Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5427027 | Journal of Quantitative Spectroscopy and Radiative Transfer | 2017 | 9 Pages |
â¢Water vapor self-continuum absorption measured by OF-CEAS at 2491â¯cmâ1 and by CRDS at 4435â¯cmâ1.â¢Measurements are validated using the quadratic pressure dependence of the continuum.â¢Temperature dependence studied near 2491â¯cmâ1 between 23 and 52 °C.â¢Our continuum values are much smaller than previous room temperature FTS values.â¢Significant deviations compared to the MT_CKD 3.0 model.
In a recent contribution [A. Campargue, S. Kassi, D. Mondelain, S. Vasilchenko, D. Romanini, Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model. J. Geophys. Res. Atmos., 121,13,180-13,203, doi:10.1002/2016JD025531], we reported accurate water vapor absorption continuum measurements by Cavity Ring-down Spectroscopy (CRDS) and Optical-Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) at selected spectral points of 4 near infrared transparency windows. In the present work, the self-continuum cross-sections, CS, are determined for two new spectral points. The 2491â¯cmâ1 spectral point in the region of maximum transparency of the 4.0â¯Âµm window was measured by OF-CEAS in the 23-52°C temperature range. The 4435â¯cmâ1 spectral point of the 2.1â¯Âµm window was measured by CRDS at room temperature. The self-continuum cross-sections were determined from the pressure squared dependence of the continuum absorption. Comparison to the literature shows a reasonable agreement with 1970â¯s and 1980â¯s measurements using a grating spectrograph in the 4.0â¯Âµm window and a very good consistency with our previous laser measurements in the 2.1â¯Âµm window. For both studied spectral points, our values are much smaller than previous room temperature measurements by Fourier Transform Spectroscopy. Significant deviations (up to about a factor 4) are noted compared to the widely used semi empirical MT_CKD model of the absorption continuum. The measured temperature dependence at 2491â¯cmâ1 is consistent with previous high temperature measurements in the 4.0â¯Âµm window and follows an exp(D0/kT) law, D0 being the dissociation energy of the water dimer.
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