Matching of high-resolution water-vapor spectra with open path FTIR field spectra

John D. Webb; Karl R. Loos; Stuart A. Reid; Joanna I.L. Hughes; S. Williamson

doi:10.1117/12.210816

31 May 1995 Matching of high-resolution water-vapor spectra with open path FTIR field spectra

John D. Webb, Karl R. Loos, Stuart A. Reid, Joanna I.L. Hughes, S. Williamson

Proceedings Volume 2365, Optical Sensing for Environmental and Process Monitoring; (1995) https://doi.org/10.1117/12.210816
Event: Optical Sensing for Environmental and Process Monitoring, 1994, McLean, VA, United States

Abstract

Optimal removal of ubiquitous water vapor spectral bands from open-path FTIR spectra is a well-known challenge. One potentially advantageous approach involves de- resolving water vapor spectra of high spectral resolution and carefully matching them to field spectra. This approach is compared with the more standard approach in which 'upwind' water vapor field reference spectra are used. Computer software implementations of these two approaches are described. A program is described that performs wavenumber scale calibration on single-beam background and measurement spectra using water vapor band frequencies prior to creating an absorbance spectrum. An iterative, interactive program is described for the de-resolution approach. It forms a specified concentration-path high-resolution water vapor spectrum, de-resolves it using Fourier spectral manipulation to a specified resolution and apodization, and allows small wavenumber shifts to be performed. The matching low resolution water vapor spectrum is subtracted from a field spectrum. A third program is described that facilitates subtraction of field water vapor spectra from field measurement spectra. Significant progress has been made in implementing the de-resolution approach, however, the field reference approach currently gives superior results, especially in the 3400-2700 cm-1 region. Further progress could be made by acquiring high- resolution water vapor spectra of higher ppm-m value and automating the procedure.

Citation Download Citation

John D. Webb, Karl R. Loos, Stuart A. Reid, Joanna I.L. Hughes, and S. Williamson "Matching of high-resolution water-vapor spectra with open path FTIR field spectra", Proc. SPIE 2365, Optical Sensing for Environmental and Process Monitoring, (31 May 1995); https://doi.org/10.1117/12.210816

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