Estimation of the Paris NO<sub><i>x</i></sub> emissions from mobile MAX-DOAS observations and CHIMERE model simulations during the MEGAPOLI campaign using the closed integral method
We determined NO<sub><i>x</i></sub> emissions from Paris in summer 2009 and winter 2009/2010 by applying the closed integral method (CIM) to a large set of car multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements performed within the framework of...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/7853/2017/acp-17-7853-2017.pdf |
| Summary: | We determined NO<sub><i>x</i></sub> emissions from Paris in summer 2009 and winter
2009/2010 by applying the closed integral method (CIM) to a large set of car
multi-axis differential optical absorption spectroscopy (MAX-DOAS)
measurements performed within the framework of the MEGAPOLI project (<a href="http://megapoli.dmi.dk/" target="_blank">http://megapoli.dmi.dk/</a>). MAX-DOAS
measurements of the tropospheric NO<sub>2</sub> vertical column density (VCD) were
performed in large circles around Paris. From the combination of the observed
NO<sub>2</sub> VCDs with wind fields, the NO<sub>2</sub> influx into and the outflux from
the encircled area was determined. The difference between the influx and
outflux represents the total emission. Compared to previous applications of
the CIM, the large number of measurements during the MEGAPOLI campaign
allowed the investigation of important aspects of the CIM. In particular, the
applicability of the CIM under various atmospheric conditions could be
tested. Another important advantage of the measurements during MEGAPOLI is
that simultaneous atmospheric model simulations with a high spatial
resolution (3 × 3 km<sup>2</sup>) are available for all days. Based on
these model data, it was possible to test the consistency of the CIM and to
derive information about favourable or non-favourable conditions for the
application of the CIM. We found that in most situations the uncertainties
and the variability in the wind data dominate the total error budget, which
typically ranges between 30 and 50 %. Also, measurement gaps and
uncertainties in the partitioning ratio between NO and NO<sub>2</sub> are important
error sources. Based on a consistency check, we deduced a set of criteria on
whether measurement conditions are suitable or not for the application of the
CIM. We also developed a method for the calculation of the total error budget
of the derived NO<sub><i>x</i></sub> emissions. Typical errors are between ±30 and
±50 % for individual days (with one full circle around Paris). From
the application of the CIM to car MAX-DOAS observations we derive daily
average NO<sub><i>x</i></sub> emissions for Paris of
4.0 × 10<sup>25</sup> molec s<sup>−1</sup> for summer and of 6.9 × 10<sup>25</sup> molec s<sup>−1</sup> in winter. These values are a factor of about
1.4 and 2.0 larger than the corresponding emissions derived from the
application of the CIM to the model data, using the Toegepast
Natuurwetenschappelijk Onderzoek (TNO) MEGAPOLI emission inventory, in summer and
winter, respectively. Similar ratios (1.5 and 2.3 for summer and winter,
respectively) were found for the comparison with the Monitoring Atmospheric
composition and climate III (MACC-III) emission inventory. The highest
NO<sub><i>x</i></sub> emissions were found during some cold days in February. Enhanced
domestic heating and a reduced conversion efficiency of catalytic converters
might contribute to these enhanced NO<sub><i>x</i></sub> emissions. |
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| ISSN: | 1680-7316 1680-7324 |