Peroxy radical partitioning during the AMMA radical intercomparison exercise

Abstract

Abstract. Peroxy radicals were measured onboard two scientific aircrafts during the AMMA (African Monsoon Multidisciplinary Analysis) campaign in summer 2006. This paper reports results from the flight on 16 August 2006 during which measurements of HO 2 by laser induced fluorescence spectroscopy at low pressure (LIF-FAGE) and total peroxy radicals (RO * 2 = HO 2 + RO 2 , R = organic chain) by two similar instruments based on the peroxy radical chemical amplification (PeRCA) technique were subject of a blind intercomparison. The German DLR-Falcon and the British FAAM-BAe-146 flew wing tip to wing tip for about 30 min making concurrent measurements on 2 horizontal level runs at 697 and 485 hPa over the same geographical area in Burkina Faso. A full set of supporting measurements comprising photolysis frequencies, and relevant trace gases like CO, NO, NO 2 , NO y , O 3 and a wider range of VOCs were collected simultaneously.Results are discussed on the basis of the characteristics and limitations of the different instruments used. Generally, no data bias are identified and the RO * 2 data available agree quite reasonably within the instrumental errors.

Technical Note: Characterisation of a DUALER instrument for the airborne measurement of peroxy radicals during AMMA 2006

“…3.3. There is no information available about the relative distribution of peroxy radicals during AMMA except for the radical intercomparison exercise (Andrés Hernández et al, 2010) where the HO 2 /RO 2 ratio remained close to 1:1. Complementary modeling results indicated that CH 3 O 2 represents 90% of the alkyl peroxy radicals present .…”

An aircraft based three channel broadband cavity enhanced absorption spectrometer for simultaneous measurements of NO<sub>3</sub>, N<sub>2</sub>O<sub>5</sub> and NO<sub>2</sub>

“…The square root of the Allan variance, termed the Allan deviation, provides an indication of the instrument stability (Allan, 1966;Werle et al, 1993). The Allan deviation plots for each of the BBCEAS instrument's measurement channels are shown in Fig.…”

“…These gases are of interest due to their participation in a range of atmospheric processes: oxidation by NO 3 controls the lifetimes of some species, including a number of volatile organic compounds (VOCs) that are important for photochemical ozone production, while deposition of N 2 O 5 onto certain aerosol surfaces represents a potentially important but presently unquantified sink of diurnally aggregated NO x (Chang et al, 2011). The BBCEAS instrument is one of a suite of instruments on board the United Kingdom's BAe 146-301 Facility for Airborne Atmospheric Measurements (FAAM) research aircraft, which collectively provide comprehensive characterisation of a range of important trace gases and aerosol species (Pfister et al, 2006;Capes et al, 2009;Johnson et al, 2009;Lewis et al, 2007;Andrés-Hernández et al, 2010).…”

Detection of HO<sub>2</sub> by laser-induced fluorescence: calibration and interferences from RO<sub>2</sub> radicals

“…It applies chemical conversion of HO 2 to OH at reduced pressure and detects OH by LIF (see review, Heard and Pilling, 2003). Chemical conversion combined with radical amplification H. Fuchs et al: HO 2 by LIF: calibration and interference from RO 2 is used by Peroxy Radical Chemical Amplifier (PERCA) (Cantrell et al, 1984;Hastie et al, 1991;Clemitshaw et al, 1997;Burkert et al, 2001;Sadanaga et al, 2004;Mihele and Hastie, 2000;Green et al, 2006;Andrés-Hernández et al, 2010) and Peroxy Radical Chemical-Ionization Mass Spectrometry (ROxMas, PerCIMS) (Hanke et al, 2002;Edwards et al, 2003;Hornbrook et al, 2011), in order to achieve high measurement sensitivities for HO 2 . All indirect techniques (LIF, PERCA and ROxMas/PerCIMS) make use of the conversion reaction between HO 2 and NO, in order to produce OH.…”