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| Titel |
Validation of MIPAS-ENVISAT NO2 operational data |
| VerfasserIn |
G. Wetzel, A. Bracher, B. Funke, F. Goutail, F. Hendrick, J.-C. Lambert, S. Mikuteit, C. Piccolo, M. Pirre, A. Bazureau, C. Belotti, T. Blumenstock, M. Mazière, H. Fischer, N. Huret, D. Ionov, M. López-Puertas, G. Maucher, H. Oelhaf, J.-P. Pommereau, R. Ruhnke, M. Sinnhuber, G. Stiller, M. Roozendael, G. Zhang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 7, no. 12 ; Nr. 7, no. 12 (2007-06-25), S.3261-3284 |
| Datensatznummer |
250005092
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| Publikation (Nr.) |
 copernicus.org/acp-7-3261-2007.pdf |
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| Zusammenfassung |
| The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)
instrument was launched aboard the environmental satellite ENVISAT into its
sun-synchronous orbit on 1 March 2002. The short-lived species NO2 is
one of the key target products of MIPAS that are operationally retrieved
from limb emission spectra measured in the stratosphere and mesosphere.
Within the MIPAS validation activities, a large number of independent
observations from balloons, satellites and ground-based stations have been
compared to European Space Agency (ESA) version 4.61 operational NO2
data comprising the time period from July 2002 until March 2004 where MIPAS
measured with full spectral resolution. Comparisons between MIPAS and
balloon-borne observations carried out in 2002 and 2003 in the Arctic, at
mid-latitudes, and in the tropics show a very good agreement below 40 km
altitude with a mean deviation of roughly 3%, virtually without any
significant bias. The comparison to ACE satellite observations exhibits only
a small negative bias of MIPAS which appears not to be significant. The
independent satellite instruments HALOE, SAGE II, and POAM III confirm in
common for the spring-summer time period a negative bias of MIPAS in the
Arctic and a positive bias in the Antarctic middle and upper stratosphere
exceeding frequently the combined systematic error limits. In contrast to
the ESA operational processor, the IMK/IAA retrieval code allows accurate
inference of NO2 volume mixing ratios under consideration of all
important non-LTE processes. Large differences between both retrieval
results appear especially at higher altitudes, above about 50 to 55 km.
These differences might be explained at least partly by non-LTE under polar
winter conditions but not at mid-latitudes. Below this altitude region mean
differences between both processors remain within 5% (during night) and
up to 10% (during day) under undisturbed (September 2002) conditions and
up to 40% under perturbed polar night conditions (February and March
2004). The intercomparison of ground-based NDACC observations shows no
significant bias between the FTIR measurements in Kiruna (68° N) and
MIPAS in summer 2003 but larger deviations in autumn and winter. The mean
deviation over the whole comparison period remains within 10%. A mean
negative bias of 15% for MIPAS daytime and 8% for
nighttime
observations has been determined for UV-vis comparisons over Harestua (60° N).
Results of a pole-to-pole comparison of ground-based DOAS/UV-visible
sunrise and MIPAS mid-morning column data has shown that the mean agreement
in 2003 falls within the accuracy limit of the comparison method.
Altogether, it can be indicated that MIPAS NO2 profiles yield valuable
information on the vertical distribution of NO2 in the lower and middle
stratosphere (below about 45 km) during day and night with an overall
accuracy of about 10–20% and a precision of typically 5–15% such that
the data are useful for scientific studies. In cases where extremely high
NO2 occurs in the mesosphere (polar winter) retrieval results in the
lower and middle stratosphere are less accurate than under undisturbed
atmospheric conditions. |
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