1 / 10

Current status on the continuum derived from MSF RAL data

Current status on the continuum derived from MSF RAL data. Igor V. Ptashnik Department of Meteorology, University of Reading Leicester, 24 September 2009. (JGR, in print). . .  +. 2 . CAVIAR measurements at MSF RAL: 1200 - 8000 cm -1.

matana
Download Presentation

Current status on the continuum derived from MSF RAL data

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Current status on the continuum derived from MSF RAL data Igor V. Ptashnik Department of Meteorology, University of Reading Leicester, 24 September 2009

  2. (JGR, in print)   + 2 CAVIAR measurements at MSF RAL:1200 - 8000 cm-1

  3. CAVIAR measurements at MSF RAL:1200-8000 cm-1 Sophisticated ab initio calculations of water dimer spectra at close to room-temperatures are required.

  4. 2) Strong negative T-dependence: Roberts, Selby, Biberman(Appl.Opt., 1976): MT_CKD continuum model (1989): Vigasin (JQSRT, 2000), water dimer model: Under investigation… CAVIAR measurements at MSF RAL Retrieval of the in-band water vapour self-continuum 1) Quadratic PH2O-dependence:Cs (PH2O)2 Converting to the "continuum" units 3) Well pronounced spectral features

  5. Arguments for the dimers (in the band centres) 1) The spectral features of the derived continuum are: • too large to be explained by possible uncertainties/errors in water vapour line parameters in HITRAN or by any known deviation from Voigt profile (Dicke narrowing, Line mixing etc.); • coincide reasonably well with known ab initio predictions and low-T matrix measurements of water dimers fundamental and combinational bands; this often includes expected frequency shift towards smoothed water monomer spectral features; • not described by any conventional continuum model; • have expected from dimer theory P- and T-dependence. 2) Partitioning of the pair states in phase space(Epifanov & Vigasin, 1997; Schenter et al., 2002): The role of free pair states is almost negligible at near room temperatures; metastable and true bound states should dominate instead.

  6. Measurements at MSF RAL:Water continuum in band wings First estimation of the continuum absorption was made in the far band wings. Nearly an order of magnitude larger absorption than predicts MT_CKD model! However, so far uncertainty is too big and further work is required. RAL has been carrying out new high-pressure measurements…

  7. Measurements at MSF RAL:Water continuum in band wings First estimation of the continuum absorption was made in the far band wings. Nearly an order of magnitude larger absorption than predicts MT_CKD model! However, so far uncertainty is too big and further work is required. RAL has been carrying out new high-pressure measurements…

  8. Measurements at MSF RAL:Band wings (3.8 mcr) 2.1 mcr 3.8 mcr Very good agreement with recent measurements by Baranov & Lafferty at NIST in 3.8 mcr window from 293 to 351K, and with Lorentzian-shape approximation for WD band wings (light blue line).

  9. Measurements RAL (MSF) FTS Camb/Leics CDRS NPL, FTS MetOffice, ARIES MetOffice, SWS Imperial, TAFTS visiblenear IRmid IRfar IR CAVIAR measurements • Laboratory (reference!) and field high-resolution measurements all over the spectral region from visible to far infrared

  10. Conclusions • RAL measurements gave us firm evidence of dominating water dimer contribution to the water vapour self-continuum within near-IR water vapour bands. • The continuum absorption in the middle- and near-IR windows is still uncertain and must be one of the main (and urgent!) priorities for the current CAVIAR investigation at RAL. • Sophisticated ab initio calculations of water dimer spectra at room-temperatures are necessary to compare with experimental continuum. Thank you…

More Related