Open AccessHO x budgets during HOxComp: A case study of HO x chemistry under NO x ‐limited conditions
Author(s) -
Elshorbany Y. F.,
Kleffmann J.,
Hofzumahaus A.,
Kurtenbach R.,
Wiesen P.,
Brauers T.,
Bohn B.,
Dorn H.P.,
Fuchs H.,
Holland F.,
Rohrer F.,
Tillmann R.,
Wegener R.,
Wahner A.,
Kanaya Y.,
Yoshino A.,
Nishida S.,
Kajii Y.,
Martinez M.,
Kubistin D.,
Harder H.,
Lelieveld J.,
Elste T.,
PlassDülmer C.,
Stange G.,
Berresheim H.,
Schurath U.
Publication year - 2012
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jd017008
Subject(s) - diurnal temperature variation , isoprene , analytical chemistry (journal) , daytime , atmospheric sciences , physics , chemistry , environmental science , meteorology , environmental chemistry , nuclear magnetic resonance , copolymer , polymer
Recent studies have shown that measured OH under NO x ‐limited, high‐isoprene conditions are many times higher than modeled OH. In this study, a detailed analysis of the HO x radical budgets under low‐NO x , rural conditions was performed employing a box model based on the Master Chemical Mechanism (MCMv3.2). The model results were compared with HO x radical measurements performed during the international HOxComp campaign carried out in Jülich, Germany, during summer 2005. Two different air masses influenced the measurement site denoted as high‐NO x (NO, 1–3 ppbv) and low‐NO x (NO, < 1 ppbv) periods. Both modeled OH and HO 2 diurnal profiles lay within the measurement range of all HO x measurement techniques, with correlation slopes between measured and modeled OH and HO 2 around unity. Recently discovered interference in HO 2 measurements caused by RO 2 cross sensitivity was found to cause a 30% increase in measured HO 2 during daytime on average. After correction of the measured HO 2 data, the model HO 2 is still in good agreement with the observations at high NO x but overpredicts HO 2 by a factor of 1.3 to 1.8 at low NO x . In addition, for two different set of measurements, a missing OH source of 3.6 ± 1.6 and 4.9 ± 2.2 ppb h −1 was estimated from the experimental OH budget during the low‐NO x period using the corrected HO 2 data. The measured diurnal profile of the HO 2 /OH ratio, calculated using the corrected HO 2 , is well reproduced by the MCM at high NO x but is significantly overestimated at low NO x . Thus, the cycling between OH and HO 2 is better described by the model at high NO x than at low NO x . Therefore, similar comprehensive field measurements accompanied by model studies are urgently needed to investigate HO x recycling under low‐NO x conditions.