Impact of synthetic space-borne NO<sub>2</sub> observations from the Sentinel-4 and Sentinel-5P missions on tropospheric NO<sub>2</sub> analyses
<p>We present an Observing System Simulation Experiment (OSSE) dedicated to the evaluation of the added value of the Sentinel-4 and Sentinel-5P missions for tropospheric nitrogen dioxide (<span class="inline-formula">NO<sub>2</sub></span>). Sentinel-4 is a geo...
| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/12811/2019/acp-19-12811-2019.pdf |
| Summary: | <p>We present an Observing System Simulation Experiment
(OSSE) dedicated to the evaluation of the added value of the Sentinel-4 and
Sentinel-5P missions for tropospheric nitrogen dioxide (<span class="inline-formula">NO<sub>2</sub></span>). Sentinel-4 is a geostationary (GEO) mission covering the European continent,
providing observations with high temporal resolution (hourly). Sentinel-5P
is a low Earth orbit (LEO) mission providing daily observations with
a global coverage. The OSSE experiment has been carefully designed, with
separate models for the simulation of observations and for the assimilation
experiments and with conservative estimates of the total observation
uncertainties. In the experiment we simulate Sentinel-4 and Sentinel-5P
tropospheric <span class="inline-formula">NO<sub>2</sub></span> columns and surface ozone concentrations at 7 by 7 km
resolution over Europe for two 3-month summer and winter periods. The
synthetic observations are based on a nature run (NR) from a chemistry
transport model (MOCAGE) and error estimates using instrument
characteristics. We assimilate the simulated observations into a chemistry
transport model (LOTOS-EUROS) independent of the NR to evaluate their
impact on modelled <span class="inline-formula">NO<sub>2</sub></span> tropospheric columns and surface concentrations.
The results are compared to an operational system where only ground-based
ozone observations are ingested. Both instruments have an added value to
analysed <span class="inline-formula">NO<sub>2</sub></span> columns and surface values, reflected in decreased biases
and improved correlations. The Sentinel-4 <span class="inline-formula">NO<sub>2</sub></span> observations with hourly
temporal resolution benefit modelled <span class="inline-formula">NO<sub>2</sub></span> analyses throughout the entire
day where the daily Sentinel-5P <span class="inline-formula">NO<sub>2</sub></span> observations have a slightly lower
impact that lasts up to 3–6 h after overpass. The evaluated benefits may
be even higher in reality as the applied error estimates were shown to be
higher than actual errors in the now operational Sentinel-5P <span class="inline-formula">NO<sub>2</sub></span>
products. We show that an accurate representation of the <span class="inline-formula">NO<sub>2</sub></span> profile is
crucial for the benefit of the column observations on surface values. The
results support the need for having a combination of GEO and LEO missions
for <span class="inline-formula">NO<sub>2</sub></span> analyses in view of the complementary benefits of hourly
temporal resolution (GEO, Sentinel-4) and global coverage (LEO, Sentinel-5P).</p> |
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| ISSN: | 1680-7316 1680-7324 |