Atmospheric Trace Molecule Spectroscopy experiment

The methodology of spectroscopic remote sensing with high-resolution Fourier-transform spectra obtained from low Earth orbit by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment is discussed. During the course of the Atmospheric Laboratory for Applications and Science (ATLAS) shuttle missions (1992-1994) a flexible, yet reproducible, retrieval strategy was developed that culminated in the near-real-time processing of telemetry data into vertical profiles of atmospheric composition during the ATLAS-3 mission. The development, evolution, robustness, and validation of the measurements are presented and assessed with a summary comparison of trace-gas observations within the Antarctic polar vortex in November 1994.

1995 Atmospheric Trace Molecule Spectroscopy (ATMOS) linelist

The Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment uses a Fourier-transform spectrometer on board the Space Shuttle to record infrared solar occultation spectra of the atmosphere at 0.01-cm(-1) resolution. The current version of the molecular spectroscopic database used for the analysis of the data obtained during three Space Shuttle missions between 1992 and 1994 is described. It is an extension of the effort first described by Brown et al. [Appl. Opt. 26, 5154 (1987)] to maintain an up-to-date database for the ATMOS experiment. The three-part ATMOS compilation contains line parameters of 49 molecular species between 0 and 10000 cm(-1). The main list, with nearly 700,000 entries, is an updated version of the HITRAN 1992 database. The second compilation contains supplemental line parameters, and the third set consists of absorption cross sections to represent the unresolvable features of heavy molecules. The differences between the ATMOS database and other public compilations are discussed.

Mid-infrared measurements of the atmospheric emission over the South Pole using a radiometrically calibrated Fourier transform spectrometer

We conducted year-round measurements of the downwelling atmospheric infrared emission over the South Pole in 1992. The instrument covered the 550-1600-wave-number region with 1-wave-number resolution. We calculated the water vapor content for clear-sky cases and found a good correlation with the surface temperature, with values ranging from 0.2 to 0.8 mm. Ozone-sonde profiles were compared with total column abundances of O(3) retrieved from the spectra. The experiment is explained in detail, including the instrumentation, calibration, and retrieval methods used. The calibrated spectra contain information about several trace gases, water, clouds, temperature profiles, and aerosols.