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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 17, 1881, doi:10.1029/2003GL017167, 2003

Biogenic methanol and its impacts on tropospheric oxidants

Xuexi Tie

National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA


Alex Guenther

National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA


Elisabeth Holland

National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA


Abstract

We use a global chemical transport model (MOZART-2) to estimate the effects of surface emissions of methanol on tropospheric oxidants. The importance of methanol in tropospheric chemistry is two fold. First, methanol has a relatively large surface emission with an estimated global emission of 70 to 350 Tg methanol/year. The estimated methanol flux is comparable to other major hydrocarbon surface emissions such as isoprene and total monoterpenes, but the chemical lifetime of methanol is several days (in the boundary layer) to a few weeks (in the upper troposphere), which is much longer than the chemical lifetime of isoprene or monoterpenes (For example, the chemical lifetime of isoprene is about 2 hours). With a surface emission of 104 to 312 Tg methanol/year (encompasses estimated uncertainty in methanol emissions), the calculation shows that on average, the inclusion of methanol emission produces approximately 1–2% increase in O3, 1–3% decrease in OH, 3–5% increase in HO2, and 3–9% increase in CH2O globally. The maximum perturbation to the oxidants occurs in the tropical upper troposphere. However, the uncertainty associated with current methanol emission estimates produces significantly different model predictions of tropospheric oxidant distributions.

Received 20 February 2003; accepted 14 July 2003; published 4 September 2003.

Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0325 Atmospheric Composition and Structure: Evolution of the atmosphere.

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Citation: Tie, X., A. Guenther, and E. Holland (2003), Biogenic methanol and its impacts on tropospheric oxidants, Geophys. Res. Lett., 30(17), 1881, doi:10.1029/2003GL017167.