Reassessing the photochemical production of methanol from peroxy radical self and cross reactions using the STOCHEM-CRI global chemistry and transport model

Methanol (CH 3 OH) is an oxygenated volatile organic compound (VOC) and one of the most abundant species present in the troposphere. The mass of CH 3 OH in the atmospheric reservoir, its annual mass flux from sources to sinks, and its global budget have been investigated using STOCHEM-CRI, a global three-dimensional chemistry transport model. Our study shows that the global burden of methanol is 5 Tg. The atmospheric life-time of CH 3 OH is found to be 6.1 days which falls within the range of previous modelling studies. The impact of peroxy radicals on the photochemical production of CH 3 OH has been studied and suggests that NMVOCs (non-methane Volatile Organic Compounds) are an important source of both peroxy radicals and CH 3 OH. The photochemical production routes of CH 3 OH are found to be 48 Tg/yr, which are higher than the previous studies and contributes significantly to the total global methanol sources of 287 Tg/yr. An additional CH 3 OH production of 8.2 Tg/yr from the reaction of methyl peroxy radicals (CH 3 O 2 ) with hydroxyl radicals (OH) could be a significant additional source of CH 3 OH particularly over the tropical oceans which would lead to a revision of the global sources and life cycle of CH 3 OH.