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CAVIAR Experimenters Meeting 2009 Liam Tallis

CAVIAR Experimenters Meeting 2009 Liam Tallis. Introduction. Lab View. Sunsets. Introduction. Introduction Assessment of the consistency of water vapour lines intensities in recent HITRAN databases Towards an absolute calibration Water Profile for Jungfraujoch Future work.

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CAVIAR Experimenters Meeting 2009 Liam Tallis

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  1. CAVIAR Experimenters Meeting 2009 Liam Tallis

  2. Introduction

  3. Lab View

  4. Sunsets

  5. Introduction • Introduction • Assessment of the consistency of water vapour lines intensities in recent HITRAN databases • Towards an absolute calibration • Water Profile for Jungfraujoch • Future work

  6. Assessment of the consistency of water vapour lines intensities in recent HITRAN databases

  7. Consistency Assessment • Analysis of the consistency of water vapour lines in recent HITRAN databases • Similar way to Casanova et. al. (2006) • Optical depth spectrum given by Where Fm is the measured signal by the FTIR, Fs is the extraterestrial irradiance given by Kurucz (1995), τm is the optical depth, θ is the solar zenith angle and k(v) is an unknown calibration factor.

  8. Consistency Assessment • Rearrangement ignoring the calibration factor (and a few other approximations) • We know have a “pseudo” optical depth spectrum • This spectrum will allow us to analyse the consistency between observation and model

  9. Consistency Assessment • Optical depth is calculated for water vapour (τw) and for five other principle absorbers in the region: CH4, CO2, O2, N2O and O3 (τg) using RFM (v4.28) • Linear fit of the “pseudo” optical depth to that calculated by RFM • Fit pseudo to the form of a x τw + b x τg + c

  10. Consistency Assessment a x τw + b x τg + c • b is tightly bound to be a value between 0.95 to 1.05 • An assumption made is other gases well know • Allowed to vary slightly for any minor error in the column amounts • c is allowed to vary more freely • c is a offset parameter that varies slowly with wavelength • a is allowed to vary between 0 and 3 • a is the important parameter • tells us the factor line intensities must be multiplied by

  11. Consistency Assessment

  12. Consistency Assessment

  13. Consistency Assessment

  14. Consistency Assessment • Camborne Field Campaign • InSb / CaF2 • Typically for 0.03cm-1 resolution spectra • Over various days, radiosondes, water columns

  15. Consistency Assessment Ratio of 3000 cm-1 - 8000 cm-1 to 8000 cm-1 – 9500 cm-1 For HITRAN04 = 0.846, St Dev= 0.011 For HITRAN08 = 0.845, St Dev= 0.010

  16. Consistency Assessment • Camborne Field Campaign • MCT / KBr • Problems! • Fit appears to be good... • But scaling factor required for water vapour lines feels wrong • Typical “a” value ~ 0.7

  17. Consistency Assessment • Camborne Field Campaign • MCT / KBr • Typically for 0.03cm-1 resolution spectra • Over various days, radiosondes, water columns

  18. Consistency Assessment

  19. Consistency Assessment

  20. Consistency Assessment

  21. TOWARDS AN ABSOLUTE CALIBRATION

  22. Towards an Absolute Calibration • Calibrations before each field campaign at NPL • NPL produce a calibration function which when used with spectral data gives an irradiance [W/m2/FT o/p unit] Calibration x Spectral Data = Calibrated Spectra • Extraterrestrial irradiance given by Kurucz’s (1995) database

  23. Towards an Absolute Calibration

  24. Towards an Absolute Calibration

  25. Towards an Absolute Calibration • We know the signal measured by the FT is given by • And thus by rearranging, we can work out the optical depth

  26. Towards an Absolute Calibration

  27. Towards an Absolute Calibration

  28. Towards an Absolute Calibration

  29. Towards an Absolute Calibration

  30. Towards an Absolute Calibration • Microtops II Sunphotometer • 13/08/2008 • AOT380 = 0.465, AOT440 = 0.486, AOT675 = 0.577, AOT936 = 0.705, AOT1020 = 0.608  • Campaign Average • AOT380 = 0.22, AOT440 = 0.17, AOT675 = 0.12, AOT936 = 0.09, AOT1020 = 0.08

  31. Towards an Absolute Calibration

  32. Towards an Absolute Calibration

  33. Water profile for Jungfraujoch

  34. Water Profile for Jungfraujoch • Radiosonde (Payerne) • Dropsonde (FAAM) • FAAM Aircraft • GPS IWV • ECMWF Forecast Fields • STARTWAVE Database, University of Bern • GPS Water Vapour • Column Water from Payerne Radiosonde

  35. Water Profile for Jungfraujoch

  36. Water Profile for Jungfraujoch

  37. Water Profile for Jungfraujoch 1st August 2009

  38. Future work

  39. Future Work • Analysis of the consistency of water vapour lines in recent HITRAN databases • Any improvements to MCT fit possible? • Repeat this style analysis for Jungfraujoch • Try with new ACE-FTS extraterrestrial line list (Hase et. al, JQSRT 2009) • Absolute Calibration • Account for difference between calibrated spectra and extraterrestrial irradiance (in atmospheric windows) • Use Reading’s RFM + DISORT Code • Water Profile for Jungfraujoch • Continued work in this area • Questions?

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