1. 1 CAVIAR meeting in NPL 2 June 2008 Water vapour continuum in near-IR band centres: Recent RAL measurements, results and problems I. Ptashnik & K. Shine (Dept. of Meteorology, University of Reading) R. McPheat & K. Smith (MSF, Rutherford Appleton Laboratory) (Acknowledges to David Paynter)

2. 2 CAVIAR meeting in NPL 2 June 2008 Water continuum in near-IR spectral region Simulated spectra for 15 mbar pure H2O, 10m, 293K / WD HWHM=25 cm -1, Keq=0.04 atm -1 (Curtiss et al., 1979) /

3. 3 CAVIAR meeting in NPL 2 June 2008  RAL_measur. - Local_lines_contribution  Recent experiment at MSF (RAL) in 1600 cm -1 H 2 O band ( * ) Department of Physical Chemistry, Hebrew University, Jerusalem

4. 4 CAVIAR meeting in NPL 2 June 2008  RAL_measur. - Local_lines_contribution  Recent experiment at MSF (RAL) in 3700 cm -1 H 2 O band

5. 5 CAVIAR meeting in NPL 2 June 2008  RAL_measur. - Local_lines_contribution  Recent experiment at MSF (RAL) in 5400 cm -1 H 2 O band

6. 6 CAVIAR meeting in NPL 2 June 2008  RAL_measur. - Local_lines_contribution  Recent experiment at MSF (RAL) in 7200 cm -1 H 2 O band

7. 7 CAVIAR meeting in NPL 2 June 2008 Precise baseline determination… Problem 1: Band wings ? ? ?

8. 8 CAVIAR meeting in NPL 2 June 2008 Precise baseline determination (pure H 2 O)… Problem 1: Band wings

9. 9 CAVIAR meeting in NPL 2 June 2008 Precise baseline determination (mixture with 1 atm air)… Problem 1: Band wings

10. 10 CAVIAR meeting in NPL 2 June 2008 Precise baseline determination… Problem 1: Band wings ? ? ?

11. 11 CAVIAR meeting in NPL 2 June 2008 Problem 2: H 2 O pressure and retrieved continuum Line Continuum  cont.  P H2O 2  cont.  (  total -  lines )   cont.  (2 - 4)   P H2O !!!

12. 12 CAVIAR meeting in NPL 2 June 2008 Problem 2: H 2 O pressure… Retrieval of water vapour pressure from the spectrum (pure H 2 O)

13. 13 CAVIAR meeting in NPL 2 June 2008 Problem 2: H 2 O pressure… Retrieval of water vapour pressure from the spectrum (pure H 2 O)

14. 14 CAVIAR meeting in NPL 2 June 2008 Problem 2: H 2 O pressure… Retrieval of water vapour pressure from the spectrum (H 2 O in 1 atm air)

15. 15 CAVIAR meeting in NPL 2 June 2008 Problem 2: H 2 O pressure… Retrieval of water vapour pressure from the spectrum (H 2 O in 1 atm air)

16. 16 CAVIAR meeting in NPL 2 June 2008 Problem 2: H 2 O pressure… Retrieval of water vapour pressure from the spectrum (H 2 O in 1 atm air)

17. 17 CAVIAR meeting in NPL 2 June 2008 Problem 2: H 2 O pressure… Retrieval of water vapour pressure from the spectrum (H 2 O in 1 atm air)

18. 18 CAVIAR meeting in NPL 2 June 2008 Problem 2: H 2 O pressure… Retrieval of water vapour pressure from the spectrum (H 2 O in 1 atm air)

19. 19 CAVIAR meeting in NPL 2 June 2008 Problem 2: H 2 O pressure… Retrieval of water vapour pressure from the spectrum (H 2 O in 1 atm air)

20. 20 CAVIAR meeting in NPL 2 June 2008 Thank you…