C. B. Farmer

California Institute of Technology, Pasadena, CA, United States

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Publications (83)234.71 Total impact

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    ABSTRACT: The solar spectrum offered the opportunity to discover OH lines with high rotational quantum numbers, which do not appear on laboratory spectra. On solar absorption spectra, we have identified about 580 lines, among which about 400 were observed for the first time. They belong to pure rotational transitions in the ground state (v= 0 → 3;[formula]= 48.5), as well as to the (1–0), (2–1), and (3–2) vibration–rotation bands[formula]= 32.5). Previous pure rotation, vibration–rotation, and Λ-doubling data sets related to thev= 0 up to 3 levels were fitted simultaneously together with this new set of data, in order to obtain a very complete and accurate set of molecular constants for theX2Π ground state.
    Journal of Molecular Spectroscopy 12/1995; 174(2):490–509. · 1.67 Impact Factor
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    ABSTRACT: A simple, classical, and expedient method for the retrieval of atmospheric pressure-temperature profiles has been applied to the high-resolution infrared solar absorption spectra obtained with the atmospheric trace molecule spectroscopy (ATMOS) instrument. The basis for this method is a rotational analysis of retrieved apparent abundances from CO2 rovibrational absorption lines, employing existing constituent concentration retrieval software used in the analysis of data returned by ATMOS. Pressure-temperature profiles derived from spectra acquired during the ATLAS 1 space shuttle mission of March-April 1992 are quantitatively evaluated and compared with climatological and meteorological data as a means of assessing the validity of this approach.
    Journal of Geophysical Research 03/1995; · 3.17 Impact Factor
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    01/1995; 81:39.
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    ABSTRACT: Volume mixing ratio profiles of COF2 have been derived through most of the stratosphere between 30 deg N and 54 deg S from series of 0.01-cm(exp -1) resolution infrared solar spectra recorded in the occultation mode by the atmospheric trace molecule spectroscopy (ATMOS) instrument during the ATLAS 1 space shuttle mission of March-April 1992. When compared with similar results obtained from the ATMOS/Spacelab 3 mission of April-May 1985, the cumulative increase in the burden of COF2 in the middle and upper stratosphere was found to be 67% for that 7-year time interval. By combining a subset of these COF2 results with upper stratospheric concentrations of HF also derived from the ATMOS observations, it was further found that the budget of inorganic fluorine above 35 km altitude increased by (60 +/- 10) % over the 1985-1992 time interval, which corresponds to an average exponential rate of increase of(6.7 +/- 1.1) % /yr , or a linear rate of increase referenced to 1985 of (8.5 +/- 1.3) % /yr at the 1(sigma) confidence level. The total inorganic F atom volume mixing ratio found in the upper stratosphere for 1985 and 1992 and the increase during this period mirror the rise in man-made fluorine-bearing compounds at the ground during the early to mid 1980s. This demonstrates the negligible impact of natural sources of fluorine, in particular volcanic activity, on the observed change of F in the upper stratosphere. Implications of the present findings and comparison with model results are discussed.
    Journal of Geophysical Research 09/1994; · 3.17 Impact Factor
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    ABSTRACT: The combined laboratory and solar analysis of the highly-excited subconfigurations 4f and 5g of Fe I has allowed us to classify 87 lines of the 4f-5g supermultiplet in the spectral region 2545-2585 cm-1. The level structure of these JK-coupled configurations is predicted by semiempirical calculations and the quadrupolic approximation. Semiempirical gf-values have been calculated and are compared to gf values derived from the solar spectrum. The solar analysis has shown that these lines, which should be much less sensitive than lower excitation lines to departures from LTE and to temperature uncertainties, lead to a solar abundance of iron which is consistent with the meteoritic value (A_Fe = 7.51). Comment: ApJ (in press). 14 pages. LaTeX AAS macros. 6 figures on request from gill@ferrum.fysik.lu.se. LUND-GN-94-1
    The Astrophysical Journal 04/1994; · 6.73 Impact Factor
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    ABSTRACT: The paper demonstrates the high accuracy of line positions derived from improved sets of Dunham coefficients for the four more abundant isotopic species of carbon monoxide - (C-12)(O-16), (C-13)(O-16), (C-12)(O-18), and (C-12)(O-17) - which are present in the sun and in cool stellar atmospheres. These new spectroscopic constants make it possible to predict very accurate positions of CO lines at any J-values, especially at very high rotational excitation (up to J around 135). Earlier proposed identifications of CO lines at large J-values are checked, and some incorrect identifications in sunspot spectra are found. The present accurate line positions are also compared with predictions from other available sets of molecular constants. It is concluded that the present improved sets of molecular constants are the most appropriate to all problems of high-resolution stellar and solar spectroscopy at any J- and v-values, particularly for synthetic spectra of cool stars.
    12/1992;
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    ABSTRACT: Results are presented of an investigation of the Cl and F inventories derived from the concentrations of eleven Cl- and F-bearing organic and inorganic species throughout the atmosphere, based on observations with the Atmospheric Trace Molecule Spectroscopy instrument aboard the Space Shuttle during the Spacelab 3 mission of April 29 to May 6, 1985. It was found that, in April-May 1985, near 30 deg N, the mean total stratospheric concentrations of Cl and F were 2.58 +/-0.10 ppbv and 1.15 +/-0.12 ppbv, respectively. Partitioning among the source, sink, and reservoir species was consistent with the conservation of the F and Cl budgets throughout the stratosphere. It is shown that the budgets of Cl and F above about 45 km altitude can be determined accurately by measuring only HCl, HF, and CF4 and provide a straightforward timely reference point for future inventories and trends evaluations.
    Journal of Atmospheric Chemistry 09/1992; · 1.33 Impact Factor
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    ABSTRACT: The paper reports simultaneous measurements of the stratospheric burdens of H2O, HDO, OCS, CO2, O3, N2O, CO, CH4, CF2Cl2, CFCl3, CHF2Cl, C2H6, HCN, NO, NO2, HNO3, ClNO3, HOCl, HCl, and HF made by the JPL MkIV interferometer on board the NASA DC-8 aircraft during January and early February 1989 as part of the Airborne Arctic Stratosphere Experiment. Data were obtained on 11 flights at altitudes of up to 12 km over a geographic region covering the NE Atlantic Ocean, Iceland, and Greenland. Analyses of the chemically active gases reveal highly perturbed conditions within the vortex. The ClNO3 abundance was chemically enhanced near the edge of the vortex but was then depleted inside. NO2 was severely depleted inside the vortex. In contrast to Antarctica, H2O and HNO3 were both more abundant inside the vortex than outside. It is suggested that although the Arctic vortex did not get cold enough to produce any dehydration, or as vertically extensive denitrification as occurred in Antarctica, nevertheless, enough heterogeneous chemistry occurred to convert over 90 percent of the inorganic chlorine to active forms in the 14- to 27-km altitude range by early February 1989.
    Journal of Geophysical Research 06/1992; · 3.17 Impact Factor
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    ABSTRACT: Simultaneous measurements of the stratospheric burdens of CO2, HCN, N2O, CH4, OCS, CF2Cl2, CFCl3, CHF2Cl and HF were made by the Jet propulsion Laboratory MkIV interferometer on board the NASA DC-8 aircraft during January and early February 1989 as part of the Airborne Arctic Stratosphere Experiment. Data were acquired on 11 flights at altitudes of up to 12 km over a geographic region covering the NE Atlantic Ocean, Iceland and Greenland. The results obtained show large variations in the burdens of these tracers due to the effects of transport. The tropospheric source gas burdens were reduced inside the polar vortex, suggesting that the air had subsided with respect to the surrounding midlatitude air. Increased HF burdens inside the vortex support this interpretation. The results obtained from the different tracers are highly consistent with each other and indicate that in the 15- to 20-km altitude range inside the vortex, surfaces of constant volume mixing ratio were located some 5-6 km lower in absolute altitude than outside the vortex. The results also indicate that the magnitude of this subsidence increases with altitude. These conclusions are consistent with other measurements.
    Journal of Geophysical Research 06/1992; · 3.17 Impact Factor
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    ABSTRACT: Contents: 1. Introduction: (a) early observations and atlases; (b) measurements of atmospheric composition. 2. Analysis of absorption spectra: (a) formation of spectra; (b) molecular spectral parameters; (c) molecular catalogs. 3. Retrieval of atmospheric parameters: (a) equivalent width method; (b) nonlinear least-squares curve fitting method; (c) special problems. 4. Spectral examples: (a) prominent features: HCl, CH4, HNO3; (b) embedded and weak features: COF2, CF4, N2O5. 5. Closing remarks.
    01/1992; -1:97-151.
  • C. B. Farmer, R. H. Norton
    Planetary and Space Science 01/1992; 40:570-570. · 2.11 Impact Factor
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    ABSTRACT: About 4500 unblended CO lines have been selected and their wavenumbers accurately measured on high resolution solar spectra obtained from space with the ATMOS Fourier transform spectrometer. Half of these lines are of high rotational excitation energy and have never been observed before in the laboratory. Line positions of the fundamental bands of 12C16O have been measured up to J = 133, those of 13C16O and of 12C18O up to J = 103 and 91, respectively. The first overtone bands of 12C16O have been measured up to J = 110. These new solar CO wavenumbers, with an additional selected set of about 14 000 accurate laboratory measurements, have been simultaneously fitted to the Dunham expression utilizing 10 recently published relations between isotopically invariant parameters Uij. The present set of coefficients reproduces all accurate laboratory positions and our solar measurements of high rotational excitation with a standard deviation of about 10−5 cm−1 (300kHz). This new set is particularly recommended for all high resolution studies of infrared laboratory and stellar spectra showing CO lines of high J-values.
    Journal of Molecular Spectroscopy 10/1991; · 1.67 Impact Factor
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    ABSTRACT: Pure rotation lines of NH of the v = 0 level and v = 1 level are detected in high-resolution solar spectra obtained from the Atmospheric Trace Molecule Spectroscopy (ATMOS) experimental observations. It is pointed out that the identification of the lines is favored by the typical appearance of the triplet lines of nearly equal intensities. The observed equivalent widths of these triplet lines are compared with predicted intensities, and it is observed that these widths are systematically larger than the predicted values. It is noted that because these very faint lines are observed in a region where the signal is very low, a systematic error in the measurements of the equivalent widths cannot be ruled out; therefore, the disagreement between the observed and predicted intensities is not considered to be real.
    10/1991;
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    ABSTRACT: The isotopic composition of stratospheric water vapor and methane was investigated. Stratospheric profiles of HDO, (H-18)2O, (H-17)2O, and CH3D were derived from solar occultation spectra recorded on April 30 - May 1, 1985 by the Atmospheric Trace Molecule Spectroscopy Fourier transform spectrometer aboard Spacelab 3. The profiles of the three water-vapor isotopes showed an increase in the volume mixing ratio with altitude. The measured profiles of D/H in water vapor showed a large depletion in the lower stratosphere (about 63 percent relative to standard mean ocean water, SMOW, at 20 km) and a small increase in D/H with altitude at higher altitudes, up to 34 km. The D/H ratio in stratospheric methane was close to the corresponding isotopic ratio in SMOW.
    02/1991;
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    ABSTRACT: Accurate measurements of the positions of O- and S-branch lines of the (1-0) vibration-rotation quadrupole band of molecular nitrogen (N-14)2 are reported. Improved Dunham coefficients were derived from a simultaneous least squares analysis of these measurements and selected infrared and far infrared data. The new measurements were performed using stratospheric solar occultation spectra recorded with Fourier transform spectrometer instruments, operated at unapodized spectral resolutions of 0.002 and 0.01/cm.
    Journal of Molecular Spectroscopy 02/1991; · 1.67 Impact Factor
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    ABSTRACT: Stratospheric volume mixing ratio profiles of H{sub 2}{sup 18}O, H{sub 2}{sup 17}O, HDO, and CH{sub 3}D near latitudes of 30{degree}N and 47{degree}S have been retrieved from {approximately}0.01-cm{sup {minus}1} resolution infrared solar occultation spectra recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Spacelab 3 shuttle mission (April 29 to May 6, 1985). Improved heavy isotope water vapor and CH{sub 3}D spectroscopic parameters determined from {approximately}0.005- to 0.01-cm{sup {minus}1} resolution room temperature laboratory spectra have been used in the retrievals. The profiles of the three water vapor isotopes show an increase in the volume mixing ratio with altitude over the range of measurements (20 to 54 km for H{sub 2}{sup 18}O, 20 to 46 km for H{sub 2}{sup 17}O, and 20 to 34 km for HDO). Deuterium-to-hydrogen and heavy-to-normal oxygen isotope ratio profiles have been calculated by dividing the retrieved isotopic profiles by the previously reported profiles of H{sub 2}{sup 16}O and CH{sub 4} obtained from the same spectral data and then referencing these results to the isotopic composition of standard mean ocean water (SMOW). At 20 km the {sup 18}O/{sup 16}O ratio in H{sub 2}O is slightly depleted relative to SMOW; this ratio increases with altitude and is slightly positive above 36 km. The {sup 17}O/{sup 16}O water vapor results are similar to those for {sup 18}O/{sup 16}O. The ATMOS measurements show depletions of 63% in the D/H content of water vapor near 20 km and an increase in this ratio with altitude up to 34 km. The D/H ratio in stratospheric methane is close to the isotopic ratio in SMOW over the 18 to 28 km altitude range. No differences between the water vapor or methane isotopic compositions at the two latitudes were detected.
    Journal of Geophysical Research 01/1991; · 3.17 Impact Factor
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    ABSTRACT: The strength of S-branch lines of the N2 (1-0) electric quadrupole vibration-rotation band are determined by an analysis of solar absorption spectra. The solar data were recorded with a Fourier transform spectrometer and are characterized by high resolution, and a high signal-to-noise ratio. By extrapolating equivalent width measurements of the lines from varying air masses to zero air mass, the line strengths are found for the transitions from S7 to S10. The results presented do not include half widths and are found to be accurate to within 5 percent, and following a redetermination the N2 transitions are accurate to within 0.0002/cm. Line-of-sight atmospheric air masses associated with remotely sensed IR spectroscopic observations can be determined directly by utilizing the highly accurate data.
    Journal of Geophysical Research 01/1991; 96:13003-13008. · 3.17 Impact Factor
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    ABSTRACT: High resolution solar spectra obtained from the ATMOS Fourier Transform Spectrometer (Spacelab 3 flight on April 29-May 6, 1985) have made it possible to identify and measure a large number of lines of the vibration-rotation fundamental bands of the X2 Pi state of CH. From about 100 lines of the 1-0, 2-1, and 3-2 bands and adopting theoretical transition probabilities, a solar carbon abundance of 8.60 + or - 0.05 is derived. This value is compared with new results inferred from other carbon abundance indicators. The final recommended solar abundance of carbon is 8.60 + or - 0.05.
    Astronomy and Astrophysics 01/1991; · 5.08 Impact Factor
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    ABSTRACT: The volume mixing ratios of five minor gases (CH4, N2O, CO, H2O, and O3) have been retrieved through the middle atmosphere from the analysis of 0.01/cm resolution infrared solar occultation spectra recorded near 28 deg N and 48 deg S latitudes with the Atmospheric Trace Molecule Spectroscopy instrument, flow on board Spacelab 3 (April 30 through May 6, 1985). The results are in general agreement with reported measurements from ground-, balloon-, and satellite-based instruments for the same seasons. In detail, the vertical profiles of these gases show the effects of the upper and middle atmospheric transport patterns dominant during the season of these observations. The profiles inferred at different longitudes around 28 deg N suggest a near-uniform zonal distribution of these gases, for conditions corresponding to late spring. The sunrise occultation measurements point to a larger longitudinal variability in the vertical distribution of these gases at 48 deg S.
    09/1990;
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    ABSTRACT: A review is presented of the objectives, instrumentation, performance and results of the ATMOS program developed by NASA-JPL as part of the Spacelab 3 shuttle payload. ATMOS was developed to obtain high-resolution spectroscopic information of the middle atmosphere, from which the vertical distribution of the most possible trace and minor molecules could be retrieved. A complete occultation included not only data recorded when the optical path traversed the earth's atmosphere, but also many spectra with tangent heights big enough for no more telluric absorptions to be detected. The averaging of such 'high sun' observations has provided high quality solar spectra totally free of atmospheric absorption features.
    07/1990;

Publication Stats

2k Citations
234.71 Total Impact Points

Institutions

  • 1987–1992
    • California Institute of Technology
      • Jet Propulsion Laboratory
      Pasadena, CA, United States
    • University of Liège
      • Department of Astrophysics, Geophysics and Oceanography
      Liège, WAL, Belgium