Measurements of total and tropospheric ozone from IASI: comparison with correlative satellite and ozonesonde observations

Abstract

In this paper, we present measurements of total and tropospheric ozone, retrieved from infrared radiance spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI), which was launched on board the MetOp-A European satellite in October 2006. We compare the IASI total ozone columns to observations from the Global Ozone Monitoring Experiment-2 (GOME-2) for one full year of observations (2008). The global distributions are in good agreement, with a correlation coefficient better than 0.9. On average, IASI ozone retrievals exhibit a positive bias compared to GOME-2 of about 4.9 DU (2.9%) to 13 DU (4.4%) depending on the season. In addition to total ozone columns, the good spectral resolution of IASI enables the retrieval of tropospheric ozone concentrations. Comparisons of IASI tropospheric columns to 490 collocated ozone soundings available from several stations around the globe have been performed for the period June 2007–August 2008. IASI tropospheric ozone columns compare well with sonde observations, with correlation coefficients of 0.95 and 0.77 for the [surface – 6 km] and [surface – 12 km] partial columns, respectively. IASI retrievals tend to overestimate the tropospheric ozone columns in comparison with ozonesonde measurements. Positive average biases of 0.15 DU (1.2%) and 3 DU (11%) are found for the [surface – 6 km] and for the [surface – 12 km] partial columns, respectively.

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ACPD
9, 10513–10548, 2009
Measurements of
total and
tropospheric ozone
from IASI
A. Boynard et al.
Title Page
AbstractIntroduction
ConclusionsReferences
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Atmos. Chem. Phys. Discuss., 9, 10513–10548, 2009
www.atmos-chem-phys-discuss.net/9/10513/2009/
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmospheric
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and Physics
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This discussion paper is/has been under review for the journal Atmospheric Chemistry
and Physics (ACP). Please refer to the corresponding final paper in ACP if available.
Measurements of total and tropospheric
ozone from IASI: comparison with
correlative satellite and ozonesonde
observations
A. Boynard1,2, C. Clerbaux1, P.-F. Coheur3, D. Hurtmans3, S. Turquety1,*,
M. George1, J. Hadji-Lazaro1, C. Keim2, and J. Meyer-Arnek4
1UPMC Univ Paris 06, CNRS UMR 8190, Laboratoire Atmosph` eres, Milieux, Observation
Spatiales/IPSL, Paris, France
2Universit´ e Paris 12 et 7, CNRS UMR 7583, Laboratoire Interuniversitaire des Syst` emes
Atmosph´ eriques/IPSL, Cr´ eteil, France
3Spectroscopie de l’Atmosph` ere, Chimie quantique et Photophysique, Universit´ e Libre de
Bruxelles (U.L.B.), Brussels, Belgium
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ACPD
9, 10513–10548, 2009
Measurements of
total and
tropospheric ozone
from IASI
A. Boynard et al.
Title Page
AbstractIntroduction
Conclusions References
TablesFigures
??
??
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4German Aerospace Center (DLR), German Remote Sensing Data Center (DFD),
Oberpfaffenhofen, Wessling, Germany
∗now at: UPMC Univ Paris 06, UMR 8539, Laboratoire de M´ et´ eorologie Dynamique/IPSL,
Paris, France
Received: 24 February 2009 – Accepted: 21 April 2009 – Published: 30 April 2009
Correspondence to: A. Boynard (anne.boynard@latmos.ipsl.fr)
Published by Copernicus Publications on behalf of the European Geosciences Union.
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ACPD
9, 10513–10548, 2009
Measurements of
total and
tropospheric ozone
from IASI
A. Boynard et al.
Title Page
AbstractIntroduction
ConclusionsReferences
TablesFigures
??
??
BackClose
Full Screen / Esc
Printer-friendly Version
Interactive Discussion
Abstract
In this paper, we present measurements of total and tropospheric ozone, retrieved
from infrared radiance spectra recorded by the Infrared Atmospheric Sounding Inter-
ferometer (IASI), which was launched on board the MetOp-A European satellite in
October 2006. We compare the IASI total ozone columns to observations from the
Global Ozone Monitoring Experiment-2 (GOME-2) for one full year of observations
(2008). The global distributions are in good agreement, with a correlation coefficient
better than 0.9. On average, IASI ozone retrievals exhibit a positive bias compared to
GOME-2 of about 4.9DU (2.9%) to 13DU (4.4%) depending on the season. In addi-
tion to total ozone columns, the good spectral resolution of IASI enables the retrieval of
tropospheric ozone concentrations. Comparisons of IASI tropospheric columns to 490
collocated ozone soundings available from several stations around the globe have been
performed for the period June 2007–August 2008. IASI tropospheric ozone columns
compare well with sonde observations, with correlation coefficients of 0.95 and 0.77 for
the [surface – 6km] and [surface – 12km] partial columns, respectively. IASI retrievals
tend to overestimate the tropospheric ozone columns in comparison with ozonesonde
measurements. Positive average biases of 0.15DU (1.2%) and 3DU (11%) are found
for the [surface – 6km] and for the [surface – 12km] partial columns, respectively.
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1Introduction
Global monitoring of ozone (O3) is essential since this molecule plays a key role in the
photo-chemical equilibrium of the atmosphere. In the stratosphere, the ozone layer
has a beneficial role as it absorbs harmful ultraviolet radiation. In contrast, ozone in the
troposphere is considered by air quality agencies as one of the main air pollutants with
significant impact on human health and ecosystems. In addition, ozone is one of the
main greenhouse gases and plays a major role in determining the oxidizing capacity of
the troposphere. For all these reasons, ozone needs to be monitored with good spatial
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ACPD
9, 10513–10548, 2009
Measurements of
total and
tropospheric ozone
from IASI
A. Boynard et al.
Title Page
AbstractIntroduction
Conclusions References
Tables Figures
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??
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and temporal coverage in order to better understand its evolution and its impact on air
quality and climate.
The measurement of tropospheric ozone is best performed by ozonesondes, which
provide vertical profiles from the surface to about 30–35km with a very high vertical
resolution (∼100m) and an accuracy of about 5% in the troposphere. Soundings are
performed at different locations around the globe, collected mainly in the Northern
Hemisphere by the World Ozone and Ultraviolet Data Center (WOUDC). The South-
ern Hemisphere Additional Ozonesondes (SHADOZ) provide additional soundings in
the southern and tropical regions (Thompson et al., 2004), which improve the spa-
tial coverage of the ozonesonde network. However, the coverage remains sparse and
confounds attempts to generate a complete global picture of tropospheric ozone con-
centrations. Despite the difficulty to separate the tropospheric ozone component from
the large stratospheric contribution, satellite measurements are the best way to com-
pliment the ozonesonde observations.
The first distributions of tropospheric ozone were obtained from ultraviolet-visible
(UV-vis) measurements of the Total Ozone Measurement Spectrometer (TOMS) by
subtracting stratospheric ozone from total ozone (Fishman and Larson, 1987; Fishman
et al., 1990). Subsequently, several different residual-based methods have been de-
veloped to derive tropospheric ozone column from TOMS measurements (Ziemke et
al., 1998; Thompson et al., 1999; Chandra et al., 2003). More recently, various ap-
proaches have been used to directly retrieve ozone profiles (and thus to derive tropo-
spheric ozone) from the Global Ozone Monitoring Experiment (GOME) measurements
(Hoogen et al., 1999b; Liu et al., 2005). UV-vis instruments remain by nature, however,
weakly sensitive to the tropospheric ozone content.
Space-borne nadir-viewing instruments using the thermal infrared (TIR) spectral
range to probe the troposphere offer maximum sensitivity in this layer with a vertical res-
olution of about 6km (Coheur et al., 2005; Worden et al., 2007). The first distributions
of total and tropospheric ozone have been retrieved from the Interferometric Monitor
Greenhouse gases (IMG) instrument (Turquety et al., 2002, 2004; Coheur et al., 2005).
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ACPD
9, 10513–10548, 2009
Measurements of
total and
tropospheric ozone
from IASI
A. Boynard et al.
Title Page
AbstractIntroduction
Conclusions References
TablesFigures
??
??
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However, the instrument operated only for 10 months in 1996 on board the Japanese
ADEOS platform. There are currently three nadir viewing TIR instruments providing
ozone measurements from polar-orbiting satellites: the Atmospheric InfraRed Sounder
(AIRS) on AQUA, the Tropospheric Emission Spectrometer (TES) on AURA and the
Infrared Atmospheric Sounding Interferometer (IASI) on MetOp-A. Extended analyses,
using TES and AIRS in particular have highlighted seasonal trends (Divakarla et al.,
2008), enhanced pollution patterns and long-range transport (Zhang et al., 2006; Jour-
dain et al., 2007; Parrington et al., 2008). More recently, the enhanced capabilities
of TIR sounders to probe tropospheric ozone have been used to perform an analy-
sis of the photochemical pollution events that occurred during the 2007 summer heat
wave in Southern Europe, with the recently launched IASI sounder (Eremenko et al.,
2008). The latter study is a first step towards the use of infrared satellite observations
to monitor tropospheric ozone and to improve the forecasts of air quality and climate
models.
In this paper, we present the first global distributions of IASI total ozone columns,
as well as IASI tropospheric ozone measured around several ozonesonde stations.
The next section provides a description of the IASI ozone measurements, including
the characteristics of the instrument and the different ozone products, such as to-
tal columns and vertical profiles. In Sect. 3, the IASI total and tropospheric ozone
columns are compared with correlative ozone measurements, obtained by the GOME-
2 instrument also on board the MetOp-A platform and by ozonesonde data. Section 4
summarizes the study and gives some outlooks.
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2IASI ozone measurements
2.1IASI data
The IASI instrument (Clerbaux et al., 2007) is designed to measure temperature and
moisture profiles with a very high accuracy for numerical weather prediction (Schl¨ ussel
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