WP2. Volatile Organic compounds and CFC- substitutes in the troposphere from FTIR spectra Task 2.1: Retrievals of CH 3 OH and CH 3 Cl Task 2.2: Re-analysis of C 2 H 4, C 2 H 6 and H 2 CO with improved spectroscopy Reunion data Team: C. Vigouroux, M. De Mazière, F. Desmet, B. Dils, C. Hermans, N. Kumps, B. Langerock, F. Scolas, (BIRA-IASB); J.-M. Metzger (Univ. La Réunion) C 2 H 4 : - Jungfraujoch data: M. Mahieu (Ulg) - IMAGES model: T. Stavrakou J.-F. Müller (BIRA-IASB) AGACC-II meeting Brussels, 18th December, 2013

Task 2.1: Retrievals of CH 3 OH and CH 3 Cl CH 3 OH: Vigouroux et al., ACP, 2012 & Stavrakou et al., ACP, 2011 In Stavrakou et al., ACP, 2011: inversion of the 2009 IASI data, in order to improve the different sources of CH 3 OH in IMAGES: - biogenic & pyrogenic sources reduced: globally 50% and 20% resp. - improved the seasonality agreement with FTIR FTIR IMAGES w/o biomass burning But, IMAGES too low in Sept-Oct.

CH 3 OH: very good correlation with CO during the biomass burning BB season (August- November; peak in October); Vigouroux et al., BB is an important source of CH 3 OH at Reunion Island IMAGES underestimates all BB species at Reunion Island in the Sept-Oct period (C 2 H 6, CO, CH 3 OH, HCOOH): - Underestimation of the fire emission database (GFED3) Short lifetime of CH 3 OH (6 d.): an underestimation of GFED3 occurs in the southern Africa/ Madagascar region. Task 2.1: Retrievals of CH 3 OH and CH 3 Cl

New: - One more year of data at St-Denis with Bruker 120M (2011) - Maïdo measurements in 2013 Confirm CH 3 OH peak in October. Few measurements at Maïdo during the BB period.  FTIR IMAGES

Task 2.1: Retrievals of CH 3 OH and CH 3 Cl CH 3 OH: summary on the seasonal cycle Overestimation of IMAGES in wet season (without optimization of sources as made in 2009 with IASI) FTIR: good agreement in the wet season (less influenced by inter-annual variability), between the 2 sites. Peak in October at both sites, smaller amplitude with IMAGES. Next version of GFED will include agricultural fires, which are (unfortunately) numerous in… Madagascar… in October !

Task 2.1: Retrievals of CH 3 OH and CH 3 Cl CH 3 Cl: first attempt of retrieval strategy: cm -1 ; spectroscopic linelist from M. Mahieu (HITRAN 2004 for CH 4, CH 3 Cl from A. Perrin) Weak spectral signature; random noise is an issue, as well as interfering species. H20H20 H20H20 CH 4, H 2 O C 2 H 6

Task 2.1: Retrievals of CH 3 OH and CH 3 Cl CH 3 Cl: improvement in the Signal to Noise Ratio from Bruker 120M to Bruker 125HR (especially after April 2013), improves the residuals. Therefore, the scatter in the CH 3 Cl columns is nicely reduced from Bruker 120M to Bruker 125HR (especially after April 2013), and at Maïdo.

Task 2.1: Retrievals of CH 3 OH and CH 3 Cl CH 3 Cl: seasonal cycle St-Denis Bruker 120M: seems too chaotic; probably we see mainly noise. St-Denis Bruker 125HR: max. in August is observed, large amplitude. Maïdo columns should be smaller than St-Denis columns ! Probably high systematic bias due to interfering species at St- Denis (H 2 O ?). Max. April and August, small amplitude.

Task 2.1: Retrievals of CH 3 OH and CH 3 Cl Maïdo columns should be smaller than St-Denis columns Comparisons St-Denis/Maïdo look better after April 2013 (when SNR was improved) Seasonal cycles in the literature: Yoshida et al., 2006 ( surface meas.): - max. in March & August at 14°S, amplitude < 5% - max. in July-August at 40°S, amplitude ~10%

Task 2.2: C 2 H 4 C 2 H 4 : many tests on retrieval strategy Final micro-window: cm -1. Very weak absorption signatures, and the strongest one is found at the edge of a CO 2 line. CO 2 St-Denis Slope:H 2 O

Task 2.2: C 2 H 4 Maïdo: improved SNR with Bruker 125 HR; less H 2 O due to altitude. CO 2 Slope:H 2 O St-DenisMaïdo Much reduced slope

Task 2.2: C 2 H 4 St-Denis (Bruker 120M): large scatter and some negative columns. Maïdo (Bruker 125HR, less H 2 O): still large scatter, no negative values. Scatter real (lifetime ~1-2 days) ? And/Or too large random error: to be calculated with SFIT4. Try more filtering ? Need more data at Maïdo.

Task 2.2: C 2 H 4 C 2 H 4 : seasonal cycle at Reunion Island St-Denis: surprising good agreement with IMAGES in Dec-Aug. (considering FTIR large scatter). Maïdo columns should be lower than St-Denis: bias due to H 2 O ? High values in April-May at Maïdo due to a few points, need to be confirmed. FTIR has a max. in Sep-Oct at both sites; not seen in IMAGES: Agreement with the (currently missing in model) biomass burning from agriculture in Madagascar ! (lifetime C 2 H 4 : 1-2 days)

Task 2.2: C 2 H 4 at Jungfraujoch C 2 H 4 at Jungfraujoch: using the Reunion Island settings. A significant negative trend is observed. Results promising ! H 2 O is much lower at Jungfraujoch.

Task 2.2: C 2 H 4 at Jungfraujoch C 2 H 4 at Jungfraujoch: seasonal cycle Phase of the seasonal cycle in agreement with IMAGES Amplitude is much larger with the model

The FTIR retrieval strategies optimized for many VOCs in the first years of AGACC-II (CH 3 OH, HCHO, HCOOH, C 2 H 6, HCN, C 2 H 2 ) have been or will be soon applied to the recent measurements. The procedure is much quicker with the tools implemented within the NORS project (B. Langerock). C 2 H 4 : a retrieval strategy has been implemented and seems promising at Jungfraujoch. Some efforts still needed at Reunion Island to understand/correct the large scatter, but seasonal cycle seems good. We are very curious to compare our Reunion Island time-series of biomass burning species with IMAGES when the GFED4 database, including agricultural fires, will be distributed ! Summary & perspectives

The quality of the spectra (SNR) has been greatly improved with the Bruker 125HR, which can be critical for molecules with low spectral signatures, close to the detection limit. At Maïdo, the altitude of the site reduces the error due to interfering species (e.g water vapor and isotopologues). CH 3 Cl: using the most recent measurements (i.e with improved SNR), it seems that there is a hope to observe this molecule. What is needed now is 1) more measurements; 2) spectroscopic tests (HITRAN2012; CH 3 Cl line-mixing); 3) better check of H 2 O interference. Perspectives for AGACCII: PAN (already tested without success up to now) and acetone will be tested with the new software (SFIT4): allows for HITRAN 2012 and for CO 2 line-mixing which was one of the problem for PAN retrievals.

Duflot, V., et al.: HCN and C 2 H 2 from IASI, AMT, Vigouroux, C.: FTIR measurements of VOCs: precious data for model and satellite validation, NDACC newsletter, Not related to AGACC-II but very important for NDACC FTIR in general, and BIRA-IASB and ULg in particular: Thanks to our work on FTIR ozone trends at 8 NDACC stations, we join the SI 2 N initiative whose aim is to provide “much improved knowledge of ozone changes for the next WMO Scientific Assessment of Ozone depletion”. - Participation in the three SI 2 N overview papers: Hassler et al.: Ozone profile measurements: techniques, uncertainties and availability, AMTD, 2013; Lambert et al.; and Harris et al., in preparation, before spring Participation in the WMO Assessment in WP 5: Outreach in 2013

Thank you !

Task 2.1: Retrievals of CH 3 OH and CH 3 Cl CH 3 Cl: first attempt of retrieval strategy, not really a big success… but some hope. Future: focus on optimizing the data after April 2013 at Maïdo and St-Denis: need more data… - Try HITRAN 2012 (with SFIT4) - Try G. Toon: CH 3 Cl line-mixing problem, propose an « empirical way » of treating this. - improve H 2 O treatment (now some spectra shows residuals) And/or filtering on systematic residuals when H 2 O is not well reproduced,…

Not related to AGACC-II but very important for NDACC FTIR in general, and BIRA-IASB in particular: Join the SI2N initiative: Over three and a half decades have passed since Molina and Rowland postulated that anthropogenic chlorofluorocarbons could deplete the ozone layer (Molina and Rowland, 1975), and over two and a half decades have passed since the discovery of the ozone hole (Farman et al., 1985). In this time, the countries of the world have produced and signed the Montreal Protocol limiting the production of ozone-depleting substances (ODSs), and leading to reductions in their atmospheric concentrations (WMO, 2011).. As we proceed towards the expected ozone recovery from the influences of ODSs, scientific questions concerning the detection and attribution of that recovery have come to the fore. Answering many of these questions will require a critical examination of the pattern and time sequence of ozone change. Thus, accurate knowledge of the altitude, latitude, and seasonal structure of the ozone response is required. It is also critical that the quality of the measurements used is as high as possible, and that the quality is known. Outreach in 2013