Identification of surface NO
x
emission sources on a regional scale
using OMI NO
2
I. Zyrichidou
a, *
, M.E. Κoukouli
a
, D. Balis
a
, K. Markakis
b
, A. Poupkou
a
, E. Katragkou
a, c
,
I. Kioutsioukis
d
, D. Melas
a
, K.F. Boersma
e, f
, M. van Roozendael
g
a
Laboratory of Atmospheric Physics, Physics Department, A.U.Th, Thessaloniki, Greece
b
Laboratoire de Meteorologie Dynamique (LMD), IPSL Ecole Polytechnique, Palaiseau Cedex, Paris, France
c
Department of Meteorology and Climatology, School of Geology, Aristotle University of Thessaloniki, Thessaloniki, Greece
d
Laboratory of Atmospheric Physics, Physics Department, University of Patras, Greece
e
Royal Netherlands Meteorological Service, De Bilt, The Netherlands
f
Eindhoven University of Technology, Fluid Dynamics Lab, Eindhoven, The Netherlands
g
Belgian Institute for Space Aeronomy, Brussels, Belgium
highlights
The Balkan a posteriori NO
x
emissions inventory resulted in 1.11 Tg N/y.
Fossil fuel NO
x
emissions over Greece comprise of the 80% of the total emissions.
Soil emissions, omitted in a priori, accounted for 20% of the total over Greece.
Microbial activity emissions are important in high resolution emission inventories.
Biomass burning NO
x
emission rate, accounted for 0.5 10
6
Tg N/km
2
over Greece.
article info
Article history:
Received 13 May 2014
Received in revised form
10 November 2014
Accepted 11 November 2014
Available online 12 November 2014
Keywords:
Nitrogen oxides
Emission inventory
OMI
Inverse modeling
abstract
In this study, an inverse modeling technique is applied to obtain, at a regional scale, top-down emission
estimates for nitrogen oxides utilizing tropospheric nitrogen dioxide (NO
2
) columns retrieved by the
OMI/Aura instrument and estimated by the Comprehensive Air Quality Model with extensions (CAM
x
).
The main idea, applied previously using models with coarse spatial resolution, is to combine the a priori
information from the bottom up emission inventory used in an air quality simulation that covers the
Balkan peninsula in a high resolution grid (0.1
0.1
) with the tropospheric NO
2
quantities estimated
for one complete year by CAM
x
and the tropospheric NO
2
columns retrieved by satellite observations in
order to identify missing emissions sources on a regional scale. The results have identified biases be-
tween the a priori and a posteriori emission inventories due to the missing emission sources or over-
estimation of the spread and quantity of certain emission sources. In such a fine resolution grid we
have also analyzed and considered the horizontal transport on the a posteriori NO
x
emissions. The
deduced a posteriori NO
x
emissions, dominated by the fossil fuel emissions, were found to
be1.11 ± 0.30 Tg N/y, compared to 0.87 ± 0.43 Tg N/y found in the a priori Balkan emission inventory. Soil
emissions over the extended Greek domain, omitted in the a priori inventory, were estimated to account
for almost 20% of the total emitted amount, while for the year 2009 the biomass burning NO
x
emission
flux was also estimated and the average rate accounted for 0.5 10
6
Tg N/km
2
.
© 2014 Elsevier Ltd. All rights reserved.
1. Introduction
One of the major pollutants in the troposphere are nitrogen
oxides (NO
x
¼ NO þ NO
2
). These compounds affect tropospheric
chemistry, air quality and, as a result, climate change (e.g. Shindell
* Corresponding author.
E-mail address: ezyrichi@auth.gr (I. Zyrichidou).
Contents lists available at ScienceDirect
Atmospheric Environment
journal homepage: www.elsevier.com/locate/atmosenv
http://dx.doi.org/10.1016/j.atmosenv.2014.11.023
1352-2310/© 2014 Elsevier Ltd. All rights reserved.
Atmospheric Environment 101 (2015) 82e93