1. ACE Spectroscopic Issues for the Atmospheric Chemistry Experiment (ACE) Chris Boone, Kaley Walker, and Peter Bernath HITRAN meeting June, 2008

2. ACE Atmospheric Chemistry Experiment n Satellite mission for remote sensing of the Earth’s atmosphere, with a primary focus on Arctic ozone n Developed by the Canadian Space Agency n Launched August 2003, science operations began February 2004 n Operating well, no major problems yet. n Currently funded through April 2009.

3. ACE Solar Occultation

4. ACE Instruments n Infrared Fourier Transform Spectrometer operating between 2 and 13 microns with a resolution of 0.02 cm -1 (  25 cm MPD) n 2-channel visible/near infrared Imagers, operating at 0.525 and 1.02 microns n UV / Visible spectrometer (MAESTRO) 0.285 to 1.03 microns, resolution ~1-2 nm n Suntracker n Startracker

5. ACE ACE-FTS (ABB-Bomem) Interferometer-sideInput optics-side

6. ACE SNR Courtesy of Ryan Hughes

7. ACE CO 2 microwindows Discarded 14 CO 2 microwindows.

8. ACE Scale CO 2 microwindows? HITRANScaled intensities Retrievals from a single microwindow, average of 95 occultations Sticking with HITRAN.

9. ACE HNO 3 Internal Consistency Reduce all HNO 3 line intensities in the 1700 cm -1 region by 8.5% for version 3.0 processing. From November 2007 June 2008, verifying that we used the updated HNO 3 parameters

10. ACE CF 4 residuals Large residuals from HNO 3. Similar issues with ClONO 2.

11. HNO 3 Spectroscopy Evaluation Geoffrey Toon Jet Propulsion Laboratory California Institute of Technology In July 2006, HITRAN released a complete replacement for HNO 3, based on the work of Flaud et al., [2006] “MIPAS database: Validation of HNO 3 line parameters using MIPAS satellite measurements”, ACP, 6, 5037-5048, 2006 How well does this new linelist describe the HNO 3 absorption?

12. HNO 3 ground-state bands 458.2 nu9 580.3 nu7 646.8 nu6 763.2 nu8 879.1 nu5 896.4 2nu9 1031.5 nu7 + nu9 1100.4 nu6 + nu9 1166.3 2nu7 1205.0 nu8 + nu9 1224.6 nu6 + nu7 1288.0 2nu6 1303.2 nu4 1326.2 nu3 1334.6 nu5 + nu9 1340.8 nu7 + nu8 1407.2 nu6 + nu8 1456.5 nu5 + nu7 2467.9 nu2 + nu8 2583.5 nu2 + nu5 2601.2 2nu4 2624.1 nu3 + nu4 2645.1 2nu3 3006.8 nu2 + nu4 3029.7 nu2 + nu3 3412.4 2nu2 3551.7 nu1 4006.9 nu1 + nu9 4123.7 nu1 + nu7 4190.1 nu1 + nu6 4306.3 nu1 + nu8 4421.9 nu1 + nu5 4845.2 nu1 + nu4 4868.1 nu1 + nu3 5250.8 nu1 + nu2 7089.2 2nu1 1515.8 nu5 + nu6 1533.3 2nu8 1639.0 nu5 + nu8 1709.6 nu2 1756.7 2nu5 1757.9 nu4 + nu9 1789.2 nu3 + nu9 1879.7 nu4 + nu7 1902.7 nu3 + nu7 1918.1 nu4 + nu6 1949.1 nu3 + nu6 2061.3 nu4 + nu8 2092.2 nu3 + nu8 2140.5 nu2 + nu9 2177.9 nu4 + nu5 2200.9 nu3 + nu5 2285.3 nu2 + nu7 2351.7 nu2 + nu6 Bold indicates present in July 2006 HITRAN update

13. Examples of missing HNO 3 bands Fits to MkIV balloon spectra acquired at 22-23 km tangent altitude inside the polar winter vortex showing various missing HNO 3 bands. nu1+nu9 nu1 2nu3

14. HNO 3 Summary (Geoff Toon) July 2006 HNO 3 update is an improvement on HITRAN 2004: Reduced inconsistencies between 900 and 1700 cm -1 bands Improved fits to the 900 and 1200 cm -1 regions Introduced a J-dependent widths (900 cm -1 region only) But serious deficiencies remain: nu 3 band at 1300 cm -1 (the strongest) is still problematic Strength of 1205 cm -1 band is too small (20%) No lines above 1770 cm -1 (e.g. nu 1 fundamental at 3550 cm -1 ) Missing the vast majority of overtone and combination bands, Missing most hot bands and all heavy isotopologs HNO 3 widths are all constant, except for the 900 cm -1 region HNO 3 spectroscopic deficiencies are a major obstacle to further progress in the use of solar occultation spectra to measure or detect trace gases (e.g. SO 2, HDO, H 2 CO, HOCl, OH, HO 2 )

15. ACE Pseudolines COCl 2 COClF Eventually want real spectroscopic parameters (or cross sections) for these molecules. For now, pseudolines allow retrievals.

16. ACE H 2 O spectroscopic parameters n Below about 15 km, H 2 O lines in the ACE- FTS spectra exhibit bad w-shaped residuals. n At least partially deviations from the Voigt lineshape, but there could also be a contribution from poor spectroscopic parameters (very weak lines). n Very bad consistency between lines. n Determine parameters from the ACE-FTS spectra (not the ideal solution).

17. ACE H 2 O (continued) n Parameters of interest are the pressure broadening (including a temperature dependence), intensity, and pressure shift. n Using many different occultations, initially attempted to determine both broadening parameter and its temperature dependence, but that didn’t work out well (took a week to converge, sometimes didn’t converge). n Fix temperature dependence (HITRAN). n Choose a single line for “calibration.”

18. ACE HITRAN: pbhw = 0.0927 NEW: pbhw = 0.1000 All residuals shown are from sr10909 (a tropical occultation).

19. ACE Does changing broadening parameters affect VMR? Change intensity by ~3%? Still debating this one.

20. ACE HITRAN: pbhw = 0.0845, strength = 6.21e-24, pshift = 0.00151 NEW: pbhw = 0.1004, strength = 6.71e-24 (+8%), pshift = -0.0190 Use the line at 1987.34 cm -1 to calibrate those at lower altitudes. Note: minimal occultation set. Final values will be derived from a set of 95 tropical occultations before after Simultaneously fit with the line at 1987.34 cm -1 using multiple rays across the field of view.

21. ACE Internal consistency? The line at 1987.34 cm -1 would have been more consistent with the other two strong lines without the change in broadening parameter. Note: different # of data points averaged for the two lines for this altitude

22. ACE HITRAN: pbhw = 0.0814, strength = 1.4e-24 NEW: pbhw = 0.0986, strength = 2.83e-24 (+102%) before after H2OH2O

23. ACE HITRAN: pbhw = 0.0702, strength = 2.98e-24 NEW: pbhw = 0.0877, strength = 4.09e-24 (+37%)

24. ACE Big changes in the weakest H 2 O lines Line (cm-1) HITRAN pbhw NEW pbhw HITRAN strength NEW strength strength change HITRAN pshift NEW pshift 1959.63.0845.10076.21e-246.71e-24+8%.00151-.0188 955.25.0702.08772.98e-244.09e-24+37% 1207.27.0814.09861.40e-242.83e-24+102% 941.02.0732.08721.88e-242.75e-24+46% 944.86.0419.04691.26e-241.87e-24+48% 944.95.0358.04854.24e-257.43e-25+75% 955.69.0407.04961.63e-242.32e-24+42%.00006-.00318 1214.96.0768.09297.75e-248.37e-24+8% 2732.49.0651.08219.84e-251.70e-24+73% 2912.38.0660.07875.93e-251.12e-24+89% 2912.47.0688.07633.58e-244.32e-24+21%

25. ACE H 2 O summary n Huge changes in intensities for the lines used to retrieve H 2 O at lowest altitudes. n Generate parameters from 95 tropical occultations (instead of just 4). n H 2 O is an interference for a lot of other molecules in the troposphere. Try to improve the spectroscopic parameters for those H 2 O lines as well.

26. ACE CH 4 line mixing? Red curve is the contribution in the window from NO 2. Line mixing in weak CH 4 lines could yield problems with low altitude NO 2, HCl, and CH 4, plus weak absorbers H 2 CO, CH 3 Cl, acetone,….

27. ACE C2H6C2H6C2H6C2H6 Residuals in CH 3 Cl window (near 2967 cm -1 ) without C 2 H 6. Red curve is the C 2 H 6 contribution in this window, calculated from Geoff Toon’s pseudolines. No C 2 H 6 data near 2967 cm -1 for HITRAN (including C 2 H 6 update). Lack of C 2 H 6 in calculated spectrum yields overestimate of CH 3 Cl

28. ACE CFC-12 ? Near 922 cm -1 Near 1161 cm -1

29. ACE Lineshape problem in CO? CO lines

30. ACE HCl calibration? HITRAN HCl Residuals with HCl line 2981.0017  2981.0001 cm -1 2703.0114  2703.0098 cm -1 2752.0364  2752.0346 cm -1 HCl problem or other molecules?

31. ACE Summary n HNO 3 problems. Internal consistency. Bad residuals degrading results for other molecules, preventing SO 2 retrievals. n HNO 3 pseudolines to allow SO 2 retrieval? n H 2 O weak lines exhibit poor internal consistency, causes accuracy problems with ACE tropospheric H 2 O retrievals. n Fix C 2 H 6, especially missing data regions. n CH 4 line mixing parameters for weak lines.