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1 Water vapour self-continuum in windows: Processing the recent MSF RAL measurements Igor Ptashnik University of Reading CAVIAR semi-annual meeting 29.09.2010.

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Presentation on theme: "1 Water vapour self-continuum in windows: Processing the recent MSF RAL measurements Igor Ptashnik University of Reading CAVIAR semi-annual meeting 29.09.2010."— Presentation transcript:

1 1 Water vapour self-continuum in windows: Processing the recent MSF RAL measurements Igor Ptashnik University of Reading CAVIAR semi-annual meeting NPL, London

2 2 Saturated P H2O (mb) T (K)P H2O (mb) (F), 20(F) (F), 50(F), 300 F (F), 400, 600 F, F,1000, 1500 F, F,1000, 1500,2000, 3000, ,2000, 3000, 4000, 5000 Resolution (cm -1 ): N of scans: : MSF RAL measurements (R. McPheat, K. Smith, G. Willaims) Pure H2O measurements (self-continuum) 1) empty cell 2) Argon (same pressure as H 2 O in step 3) 3) pure H 2 O (same pressure as in step 2) 4) Argon (same pressure as H 2 O in step 3) 5) empty cell

3 3 MSF RAL measurements (R. McPheat, K. Smith, G. Willaims) Optical depth Baseline error usually did not exceed 0.5% Spectral resolution high enough to resolve separate lines Baseline accuracy ILS

4 4 Processing MSF RAL measurements Continuum small as compared to the lines in microwindows Continuum is strong as compared to the lines in microwindows

5 5 Processing MSF RAL measurements Retrieved experimental self-continuum in windows is an order of magnitude stronger than MTCKD in model. For 2500 cm -1 and 4600 cm -1 windows the disagreement increases with temperature, reaching a factor 25 at 470 K.

6 6 There is a reasonably good agreement with the previous high-T measurements by Burch & Alt (1984) and Hartmann et al. (19993). However, at lower T-s Burch's data starts underestimating continuum, while Baranov & Lafferty data is a factor 2 higher than ours at 350K. Processing MSF RAL measurements Baranov & Lafferty, 350 K

7 7 Temperature dependence. Simple analysis.

8 8

9 9 Slope (i.e. D o ) is varying: from max K ( cm -1, lower T-s; cm -1, higher T-s); to min K ( cm -1, higher T-s). Slope (i.e. Do): 1770 K – max slope (6200 cm -1, high T); 1066 K (5900 cm -1 ); 587 K (2500 cm-1, high T); 1030 K (2500 low T); 1713 K (2600 cm, 2 lowest T); 1800 K (Baranov)


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