TransCom N2O model inter-comparison Part II: Atmospheric inversion estimates of N2O emissions
This study examines N2O emission estimates from
five different atmospheric inversion frameworks based on
chemistry transport models (CTMs). The five frameworks
differ in the choice of CTM, meteorological data, prior uncertainties
and inversion method but use the same prior emissions
and observation data set. The posterior modelled atmospheric
N2O mole fractions are compared to observations to
assess the performance of the inversions and to help diagnose
problems in the modelled transport. Additionally, the
mean emissions for 2006 to 2008 are compared in terms of
the spatial distribution and seasonality. Overall, there is a
good agreement among the inversions for the mean global
total emission, which ranges from 16.1 to 18.7 TgN yr−1
and is consistent with previous estimates. Ocean emissions
represent between 31 and 38% of the global total compared
to widely varying previous estimates of 24 to 38 %.
Emissions from the northern mid- to high latitudes are likely
to be more important, with a consistent shift in emissions
from the tropics and subtropics to the mid- to high latitudes
in the Northern Hemisphere; the emission ratio for 0–30o N
to 30–90o N ranges from 1.5 to 1.9 compared with 2.9 to 3.0
in previous estimates. The largest discrepancies across inversions
are seen for the regions of South and East Asia and
for tropical and South America owing to the poor observational
constraint for these areas and to considerable differences
in the modelled transport, especially inter-hemispheric
exchange rates and tropical convective mixing. Estimates of
the seasonal cycle in N2O emissions are also sensitive to errors
in modelled stratosphere-to-troposphere transport in the
tropics and southern extratropics. Overall, the results show a
convergence in the global and regional emissions compared
to previous independent studies.
THOMPSON R. L.;
ISHIJIMA K.;
SAIKAWA E.;
CORAZZA Matteo;
KARSTENS U.;
PATRA P. K.;
BERGAMASCHI Peter;
CHEVALLIER F.;
DLUGOKENCKY E.;
PRINN R. G.;
WEISS R. F.;
O’DOHERTY S.;
FRASER P. J.;
STEELE L. P.;
KRUMMEL P. B.;
VERMEULEN Alex;
TOHJIMA Y.;
JORDAN A.;
HASZPRA L.;
STEINBACHER M.;
VAN DER LAAN S.;
AALTO T.;
MEINHARDT F.;
POPA M. E.;
MONCRIEFF J.;
BOUSQUET Philippe;
2014-07-08
COPERNICUS GESELLSCHAFT MBH
JRC86457
1680-7316,
www.atmos-chem-phys.net/14/6177/2014/,
https://publications.jrc.ec.europa.eu/repository/handle/JRC86457,
10.5194/acp-14-6177-2014,
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