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| Titel |
Instantaneous longwave radiative impact of ozone: an application on IASI/MetOp observations |
| VerfasserIn |
S. Doniki, D. Hurtmans, L. Clarisse, C. Clerbaux, H. M. Worden, K. W. Bowman, P.-F. Coheur |
| 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 ; 15, no. 22 ; Nr. 15, no. 22 (2015-11-24), S.12971-12987 |
| Datensatznummer |
250120178
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| Publikation (Nr.) |
 copernicus.org/acp-15-12971-2015.pdf |
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| Zusammenfassung |
| Ozone is an important greenhouse gas in terms of anthropogenic
radiative forcing (RF). RF calculations for ozone were until
recently entirely model based, and significant discrepancies were
reported due to different model characteristics. However, new
instantaneous radiative kernels (IRKs) calculated from hyperspectral
thermal IR satellites have been able to help adjudicate between
different climate model RF calculations. IRKs are defined as the
sensitivity of the outgoing longwave radiation (OLR) flux with
respect to the ozone vertical distribution in the full
9.6 μm band. Previous methods applied to measurements
from the Tropospheric Emission Spectrometer (TES) on Aura rely on
an anisotropy approximation for the angular integration. In this
paper, we present a more accurate but more computationally expensive
method to calculate these kernels. The method of direct integration
is based on similar principles to the anisotropy approximation,
but it deals more precisely with the integration of the Jacobians. We
describe both methods and highlight their differences with respect
to the IRKs and the ozone longwave radiative effect (LWRE), i.e., the
radiative impact in OLR due to absorption by ozone, for both
tropospheric and total columns, from measurements of the Infrared
Atmospheric Sounding Interferometer (IASI) onboard MetOp-A. Biases
between the two methods vary from −25 to +20 % for
the LWRE, depending on the viewing angle. These biases point to the
inadequacy of the anisotropy method, especially at nadir, suggesting
that the TES-derived LWREs are biased low by around 25 % and
that chemistry–climate model OLR biases with respect to TES are
underestimated. In this paper we also exploit the sampling
performance of IASI to obtain first daily global distributions of
the LWRE, for 12 days (the 15th of each month) in 2011, calculated with the
direct integration method. We show that the temporal variation of
global and latitudinal averages of the LWRE shows patterns which are
controlled by changes in the surface temperature and ozone variation
due to specific processes, such as the ozone hole in the polar
regions and stratospheric intrusions into the troposphere. |
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