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| Titel |
Evaluation of ozone profile and tropospheric ozone retrievals from GEMS and OMI spectra |
| VerfasserIn |
J. Bak, J. H. Kim, X. Liu, K. Chance, J. Kim |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 2 ; Nr. 6, no. 2 (2013-02-05), S.239-249 |
| Datensatznummer |
250017386
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| Publikation (Nr.) |
 copernicus.org/amt-6-239-2013.pdf |
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| Zusammenfassung |
South Korea is planning to launch the GEMS (Geostationary Environment Monitoring
Spectrometer) instrument into the GeoKOMPSAT (Geostationary Korea
Multi-Purpose SATellite) platform in 2018 to monitor tropospheric air
pollutants on an hourly basis over East Asia. GEMS will measure
backscattered UV radiances covering the 300–500 nm wavelength range with a
spectral resolution of 0.6 nm. The main objective of this study is to
evaluate ozone profiles and stratospheric column ozone amounts retrieved
from simulated GEMS measurements. Ozone Monitoring Instrument (OMI) Level 1B
radiances, which have the spectral range 270–500 nm at spectral resolution
of 0.42–0.63 nm, are used to simulate the GEMS radiances. An optimal
estimation-based ozone profile algorithm is used to retrieve ozone profiles
from simulated GEMS radiances. Firstly, we compare the retrieval
characteristics (including averaging kernels, degrees of freedom for signal,
and retrieval error) derived from the 270–330 nm (OMI) and 300–330 nm (GEMS)
wavelength ranges. This comparison shows that the effect of not using
measurements below 300 nm on retrieval characteristics in the troposphere is
insignificant. However, the stratospheric ozone information in terms of DFS
decreases greatly from OMI to GEMS, by a factor of ∼2. The
number of the independent pieces of information available from GEMS
measurements is estimated to 3 on average in the stratosphere, with
associated retrieval errors of ~1% in stratospheric column
ozone. The difference between OMI and GEMS retrieval characteristics is
apparent for retrieving ozone layers above ~20 km, with a
reduction in the sensitivity and an increase in the retrieval errors for
GEMS. We further investigate whether GEMS can resolve the stratospheric
ozone variation observed from high vertical resolution Earth Observing System (EOS) Microwave Limb
Sounder (MLS). The differences in stratospheric ozone profiles between GEMS
and MLS are comparable to those between OMI and MLS below ~3 hPa (~40 km), except with slightly larger biases and larger
standard deviations by up to 5%. At pressure altitudes above
~3 hPa, GEMS retrievals show strong influence of a priori and
large differences with MLS, which, however, can be sufficiently improved by
using better a priori information. The GEMS-MLS differences show negative
biases of less than 4% for stratospheric column ozone, with standard
deviations of 1–3%, while OMI retrievals show similar agreements with MLS
except for 1% smaller biases at middle and high latitudes.
Based on the comparisons, we conclude that GEMS will measure tropospheric
ozone and stratospheric ozone columns with accuracy comparable to that of
OMI and ozone profiles with slightly worse performance than that of OMI
below ~3 hPa. |
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