Mainz Isoprene Mechanism 2 (MIM2): an isoprene oxidation mechanism for regional and global atmospheric modelling D. Taraborrelli, M. G. Lawrence, T. M. Butler, R. Sander, and J. Lelieveld Max Planck Institute for Chemistry, Atmospheric Chemistry Department, P.O. Box 3060, 55020 Mainz, Germany
Abstract. We present an oxidation mechanism of intermediate size
for isoprene (2-methyl-1,3-butadiene) suitable for simulations in regional
and global atmospheric chemistry models, which we call MIM2. It is a reduction of the corresponding
detailed mechanism in the Master Chemical Mechanism (MCM v3.1) and intended
as the second version of the well-established Mainz Isoprene Mechanism (MIM).
Our aim is to improve the representation of tropospheric
chemistry in regional and global models under all NOx regimes. We evaluate
MIM2 and re-evaluate MIM through comparisons with MCM v3.1.
We find that MIM and MIM2 compute similar O3, OH and isoprene mixing ratios.
Unlike MIM, MIM2 produces small relative biases for NOx and
organic nitrogen-containing species due to a good representation of the alkyl and peroxy acyl nitrates
(RONO2 and RC(O)OONO2). Moreover, MIM2 computes only small relative
biases with respect to hydrogen peroxide (H2O2),
methyl peroxide (CH3OOH), methanol (CH3OH),
formaldehyde (HCHO), peroxy acetyl nitrate (PAN), and formic and acetic acids
(HCOOH and CH3C(O)OH), being always below ≈6% in
all NOx scenarios studied. Most of the isoprene oxidation products are represented
explicitly, including methyl vinyl ketone (MVK), methacrolein (MACR), hydroxyacetone and methyl glyoxal.
MIM2 is mass-conserving with respect to carbon, including CO2 as well.
Therefore, it is suitable for studies assessing carbon monoxide (CO) from biogenic sources,
as well as for studies focused on the carbon cycle.
Compared to MIM, MIM2 considers new species like acetaldehyde (CH3CHO),
propene (CH2=CHCH3) and glyoxal (CHOCHO)
with global chemical production rates for the year 2005 of 7.3, 9.5 and 33.8 Tg/yr, respectively.
Our new mechanism is expected to substantially improve the results
of atmospheric chemistry models by representing many more
intermediates, that are transported and deposited, which allows us to
test model results with many more new measurements.
MIM2 allows regional and global models to easily incorporate new experimental results
on the chemistry of organic species.
Citation: Taraborrelli, D., Lawrence, M. G., Butler, T. M., Sander, R., and Lelieveld, J.: Mainz Isoprene Mechanism 2 (MIM2): an isoprene oxidation mechanism for regional and global atmospheric modelling, Atmos. Chem. Phys., 9, 2751-2777, doi:10.5194/acp-9-2751-2009, 2009.