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ABSTRACT: The Smithsonian far-infrared spectrometer is a remote sensing Fourier transform spectrometer that measures the mid- and far-infrared thermal emission spectrum of the stratosphere from balloon and aircraft platforms. The spectrometer has had nine successful balloon flights from 1987 to 1994, flying at float altitudes of 36--39 km and collecting 131 hours of midlatitude stratospheric limb spectra. The spectrometer also flew on a NASA DC-8 aircraft, as part of the second Airborne Arctic Stratospheric Expedition (AASE-II), collecting 140 hours of overhead spectra at latitudes ranging from the equator to the north pole. We present here a brief description of the instrument, a discussion of data reduction procedures, an estimation of both random and systematic errors, an outline of the procedure for retrieving mixing ratio profiles, and an explanation of the method of deriving temperature and pressure from the far- and mid-infrared spectra. 1. Introduction The far-infrared spectrometer (F...
04/1999;
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ABSTRACT: Balloon-borne observations of concentrations of OH, HO2, H20, and O3 in the middle and upper strato-sphere are used to test our understanding of HOx photo-chemistry. Assuming our photochemical model is complete, the measured [OH] and [HO2] above 38 km (where HOx par-titioning is no longer dependent on [NO]) are modeled best by calculations that use a 25% reduction in the ratio of the reaction rate constants for O+HO2 and O+OH as well as either a 25% reduction of the rate constant of OH+HO2 (the primary HO • sink) or a 25% increase in HO • production. All of these changes are consistent with the uncertainties in the recommended rate constants. The kinetic parameters required to explain our observations of [OH] and [HO • ] do not lead to a resolution of the long-standing "ozone deficit problem" above 45 kin.
01/1998; 25(1):3935-3938.
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ABSTRACT: The research performed during this reporting period includes spectroscopic studies to determine molecular parameters from OH, HO2, H2O2, H2O, O3, and HI. We have now developed an expertise in ultra-high resolution spectroscopy using the TuFIR method that includes: the development of radical source chemistries, allowing us to measure pressure broadening and line positions of OH, HO2 and ClO; development of 3-wave mixing, which trades off some of the power available in the tunable far infrared beam for much wider tunability -- for a particular measurement, either 2-wave or 3-wave mixing can be chosen according to experimental need; design and fabrication of spectroscopy cells, a flow-metering system for radical chemistry, and other laboratory apparatus; development of instrument control and data acquisition software, allowing for precise control of the TuFIR instrument parameters and long integration times for weak spectral lines; development of software for nonlinear least-squares fitting of measured spectra to obtain pressure broadening coefficients and/or line positions, based upon the algorithm of Marquardt; development of software to perform multiple linear regressions to obtained line broadening and/or shifting information from studies employing complex source chemistries; and development of Hamiltonian fitting capability that includes asymmetric top molecules with centrifugal distortion up to optic, with electron spin, nuclear spin, and nuclear quadrupole interactions.
06/1996;
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ABSTRACT: The first simultaneous measurements of HO(x), NO(x), and Cl(x) radicals in the middle stratosphere show that NO(x) catalytic cycles dominate loss of ozone (O3) for altitudes between 24 and 38 km; Cl(x) catalytic cycles are measured to be less effective than previously expected; and there is no 'ozone deficit' in the photochemically dominated altitude range from 31 and 38 km, contrary to some previous theoretical studies.
02/1996;
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ABSTRACT: Combined infrared and microwave remote sensing measurements of the
stratosphere are combined to test several aspects of a constrained
photochemical model. The authors find that a model with conventional
chemistry only is unable to reproduce the observed abundance of ClO and
HOCl relative to HCl, while results from a model which includes 10%
production of HCl from the reaction of OH and ClO are in good agreement
with the observations. The modified model predicts that the rates of
production and loss of ozone are in balance at altitudes where the
photochemical lifetimes are short compared to the characteristic
transport time (30-40 km), in agreement with the rates calculated
directly from the authors' measurements of HO<sub>2</sub>, OH, NO<sub>2
</sub>, O<sub>3</sub>, and ClO. The modified model also shows that for
the balloon flight analyzed halogen-catalyzed ozone loss plays a lesser
role than previously believed
Combined Optical-Microwave Earth and Atmosphere Sensing, 1995. Conference Proceedings., Second Topical Symposium on; 05/1995
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ABSTRACT: This report covers the time period 1 Jul. to 31 Dec. 1993. There were no balloon or airplane flights during this reporting period, instead the authors concentrated on analyzing existing data. This was facilitated by a recently completed program of enhancements made in data reduction software. They are using their data sets to examine the changes in stratospheric chemistry over a variety of time scales. Ongoing projects include investigating the diurnal variation of OH, HO2, and H2O2 and exploring their relationships with other simultaneously measured species; measuring long term trends in HF and HCl; and looking for changes caused by the June 1991 Pinatubo eruption. They are also continuing to analyze the large set of data collected during the AASE 2.
12/1993;
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ABSTRACT: This report covers the time period 1 January 1993 to 30 June 1993. During this reporting period the authors had their third Upper Atmosphere Research Satellite (UARS) correlative balloon flight and submitted the results from this flight to the Central Data Handling Facility (CDHF). They made a number of improvements in their data processing software in preparation for a new analysis of their old balloon data sets. Finally, they continue to analyze the data obtained during the second Airborne Arctic Stratospheric Expedition (AASE 2).
07/1993;
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ABSTRACT: An upper limit is measured for stratospheric HBr from three balloon flights. The observations were made with the FIRS-2 far-infrared Fourier transform spectrometer. The 1sigma upper limits from the 1988, 1989, and 1990 balloon flights are 13 pptv at 35 km, 7 pptv at 32 km, and 3 pptv at 31 km, respectively. Combining all 3 flights, the weighted average 1sigma upper limit for HBr is 4 pptv at 32 km. This value is significantly smaller than the only other previously published spectroscopic value of 20 +/- 7 pptv (2sigma), but is consistent with a theoretical estimate which predicts roughly 0.4 pptv at this altitude.
09/1992;
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ABSTRACT: The first unequivocal measurement of hydrogen peroxide in the stratosphere have been made, a concentration profile obtained from a balloon platform using Fourier transform thermal emission spectroscopy in the far infrared. Measurements were made using the 112/cm R-Q5 branch of the rotational-torsional spectrum, with some confirmation from the 94/cm R-Q4 branch. The volume mixing ratio of H2O2 is 1.6 x 10 to the -10th at 38.4 km, decreasing to 0.6 x 10 to the -10th at 23.8 km, with uncertainties of about 16 percent. These measurements are compared to a recent stratospheric model calculation.
07/1991;
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ABSTRACT: The magnetic dipole-allowed spin-rotation lines of O2 potentially can be used for pointing calibration and confirmation of float altitude for far infrared spectra of the stratosphere obtained from balloon platforms. We demonstrate that current deficiencies in the spectroscopic database, particularly the air pressure-broadening coefficients, severely limit the capability of deriving useful pointing calibrations, and that precise pressure-broadening measurements for the transitions actually used in calibration are needed to improve this capability.
International Journal of Infrared and Millimeter Waves 05/1991; 12(6):581-588. · 0.58 Impact Factor
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ABSTRACT: Tunable far-infrared spectroscopy was used to measure pressure broadening of the 118.455/cm rotational lines of OH by H2, He, N2, and O2. Broadening coefficients of H2 and He were measured for the temperature range of 296 to 80 K, and N2 and O2 broadening coefficients were measured for the 296-210 K temperature range.
02/1991;
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ABSTRACT: The pressure broadening coefficients of the 2.5 THz rotation line of H(Cl-35) by N2 and O2, for application to the analysis of far infrared spectra obtained in the stratosphere, are reported. The broadening coefficients were measured in absorption at 296 and 201 L using a tunable far infrared spectrometer. Results show that at room temperature the N2 pressure broadening coefficient is 0.0669 +/-0.0021/cm/atm (2sigma), with a temperature coefficient B of 0.58 +/-0.02.
02/1991;
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ABSTRACT: Observations of the vertical profile of hydrogen fluoride (HF) vapor in the stratosphere and of the vertical column amounts of HF above certain altitudes were made using a variety of spectroscopic instruments in the 1982 and 1983 Balloon Intercomparison Campaigns. Both emission instruments working in the far-infrared spectral region and absorption instruments using solar occultation in the 2.5-micron region were employed. No systematic differences were seen in results from the two spectral regions. A mean profile from 20 - 45 km is presented, with uncertainties ranging from 20 to 50 percent. Total columns measured from ground and from 12 km are consistent with the profile if the mixing ratio for HF is small in the troposphere and low stratosphere.
03/1990;
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William G. Mankin,
M. T. Coffey, K. V. Chance,
W. A. Traub,
B. Carli,
F. Mencaraglia,
S. Piccioli,
I. G. Nolt,
J. V. Radostitz,
R. Zander,
G. Roland,
Douglas W. Johnson,
Gerald M. Stokes,
C. B. Farmer,
R. K. Seals
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ABSTRACT: Observations of the vertical profile of hydrogen fluoride (HF) vapor in the stratosphere and of the vertical column amounts of HF above certain altitudes were made using a variety of spectroscopic instruments in the 1982 and 1983 Balloon Intercomparison Campaigns. Both emission instruments working in the far infrared spectral region and absorption instruments using solar occultation in the 2.5m region were employed. No systematic differences were seen in results from the two spectral regions. A mean profile from 20–45 km is presented, with uncertainties ranging from 20% to 50%. Total columns measured from ground and from 12 km are consistent with the profile if the mixing ratio for HF is small in the tropophere and low stratosphere.
Journal of Atmospheric Chemistry 01/1990; 10(2):219-236. · 0.99 Impact Factor
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ABSTRACT: Determinations have been made of concentration profiles of HOCl in the earth's stratosphere, including the diurnal variation. Measurements of the rotational Q2 branch at 99.5/cm and of five RR(J3) transitions between 143 and 159/cm were made using far-infrared thermal emission spectroscopy. The spectra were obtained during a balloon flight of the FIRS 2 far-infrared Fourier-transform spectrometer and telescope from Palestine, Texas on May 12-13, 1988. From these measurements, altitude profiles of HOCl from 23 to 42 km are obtained. Daytime and nighttime average profiles of HOCl, as well as measurements on a 30-min time scale through the sunset transition at a single (35 km) altitude are presented. The measured profiles are lower than the current predictions from several modeling groups by a factor of approximately 0.6.
09/1989;
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ABSTRACT: A statistically significant measurement of H2O2 in the stratosphere has been obtained. The results were obtained from the 112.19/cm RQ5 branch of the torsional-rotational spectrum with a remote-sensing far-infrared Fourier transform spectrometer during the Balloon Intercomparison Campaign (BIC-2), on June 20, 1983. The concentration above the balloon gondola is unexpectedly large, corresponding to 0.68 + or - 0.21 parts per billion by volume (ppbv) at an effective altitude of 38.3 km. Below the gondola altitude the concentration of H2O2 is slightly less than expected from the model predictions at 33.2 km (0.19 + or - 0.05 ppbv) and significantly less than expected at 29.3 km (0.08 + or - 0.03 ppbv).
04/1987;
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ABSTRACT: The highlights of the stratospheric program were reviewed for the past 2.5 years. The major efforts were analysis of the data from the BIC-2 campaign, and the building or new instrumentation to replace that lost at the end of BIC-2. For clarity, the review will be done by topic, rather than chronologically: construction of the initial far-infrared spectrometer, balloon slight program, laboratory measurement, data analysis, and duplicate stabilized platform.
12/1986;
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ABSTRACT: The balloon flight performance of the Mark I single‐axis platform and telescope is presented. Three performance indicators are examined: inclinometer output, gyro output, and infrared detector signal. We find that the gondola itself experiences periodic angular disturbances with maximum amplitudes in the 0.1°–2.0° range, with peaks occurring at periods of about 1, 2, 7, 20, and 250 s. The 2‐ and 20‐s oscillations are identified with simple and compound pendulum motions, while the 250‐s oscillations are speculated to be caused by atmospheric waves. Maximum platform deviations from the horizontal are in the 0.002°–0.02° range, well within the 0.02° design goal, except in the 250‐s regime where amplitudes are occasionally several times larger than the design goal because of horizontal atmospheric accelerations. We find that the system meets our basic goal of providing a stable pointing direction within an uncertainty which is much less than the 0.3° telescope beam diameter.
Review of Scientific Instruments 11/1986; · 1.37 Impact Factor
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ABSTRACT: We describe the design of two telescope pointing systems for remote optical sensing of the stratosphere from a balloon‐borne gondola. The telescope pointing accuracy is ±0.02° in elevation, from a gondola which has static and dynamic tilts up to ±3°. Each system consists of a telescope, an elevation control subsystem, and a pitch‐stabilized single‐axis reference platform. The Mark I unit has performed successfully on each of its two balloon flights, for a total of over 16 h in the stratosphere; the Mark II unit is currently under construction. The single‐axis platform is referenced to a rate‐integrating gyroscope and an inclinometer for high‐ and low‐frequency pitch‐angle variations, respectively. The Mark I platform is supported by ball bearings, driven by a brush‐contact torque motor, and is subject to a small, permanent pitch angle error which depends directly on the gyro drift rate. The Mark II platform uses flex‐pivot supports, a brushless motor, and for even a relatively large gyro drift rate, is designed to asymptotically approach zero angular offset error.
Review of Scientific Instruments 11/1986; · 1.37 Impact Factor
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ABSTRACT: This paper discusses the spectrum of the earth's stratosphere in the far-infrared, from 5 to 250/cm. Many of the trace gases that are important in stratospheric photochemistry have been measured, or are potentially measurable in the far-infrared. The spectral features of these gases are discussed with application to spacecraft measurements. In particular, the suitability of the spectrum for measurements of the HO(x) and ClO(x) families and of O3 are compared for different classes of instruments: Fourier transform spectrometers, filter radiometers, and scanning high-resolution Fabry-Perot instruments. It is found that these types of instruments have complementary capabilities that would best be used in combination in a comprehensive multispecies measurement scheme.
11/1985;
