1. CH 4 retrievals : status of Ulg work HYMN Workshop, Totnes, 22-24 October 2007 Liège team Ph. Demoulin, P. Duchatelet, E. Mahieu, Ch. Servais, S. Trabelsi, R. Zander, G. Roland, J. Bosseloirs, O. Flock, V. Vandeweerdt

2. Content 1. Part I : CH 4 retrievals tests performed on a « new » µwindow – comparisons with the UFTIR procedure 2. Part II : CH 4 isotoplogues ( 13 CH 4 and CH 3 D) µwindows selection – info content – first results

3. Part I : CH 4 retrievals

4. µwindows [cm -1 ] Interf. species CH 4 line # E’’Remarks 2613.70-2615.40 2650.60-2651.30 2835.50-2835.80 2903.60-2904.03 2921.00-2921.60 CO 2,HDO,sun CO 2,HDO none NO 2 H 2 O,HDO, NO 2, sun 2211122111 10/31 105/31 63 220 293 UFTIR µwindows 2741.80-2743.10CO 2,HDO,O 3,sun4220 « New » µwindow suggested by Corinne Vigouroux in Ténérife (May 2007) 2741.80-2743.10 2835.50-2835.80 2903.60-2904.03 CO 2,HDO,O 3,sun none NO 2 411411 220 63 220 « New » µwindow + 2 UFTIR µwindows CH 4 retrievals : an overview of existing procedures

5. CH 4 retrievals : input sources HITRAN-04 a priori CH 4 profile from HALOE (~46°N / 1995 annual mean) a priori CH 4 variability from HALOE (diagonal matrix) high (2.85 mK) & low (4.96 mK) resolution FTIR spectra only FTIR spectra with SZA smaller than 80° SNR value for inversions = 500 41 layers scheme Retrieval algorithm : SFIT-2 v.3.91

7. CH 4 retrievals : typical info content ApproachDOFS λ 1 to λ 4 Total error on columns (%) 5 UFTIR 2.62 2.4* 0.99 0.92 0.58 0.10 2.07 for [3.58-7] km 1.36 for [7-17 ] km 1.96 for [17-27] km 0.28 for [3.58-100] km «New» 3.13 3.0* 1.00 0.97 0.82 0.31 1.55 for [3.58-7] km 1.14 for [7-17 ] km 1.88 for [17-27] km 0.13 for [3.58-100] km «New» + 2 UFTIR 3.18 3.1* 1.00 0.97 0.84 0.33 1.54 for [3.58-7] km 1.13 for [7-17 ] km 1.86 for [17-27] km 0.13 for [3.58-100] km Simulation performed with a spectrum recorded at ISSJ on 30 March 2003-SZA=51°-4.96mK (*) : DOFS values obtained by Corinne for SZA=51° / SNR=250

8. CH 4 retrievals : info content ApproachDOFS 5 UFTIR2.97 ± 0.24 «New»3.31 ± 0.14 «New» + 2 UFTIR3.40 ± 0.15 Mean DOFS values averaged over the whole 2003 year (~550 spectra)  The 2 last approaches allow to slightly increase DOFS

9.  No significant advantage to add the 2 UFTIR µwindows to the « new » one (see lower-state energy, DOFS, AvK)

10. CH 4 retrievals : daily means for 2003 [(New-UFTIR)/UFTIR]*100 = 0.11±0.44 % [Corinne found a bias of ~3%]

11. CH 4 retrievals : mean profiles for 2003  significant differences in the troposphere

12. CH 4 retrievals : daily means for 2003 [(New-UFTIR)/UFTIR]*100 = 6.47±2.05 %

13. CH 4 retrievals : inter-layer correlation no ILC parameter has been used here so far Corinne uses an ILC = 4km for the whole altitude range M.Schneider et al. (ACP, 2005) adopts an ILC = 2.5km  Do these values look reasonnable ?

14. CH 4 correlation matrices derived from ACE-FTS Tropospheric part 57 ACE profiles used ILC ~1.5 km Stratospheric part 422 ACE profiles used ILC between 2 and 4 km

15. CH 4 retrievals : conclusions a new µwindow for CH 4 retrievals has been tested. This µwindow provides higher info content than the selection of µwindows adopted by the UFTIR community; lines adopted in the new approach are also more consistent in terms of T dependance for CH 4 total columns, the new approach doesn’t introduce any bias relative to the UFTIR approach a bias is however observed on retrieved VMR profiles as well as on partial columns in the troposphere oscillations in retrieved CH 4 profiles don’t disappear more investigations needed concerning ILC : which ILC value to adopt ? Which impact on DOFS/ retrievals results ?

16. Part II : CH 4 isotoplogues ( 13 CH 4 and CH 3 D)

17. 13 CH 4 study – a selection of µwindows in the InSb range Inputs & µwindows selection

18. Target species µ-windows [cm -1 ] Interf. species 13 CH 4 line # Lower state E ’’ [cm -1 ] 13 CH 4 2817.38-2817.52 2846.15-2846.71 2892.45-2892.75 2924.15-2925.10 none CH 4,HDO,H 2 O,sun CH 4,HDO,H 2 O,NO 2 CH 4,HDO,H 2 O,NO 2, OCS,O 3,sun 12221222 157 63/63 157/157 4 µ-windows fitted simultaneously a priori profile derived from ACE-FTS ([41-51]°N / 2004-2006) a priori variability derived from ACE-FTS (diagonal matrix) high (2.85 mK) & low (4.96 mK) resolution FTIR spectra only FTIR spectra with SZA [70-80]° HITRAN-04 and SFIT-2 v3.91

19. 13 CH 4 study – a selection of µwindows in the InSb range Interfering species [simulations performed for a SZA = 75°]

21. 13 CH 4 study – a selection of µwindows in the InSb range Information content

22. #µwindows [cm -1 ] DOFS λ1λ1 12817.38-2817.520.210.20 22846.15-2846.710.470.41 32892.45-2892.750.580.48 42924.15-2925.100.480.41 All1.050.77 Typical values obtained from a spectra recorded @ ISSJ (04/04/2005 - SZA~77°- 4.96 mK)

24. 13 CH 4 study – a selection of µwindows in the MCT range Inputs & µwindows selection

25. Target species µ-windows [cm -1 ] Interf. species 13 CH 4 line # Lower state E ’’ [cm -1 ] 13 CH 4 1234.04-1234.44 CH 4,CO 18 O,COF 2 1575 a priori profile derived from ACE-FTS ([41-51]°N / 2004-2006) a priori variability derived from ACE-FTS (diagonal matrix) high (4 mK) & low (6.1 mK) resolution FTIR spectra only FTIR spectra with SZA [65-80]° HITRAN-04 and SFIT-2 v3.91

26. 13 CH 4 study – a selection of µwindows in the MCT range Interfering species [simulations performed for a SZA = 75°]

28. 13 CH 4 study – a selection of µwindows in the MCT range Information content

30. 13 CH 4 study – a selection of µwindows First results

33. 13 CH 4 study – a selection of µwindows Conclusions

34. We have selected two sets (InSb range/MCT range) of µwindows allowing to derive 13 CH 4 abundances Each set contains enough sensitivity to retrieve one partial column/VMR profile between 5 and 14 km, with at least 80% of the information coming from the measurement We have observed a significant bias of ~5% on partial columns/VMR profiles between the InSb and the MCT ranges However, due to higher information content, wider SZA range for the retrievals (  more data points available) and smaller perturbation by interfering species (e.g. H 2 O or HDO), we recommend the use of the MCT line for the 13 CH 4 retrievals

35. CH 3 D study – a selection of µwindows Inputs & µwindows selection

36. CH 3 D Center (cm -1 )Interfering species 2951.00H 2 O O 3 CH 4 2960.43H 2 O O 3 CH 4 3061.46H 2 O O 3 CH 4 3065.06H 2 O O 3 CH 4 3070.80H 2 O O 3 CH 4 3072.65O 3 CH 4 3078.40H 2 O O 3 CH 4 3089.53O 3 CH 4 3091.30H 2 O O 3 CH 4 3100.30H 2 O O 3 CH 4 3106.41H 2 O O 3 CH 4 CH 3 D lines used by ATMOS http://remus.jpl.nasa.gov/atmos/atmosversion3/gaswindows.html#CH3D #1 #2 #3 #4

37. Target species µ-windows [cm -1 ] Interf. species CH 3 D line # Lower state E ’’ [cm -1 ] CH 3 D 2950.77-2951.00 3070.71-3071.00 3072.70-3073.15 3089.15-3089.70 HDO,H 2 O,O 3 CH 4,O 3 CH 4,H 2 O,O 3,sun CH 4,H 2 O,O 3 12121212 266 163/138 151 285/266 a priori profile derived from ACE-FTS ([41-51]°N / 2004-2006) a priori variability derived from ACE-FTS (diagonal matrix) high (2.85 mK) & low (4 and 4.96 mK) resolution FTIR spectra only FTIR spectra with SZA [70-80]° HITRAN-04 and SFIT-2 v3.91

38. #µ-windows [cm -1 ]DOFS λ1λ1 12950.77-2951.250.320.28 23070.71-3071.000.510.43 33072.70-3073.150.510.44 43089.15-3089.700.500.43 All1.000.76  single µ-window (#2) and multi spectra strategy ? Typical values obtained from a spectra recorded @ ISSJ (15/01/2005-SZA~79°- 4.96 mK)  multi µ-windows or single µ-window (#2) strategy ?

39. ApproachDOFS λ1λ1 RMS of µw #2 #20.4 ± 0.1[0.19 – 0.60]0.18 ± 0.04 #2 with multispectra 0.8 ± 0.2[0.35 – 0.80]0.18 ± 0.04 4 µw0.9 ± 0.1[0.49 – 0.87]0.20 ± 0.04 Complete statistics for year 2005 (373 spectra) 28

40. CH 3 D total columns for year 2005

41. Still difficult to conclude which approach (multi- µwindows or single µwindow with multi-spectra) is the best !  To test the multi-µwindows approach on FTIR spectra recorded at low altitude sites could be helpfull The consistency between the 2 approaches is good and multi-µwindows provides higher info content but what about water vapor interferences for lower altitude sites ??