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.

Calibrated 0.1-cm(-1) IR emission spectra from 80°N.

Spectra from a 0.1-cm(-1) resolution absolutely calibrated emission interferometer installed near Eureka, Northwest Territories, Canada (80°N, 86°W), at the Arctic Stratospheric Observatory are presented. The Michelson-type interferometer has a maximum path difference of 10 cm and uses a liquid-N(2)-cooled HgCdTe detector, which covers the spectral region from 650 to 1250 cm(-1). Spectral intervals containing CO(2), HNO(3), and ozone have been modeled with a line-by-line radiative-transfer code and column amounts retrieved for the latter two constituents. The instrument and initial measurements are described.

University of Denver infrared spectral atlases.

Atmospheric and laboratory atlases of high-resolution infrared absorption spectra have been generated from data obtained with the University of Denver Michelson-type interferometer balloon-borne spectrometer systems. The main objectives of the atlas work have been the identification and the detailed analysis of stratospheric infrared high-resolution spectral features. The stratospheric atlases cover many spectral intervals and provide tables of line positions and species identifications. High Sun spectra are used for identification of solar lines. Latest editions of these atlases include selected sections in the 760-1950- and 800-1700-cm(-1) regions at 0.02- and 0.002-cm(-1) resolutions, respectively. In addition to the stratospheric atlases, ground-based and laboratory spectral atlases have also been produced. The laboratory spectra of many molecules relevant to stratospheric chemistry have been obtained. A number of ongoing spectroscopic studies have been developed on the basis of the atlas work, including studies of solar and atmospheric spectral features.

High resolution solar spectrometer system for measuring atmospheric constituents.

A mid IR Michelson interferometer capable of obtaining 0.002-cm(-1) resolution solar spectra has been developed for balloon use. The interferometer is based on the Bomem self-aligning instrument, and is equipped with a solar tracking system, telemetry, and recording systems, as well as temperature control and gondola orientation. The interferometer has made two successful flights in the 7-14 microm (700-1300-cm(-1)) interval up to 40 km. The basic systems are described and sample spectra are presented.

Infrared measurements of increased CF(2)Cl(2) (CFC- 12) absorption above the South Pole.

High-resolution ground-based solar spectra recorded at the Amundsen-Scott South Pole station in Dec. 1980 and Nov. 1986 have been analyzed in the region of the CF(2)Cl(2) (chlorofluorocarbon 12) nu(8) band Q branches at 1161 cm(-1). An increase in the CF(2)Cl(2) total vertical column above the South Pole of 1.24 +/- 0.15 over the 6-yr period, corresponding to an average rate of increase of 3.6 +/- 2.1%, is derived. This rate of increase is lower than indicated by in situ measurements at the South Pole over the same time period, but there is agreement when the rather error bars of the spectral measurement results are considered. Spectroscopic parameters that can successfully model CF(2)C1(2) absorption at low temperatures are needed to improve retrieval accuracies and could be applied to a number of pre-1980 atmospheric spectral data sets in the literature to obtain an improved record of early CF(2)Cl(2) concentration trends for comparison with estimates of historical release rates.

Stratospheric N(2)O mixing ratio profile from high-resolution balloon-borne solar absorption spectra and laboratory spectra near 1880 cm(-1).

A nonlinear least-squares fitting procedure has been used to derive the stratospheric N(2)O mixing ratio profile from balloon-borne solar absorption spectra and laboratory spectra near 1880 cm(-1). The atmospheric spectra were recorded during sunset from a float altitude of 33 km with the University of Denver 0.02-cm(-1) resolution interferometer near Alamogordo, N.M. (33 degrees N), on 10 Oct. 1979. The laboratory data were used to determine the N(2)O line intensities. The measurements indicate an N(2)O mixing ratio of 264 ppbv near 15 km decreasing to 155 ppbv near 28 km.

Changes in stratospheric water vapor associated with the mount st. Helens eruption.

A frost point hygrometer designed for aircraft operation was included in the complement of instruments assembled for the NASA U-2 flights through the plume of Mount St. Helens. Measurements made on the 22 May flight showed the water vapor to be closely associated with the aerosol plume. The water vapor mixing ratio by mass in the plume was as high as 40 x 10(-6). This compares with values of 2 x 10(-6) to 3 x 10(-6) outside of the plume.

Astronomical monochromatic imaging as applied to the lo sodium cloud.

We compare four types of instruments for recording monochromatic astronomical images: filters; slitless spectrographs; multislit spectrographs; and interferometers. Each of these instruments has been used on the sodium emission cloud of o, with varying degrees of success. Multislit spectrographs and interferometers encode the signal, and it can be extracted with a noise level close to that for photon statistics. This is not normally the case for filters and slitless spectrographs. On balance, we find that a Mach-Zehnder interferometer provides the best system for imaging faint monochromatic signals on a brighter continuum background.