[en] A high resolution Michelson interferometer has been used to obtain solar spectra from a jet aircraft in the low stratosphere. The spectra are absolutely calibrated in intensity, enabling the solar brightness temperature to be specified from 200 to 700 μ. Concentrations of trace gases in the stratosphere are determined from intensity of absorption lines

[en] High-resolution Fourier-transform IR (FTIR) absorption spectroscopy is presently used over open paths in biomass-fire smoke plumes to remotely sense emissions. FTIR can be employed in simultaneous measurements of a wide range of gas-phase species. Measurements are integrated over a long path through the smoke plume, and are therefore not subject to small-scale local variations. The emissions of all nitrogen species from the four field fires studied can be compared to the nitrogen content of the fuels burned; valuable insight has been gained into the relationships between biomass burning emissions and fire parameters

[en] Recent work on new line parameters for the X¹Σ⁺(0-0),(0-1) H⁷⁹Br, H⁸¹Br bands and the X¹Σ⁺(0-0), (0-1) HI bands, which include hyperfine structure components, has been extended for an update of spectroscopic databases in use for atmospheric spectroscopy. The updated line parameters, now incorporated in HITRAN 2001, are discussed in comparison to HITRAN 1996

[en] The authors have used a Fourier transform spectrometer aboard the NASA DC-8 aircraft during the Airborne Antarctic Ozone Experiment to record infrared absorption spectra of the polar stratosphere. From these high-resolution spectra they derived vertical column amounts above flight altitude of HCl, HF, NO, NO₂, ClCNO₂, and HNO₃ for 10 flights poleward of 60 degree S. Within the polar vortex, where low values of total ozone are observed during the latter part of the observation period, they observed markedly reduced columns of HCl, NO₂, and HNO₃. HCl values in the vortex were in the range of 3-9 x 10¹⁴ molecules/cm², compared with values around 15-20 x 10¹⁴ molecules/cm² in mid-latitudes and ∼30 x 10¹⁴ molecules/cm² in high northern latitudes. The ratio of HCl to HF was also abnormally low, implying that the HCl had been chemically or physically removed, rather than simply being redistributed by atmospheric motion. NO₂ values within the inner vortex were near 5.0 x 10¹⁴ molecules/cm², about a factor of 4 less than columns outside the vortex boundary. HNO₃ values were lower by a factor of 3 within the vortex, compared with a column of approximately 15 x 10¹⁵ molecules/cm² outside the vortex. HNO₃ columns outside the vortex are similar to northern hemisphere values. The ClONO₂ column was relatively large within the vortex, peaking at ∼30 x 10¹⁴ molecules/cm² near the boundary of the vortex. An upper limit of ∼8 x 10¹⁴ molecules/cm² is placed on the column amount of HOCl inside the vortex

[en] A number of prominent Q-branches of the ν₇ band of C₂H₆ have been identified near 3000 cm^-1 in aircraft and ground-based infrared solar absorption spectra. The aircraft spectra provide the column amount above 12 km at various altitudes. The column amount is strongly correlated with tropopause height and can be described by a constant mixing ratio of 0.46 ppbv in the upper troposphere and a mixing ratio scale height of 3.9 km above the tropopause. The ground-based spectra yield a column of 9.0 x 10¹⁵ molecules cm^-2 above 2.1 km; combining these results implies a tropospheric mixing ratio of approximately 0.63 ppbv

[en] This work introduces remote sensing of biomass burning emissions using high-resolution Fourier transform infrared (FTRI) absorption spectroscopy over open paths in smoke plumes from biomass fires. This technique provides an overview of the combustion products from burning not available from any other single technique used to date and can yield much valuable information on the gaseous emission products from biomass burning and the factors which control the balance of those emissions. Using FTIR absorption spectroscopy over long, open paths, the authors have made measurements of the smoke composition from sagebrush and forestry slash fires in rural areas of Wyoming and Montana, and from various fuels in the stack of a large-scale combustion laboratory. In this chapter they report a preliminary analysis of the spectra obtained from the field studies and presnt simultaneous measurements of CO₂, CO, CH₄, CH₂O, NO, NO₂, NH₃, N₂O, and HCN in the plumes of four fires

[en] Hyperfine lines associated with the X¹Σ⁺ (0-0) and (0-1) bands of H¹²⁷I are generated. Discussion of the HI line parameters in the HITRAN and SAO databases is presented. The new (0-0) line parameters are based on previously published far-infrared constants. High-resolution laboratory spectra in the infrared fundamental band region are presented and analyzed for new fine structure spectroscopic constants, which are combined with available hyperfine structure constants for calculating the new (0-1) line parameters. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

[en] The Atmospheric and Environmental Research, Inc., photochemical model has been used to simulate the concentrations and time development of key trace gases in the Antarctic stratosphere before, during, and after the Airborne Antarctic Ozone Experiment (AAOE). The model includes complete gas phase photochemistry and heterogeneous reactions of ClNO₃ (g) and N₂O₅ (g) with HCl (s) and H₂O (s). Observations of long-lived species by the AAOE instruments have been used to constrain the initial conditions in these calculations. The authors present results from four cases illustrating the evolution of the trace gases for a range of possible initial conditions and duration of heterogeneous activity. The amount of ClO produced by heterogeneous conversion of HCl is determined not only by the initial concentrations of NO_x (NO + NO₂ + NO₃),N₂O₅, and ClNO₃ during winter, but also by the rate at which NO_x is resupplied by photolysis of N₂O₅ and HNO₃, or by transport. Results from the four cases presented bracket column measurements of HCl, ClNO₃, and HNO₃ by the Jet Propulsion Laboratory and National Center for Atmospheric Research infrared spectrometers on board the NASA DC-8, and in situ measurements of ClO and NO_y by instruments aboard the NASA ER-2. Comparison of results and measurements of HCl and ClO suggests that heterogeneous chemistry was maintained throughout the month of September in 1987. They suggest field observations and kinetic data which would further constrain the photochemistry of the spring Antarctic stratosphere