Ship emitted NO2 in the Indian Ocean: comparison of model results with satellite data 1University of Bremen, Institute for Environmental Physics, Bremen, Germany
2Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
3Max Planck Institute for Chemistry, Mainz, Germany
4Centre for Ecology and Hydrology, Wallingford, UK
Received: 25 Jul 2008 – Published in Atmos. Chem. Phys. Discuss.: 21 Aug 2008 – Published: 01 Oct 2009Abstract. The inventory of NOx emission from international shipping has been
evaluated by comparing NO2 tropospheric columns derived from the
satellite instruments SCIAMACHY (January 2003 to February 2008), GOME
(January 1996 to June 2003), and GOME-2 (March 2007 to February 2008) to
NO2 columns calculated with the atmospheric chemistry general
circulation model ECHAM5/MESSy1 (January 2000 to October 2005).
For both measurements and model consistently the tropospheric excess method was used to obtain mean NO2
columns over the shipping lane from India to Indonesia, and over two ship free
regions, the Bay of Bengal and the central Indian Ocean. The long-term data set
from SCIAMACHY yields the first monthly analysis of ship induced NO2
enhancements in the Indian Ocean. Comparison of data from the three instruments
and in addition OMI reveals differences between the datasets which are discussed
with respect to the diurnal cycle of NO2 and the increase in shipping
traffic over the time period studied.
In general, the model
simulates the differences between the regions affected by ship
pollution and ship free regions reasonably well. Minor discrepancies between
model results and satellite data were identified during biomass burning seasons
in March to May over India and the Indochinese Peninsula and August to October
over Indonesia. We conclude that the NOx ship emission inventory used in
this study is a good approximation of NOx ship emissions in
the Indian Ocean for the years 2002 to 2007. It assumes that around
6 Tg(N) yr−1 are emitted by international shipping globally,
resulting in 90 Gg(N) yr−1 in the region of interest when using
Automated Mutual Assistance Vessel Rescue System (AMVER) as spatial
proxy. A second model run using lower ship emissions estimates of
3–4 Tg(N) yr−1 globally results in poorer agreement with the satellite data.
Citation: Franke, K., Richter, A., Bovensmann, H., Eyring, V., Jöckel, P., Hoor, P., and Burrows, J. P.: Ship emitted NO2 in the Indian Ocean: comparison of model results with satellite data, Atmos. Chem. Phys., 9, 7289-7301, doi:10.5194/acp-9-7289-2009, 2009.