The Water Vapor Spectrum in the Region 8600–15 000 cm−1: Experimental and Theoretical Studies for a New Spectral Line Database: I. Laboratory Measurements

Abstract

New laboratory measurements are presented for the near-infrared and visible spectrum (8600–15 000 cm−1) of water vapor. Spectral line parameters, principally intensities and air-broadening coefficients, are derived from Fourier transform spectroscopic measurements at high resolution (0.03 cm−1), a range of optical path lengths (5–513 m), and temperatures of both 252 and 296 K. Experimental line parameters are derived for 5034 assigned transitions and thorough error analysis shows parameter errors of less than 2.5% for one-third and less than 5% for over half of the lines. Calculated spectra, derived using these line parameters, reproduce the original spectra to within 2%. A comparison of the line intensities with those in the HITRAN-96 database identifies large errors in the latter with random differences that exceed a factor of two for many lines, and systematic differences between 6 and 26% depending on the water band under consideration. The recent corrections to the HITRAN database by Giver et al. (J. Quant. Spectrosc. Radiat. Transfer66, 101–105 (2000)) do not remove these discrepancies and the differences change to 6–38%. The new data are expected to substantially increase the calculated absorption of solar energy due to water vapor in climate models.