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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)

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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) /

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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

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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

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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

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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

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

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

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

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

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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 !!!

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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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)

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20 CAVIAR meeting in NPL 2 June 2008 Thank you