Retrievals of formaldehyde from ground-based FTIR and MAX-DOAS observations at the Jungfraujoch station and comparisons with GEOS-Chem and IMAGES model simulations

Atmos. Meas. Tech., 8, 1733–1756, 2015 www.atmos-meas-tech.net/8/1733/2015/ doi:10.5194/amt-8-1733-2015 © Author(s) 2015. CC Attribution 3.0 License. Retrievals of formaldehyde from ground-based FTIR and MAX-DOAS observations at the Jungfraujoch station and comparisons with GEOS-Chem and IMAGES model simulations B. Franco1 , F. Hendrick2 , M. Van Roozendael2 , J.-F. Müller2 , T. Stavrakou2 , E. A. Marais3 , B. Bovy1 , W. Bader1 , C. Fayt2 , C. Hermans2 , B. Lejeune1 , G. Pinardi2 , C. Servais1 , and E. Mahieu1 1 Institute of Astrophysics and Geophysics of the University of Liège, Liège, Belgium 2 Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium 3 School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA Correspondence to: B. Franco () Received: 5 September 2014 – Published in Atmos. Meas. Tech. Discuss.: 23 October 2014 Revised: 25 March 2015 – Accepted: 27 March 2015 – Published: 15 April 2015 Abstract. As an ubiquitous product of the oxidation of many volatile organic compounds (VOCs), formaldehyde (HCHO) plays a key role as a short-lived and reactive intermediate in the atmospheric photo-oxidation pathways leading to the formation of tropospheric ozone and secondary organic aerosols. In this study, HCHO profiles have been successfully retrieved from ground-based Fourier transform infrared (FTIR) solar spectra and UV-visible Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) scans recorded during the July 2010–December 2012 time period at the Jungfraujoch station (Swiss Alps, 46.5◦ N, 8.0◦ E, 3580 m a.s.l.). Analysis of the retrieved products has revealed different vertical sensitivity between both remote sensing techniques. Furthermore, HCHO amounts simulated by two state-of-the-art chemical transport models (CTMs), GEOSChem and IMAGES v2, have been compared to FTIR total columns and MAX-DOAS 3.6–8 km partial columns, accounting for the respective vertical resolution of each ground-based instrument. Using the CTM outputs as the intermediate, FTIR and MAX-DOAS retrievals have shown consistent seasonal modulations of HCHO throughout the investigated period, characterized by summertime maximum and wintertime minimum. Such comparisons have also highlighted that FTIR and MAX-DOAS provide complementary products for the HCHO retrieval above the Jungfraujoch station. Finally, tests have revealed that the updated IR parameters from the HITRAN 2012 database have a cumulative ef- fect and significantly decrease the retrieved HCHO columns with respect to the use of the HITRAN 2008 compilation. 1 Introduction Formaldehyde (HCHO) is the most abundant organic carbonyl compound in the remote troposphere (Hak et al., 2005, and references therein). Being predominantly a high-yield product of oxidation by hydroxyl radicals (OH) of most of the primary volatile organic compounds (VOCs) emitted either naturally or by human activities, HCHO is ubiquitous throughout the atmosphere. It is also directly emitted in a small fraction from biogenic (e.g., vegetation), pyrogenic (mainly biomass burning) and anthropogenic (e.g., industrial emissions) sources (e.g., Carlier et al., 1986; Lee et al., 1997; Hak et al., 2005; Herndon et al., 2005; Fu et al., 2007; De Smedt et al., 2010). Long-lived VOCs such as methane (CH4 ) contribute to the background levels of HCHO. However, the spatial variability of HCHO concentration is primarily associated with the oxidation of reactive non-methane VOCs of biogenic (e.g., isoprene) or anthropogenic (e.g., butane) origin. At low nitric oxide (NO) concentrations, intermediate compounds such as methyl hydroperoxide (CH3 OOH) are formed which are partly removed by deposition, thereby reducing HCHO formation. Formaldehyde has a very short midday lifetime on the order of a few hours (Logan et al., 1981; Possanzini et al., Published by Copernicus Publications on behalf of the European Geosciences Union. 1734 B. Franco et al.: Ground-based FTIR and MAX-DOAS retrievals of formaldehyde at Jungfraujoch 2002). Its main removal pathways take place by photolysis and oxidation by OH radicals, with both loss processes yielding carbon monoxide (CO) and hydroperoxyl radicals (HO2 ), so that HCHO affects the global CO budget and the oxidative capacity of the atmosphere. Losses of HCHO by dry and wet deposition near the surface are generally less significant (Atkinson, 2000). Moreover, HCHO is an important intermediate in the VOC–HOx (hydrogen oxides)–NOx (nitrogen oxides) chemistry (Houweling et al., 1998; Hak et al., 2005; Kanakidou et al., 2005), making it a key component in the global catalytic cycle responsible for generating or destroying tropospheric ozone (O3 ), depending on the NOx levels (Fried et al., 1997; Lee et al., 1998; Tan et al., 2001). Recently, total FTIR (Fourier transform infrared) and partial UV-visible MAX-DOAS (Multi-AXis Differential Optical Absorption Spectroscopy) columns of HCHO derived from ground-based remote sensing measurements have been used to evaluate HCHO observations obtained from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY), GOME (Global Ozone Monitoring Experiment) and ACE-FTS (Atmospheric Chemistry Experiment Fourier transform spectrometer) spacebased sensors (e.g., Wittrock et al., 2006; Jones et al., 2009; Vigouroux et al., 2009; Viatte et al., 2014). Such studies reported an overall consistency between satellite HCHO observations and ground-based FTIR and MAX-DOAS measurements at a number of sites influenced by biomass burning (Wittrock et al., 2006; Jones et al., 2009; Vigouroux et al., 2009) or urban sources of pollution (Wittrock et al., 2006). In addition, Vigouroux et al. (2009) successfully compared FTIR and MAX-DOAS observations, HCHO columns from SCIAMACHY nadir satellite and simulations by the global CTM (chemistry transport model) IMAGES v2 (Intermediate Model of Annual and Global Evolution of Species) at Reunion Island (20.9◦ S, 55.5◦ E). In this study, we report parallel HCHO measurements performed at the high-altitude research station of Jungfraujoch (Swiss Alps), part of the NDACC (Network for the Detection of Atmospheric Climate Change; see http://www.ndacc.org), using both ground-based high-resolution FTIR and MAXDOAS instruments. This work presents the first intercomparison of ground-based FTIR and MAX-DOAS HCHO observations carried out at a high-altitude, dry and weakly polluted site (Zander et al., 2008). The Jungfraujoch station contrasts with, e.g., the sea-level Reunion Island site where HCHO total columns are influenced by large precursor emissions originating from biogenic and pyrogenic sources in southern Africa and Madagascar (Vigouroux et al., 2009). The combination of elevation, weakly polluted conditions and the strong vertical gradient of HCHO concentration in the lower troposphere contributes to reducing the solar infrared absorption of HCHO at the Jungfraujoch station and makes it very challenging (...truncated)