Progress on the FT-IR measurements of water continuum in the far-infrared region at 252 – 296 K

Sung, Keeyoon

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https://hdl.handle.net/2142/100473 Copy

Description

Title

Progress on the FT-IR measurements of water continuum in the far-infrared region at 252 – 296 K

Author(s)

Sung, Keeyoon

Contributor(s)

• Wishnow, Edward H.
• Crawford, Timothy J.
• Drouin, Brian

Issue Date

2018-06-21

Keyword(s)

Mini-symposium: Far-Infrared Spectroscopy

Abstract

Water is the strongest greenhouse gas in the Earth atmosphere, which plays a critical role in the energy balance of the earth atmosphere. It has long been observed particularly in the far-infrared that there is significant longwave continuum absorption due to water vapor (dimers or multimers), not attributable to the Lorentz line contribution within 25 cm−1 from the line center for individual water vapor lines. The MT CKD model offers the water vapor continuum predictions, which are to be validated by a laboratory study in the far infrared. In order to directly measure this water vapor continuum absorption, we have obtained a series of spectra of water vapor broadened by Self, N2, and O2 in the 50 – 500 cm−1 (200 – 20 µm) at temperatures between 251 and 296 K. For this, we used a coolable White cell system (whose optics are optimized for the far-infrared spectrometry) with passive temperature control, configured to the Fourier transform spectrometer, Bruker IFS-125HR at the Jet Propulsion Laboratory (JPL). We have been analyzing the spectra to make direct measurement of the far-infrared water continuum in two steps; (1) we obtained their transmission spectra by ratioing the sample spectrum to their corresponding background spectrum, (2) we obtained the continuum part of the transmission by dividing the measured spectrum by a synthetic spectrum of the resonant lines calculated using the HITRAN database. As shown in Figure 1, it has revealed the underlying water-water, water-O2, and water-N2 continua in the temperature range, depending on the spectrum type. The preliminary results from this on-going analysis are presented along with their comparison with the MT CKD (ver.3.5) model predictions. Temperature dependence of the water vapor continuum will be discussed as part of future work.a .

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100473

DOI

10.15278/isms.2018.RI02

Copyright and License Information

Copyright 2018 Keeyoon Sung

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