Infrared Spectroscopic Measurements of the Vertical Column Abundance of Sulfur Hexafluoride, SF6, From the Ground

The unresolved v3 band Q branch of sulfur hexafluoride, SF6, at 947.9 cm-1 has been identified and quantitatively analyzed in series of high-quality infrared solar spectra recorded at the International Scientific Station of the Jungfraujoch, Switzerland, and at the National Solar Observatory facility on Kitt Peak in Arizona. Series of monthly mean total vertical column abundances of SF6 above both stations, deduced from that feature with line-by-line nonlinear least squares fitting methods, are reported over the time intervals from June 1986 to June 1990 for the Jungfraujoch and from March 1981 to June 1990 for Kitt Peak. Assuming an exponential growth model for fitting these series of measurements, it is found that the vertical column abundances have increased at mean rates of 6.9 +- 2.8 %/yr above the Jungfraujoch (calculated columns of 2.99 x 10E13 molecules/cm2 in June 1986 and 3 94 x 10E13 molecules/cm2 in June 1990) and 6.6 +- 7.2 %/yr above Kitt Peak (calculated columns equal
to 2.97 x 10E13 molecules/cm2 in June 1981 and 5.38 x 10E13 molecules/cm2 in June 1990), the uncertainties corresponding to 2 sigma confidence levels. These results are further discussed within the context of variability and compared with previously published measurements.