Network for the Detection of Stratospheric Change Fourier transform infrared intercomparison at Table Mountain Facility, November 1996

Abstract

Abstract. An intercomparison of four Fourier transform infrared (FTIR) spectrometers, operated side by side by Jet Propulsion Laboratory (JPL), National Center for Atmospheric Research, and National Physical Laboratory groups, using two different spectral fitting algorithms, was conducted at JPL's Table Mountain Facility (TMF) during November 1996. A "blind" comparison of retrieved vertical column amounts, of preselected trace gases in preselected microwindows (mw), and subsequent reanalysis of the results are described. The species analyzed are N2 (3 mw), HF (1 mw), HC1 (1 mw), CH4 (1 mw), 03 (2 mw), N20 (2 mw), HNO3 (2 mw), and CO2 (1 mw). The column agreements from the "blind" phase were within 0.5-2%, except that for HNO3, HF, and 03 the disagreement of the results was up to 10%, 5%, and 4%, respectively. It was found that several systematic effects were neglected in the "blind" phase analysis. Taking these into account in the postanalysis reduced the disagreements to 0.5-1.0% for most cases, and to less than 4%, 3%, and 1% for HNO3, HF, and 03 respectively. It was concluded that zero offsets caused by detector nonlinearity were the main cause of the large errors in HNO3 and other gases (i.e., CO2) retrieved from the HgCdTe spectra. At shorter wavelengths (i.e., HF) we conclude that incomplete modeling of the instrument line shapes (ILS) was the main cause of column differences larger than 1%.

Long‐term trends of inorganic chlorine from ground‐based infrared solar spectra: Past increases and evidence for stabilization

“…[12] Total columns retrieved with SFIT1, SFIT2, and GFIT have been compared for several molecules (including HCl) and found to agree within their respective error limits of a few percent [Goldman et al, 1999]. A comparison of profile retrievals obtained with SFIT2 and the PROFFIT algorithm adopted for retrievals from the Kiruna spectra is currently in progress.…”

“…[11] Retrievals from the Ny Å lesund and Pasadena locations relied on the ''GFIT'' software , also referred to as the ''GGG code'' by Goldman et al [1999]. The algorithm was adapted from codes initially used for the ATMOS solar occultation geometry [Norton and Rinsland, 1991] to allow retrievals of total columns from the ground, including simultaneous fitting of multiple gases.…”

The Network for the Detection of Atmospheric Composition Change (NDACC): History, status and perspectives

“…These may have gathered many instruments (ex UV-VIS), or in the case of the Infrared 5 working group (IRWG), side by side intercomparisons of several instruments including a mobile FTIR instrument were made to compare instruments and to harmonize operation procedures (e.g. Goldman et al, 1999). These typically include a blind intercomparison phase with an outside referee.…”

Validation of HNO<sub>3</sub>, ClONO<sub>2</sub>, and N<sub>2</sub>O<sub>5</sub> from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)

“…where N (z) is the number of coincidences at z, ACE i (z) is the ACE-FTS VMR at z for the ith coincident pair, and Goldman et al (1999) 166.65 • E 872.80-874.00 Vigouroux et al (2007) VAL i (z) is the corresponding VMR for the validation instrument. This mean absolute difference is plotted as a solid line in panel (b) of the comparison figures below, with ±1σ as dashed lines.…”