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| Titel |
Recent variability of the solar spectral irradiance and its impact on climate modelling |
| VerfasserIn |
I. Ermolli, K. Matthes, T. Dudok de Wit, N. A. Krivova, K. Tourpali, M. Weber, Y. C. Unruh, L. Gray, U. Langematz, P. Pilewskie, E. Rozanov, W. Schmutz, A. Shapiro, S. K. Solanki, T. N. Woods |
| 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 ; 13, no. 8 ; Nr. 13, no. 8 (2013-04-17), S.3945-3977 |
| Datensatznummer |
250018591
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| Publikation (Nr.) |
 copernicus.org/acp-13-3945-2013.pdf |
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| Zusammenfassung |
The lack of long and reliable time series of solar spectral irradiance (SSI)
measurements makes an accurate quantification of solar contributions to
recent climate change difficult. Whereas earlier SSI observations and models
provided a qualitatively consistent picture of the SSI variability, recent
measurements by the SORCE (SOlar Radiation and Climate Experiment) satellite suggest a significantly stronger
variability in the ultraviolet (UV) spectral range and changes in the visible
and near-infrared (NIR) bands in anti-phase with the solar cycle. A number of
recent chemistry-climate model (CCM) simulations have shown that this might
have significant implications on the Earth's atmosphere. Motivated by these
results, we summarize here our current knowledge of SSI variability and its
impact on Earth's climate.
We present a detailed overview of existing SSI measurements and provide
thorough comparison of models available to date. SSI changes influence the
Earth's atmosphere, both directly, through changes in shortwave (SW) heating
and therefore, temperature and ozone distributions in the stratosphere, and
indirectly, through dynamical feedbacks. We investigate these direct and
indirect effects using several state-of-the art CCM simulations forced with
measured and modelled SSI changes. A unique asset of this study is the use of
a common comprehensive approach for an issue that is usually addressed
separately by different communities.
We show that the SORCE measurements are difficult to reconcile with earlier
observations and with SSI models. Of the five SSI models discussed here,
specifically NRLSSI (Naval Research Laboratory Solar Spectral Irradiance),
SATIRE-S (Spectral And Total Irradiance REconstructions for the Satellite era),
COSI (COde for Solar Irradiance), SRPM (Solar Radiation Physical Modelling), and
OAR (Osservatorio Astronomico di Roma), only one shows a
behaviour of the UV and visible irradiance qualitatively resembling that of
the recent SORCE measurements. However, the integral of the SSI computed with
this model over the entire spectral range does not reproduce the measured
cyclical changes of the total solar irradiance, which is an essential
requisite for realistic evaluations of solar effects on the Earth's climate
in CCMs.
We show that within the range provided by the recent SSI observations and
semi-empirical models discussed here, the NRLSSI model and SORCE observations
represent the lower and upper limits in the magnitude of the SSI solar cycle
variation.
The results of the CCM simulations, forced with the SSI solar cycle
variations estimated from the NRLSSI model and from SORCE measurements, show
that the direct solar response in the stratosphere is larger for the SORCE
than for the NRLSSI data. Correspondingly, larger UV forcing also leads to a
larger surface response.
Finally, we discuss the reliability of the available data and we propose
additional coordinated work, first to build composite SSI data sets out of
scattered observations and to refine current SSI models, and second, to run
coordinated CCM experiments. |
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