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| Titel |
Global distributions, time series and error characterization of atmospheric ammonia (NH3) from IASI satellite observations |
| VerfasserIn |
M. Van Damme, L. Clarisse, C. L. Heald, D. Hurtmans, Y. Ngadi, C. Clerbaux, A. J. Dolman, J. W. Erisman, 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 ; 14, no. 6 ; Nr. 14, no. 6 (2014-03-21), S.2905-2922 |
| Datensatznummer |
250118518
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| Publikation (Nr.) |
 copernicus.org/acp-14-2905-2014.pdf |
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| Zusammenfassung |
| Ammonia (NH3) emissions in the atmosphere have increased substantially
over the past decades, largely because of intensive livestock production and
use of fertilizers. As a short-lived species, NH3 is highly variable in
the atmosphere and its concentration is generally small, except near local
sources. While ground-based measurements are possible, they are challenging
and sparse. Advanced infrared sounders in orbit have recently demonstrated
their capability to measure NH3, offering a new tool to refine global
and regional budgets. In this paper we describe an improved retrieval scheme
of NH3 total columns from the measurements of the Infrared Atmospheric
Sounding Interferometer (IASI). It exploits the hyperspectral character of
this instrument by using an extended spectral range (800–1200 cm−1)
where NH3 is optically active. This scheme consists of the calculation
of a dimensionless spectral index from the IASI level1C radiances, which is
subsequently converted to a total NH3 column using look-up tables built
from forward radiative transfer model simulations. We show how to retrieve
the NH3 total columns from IASI quasi-globally and twice daily above
both land and sea without large computational resources and with an improved
detection limit. The retrieval also includes error characterization of the
retrieved columns. Five years of IASI measurements (1 November 2007 to 31
October 2012) have been processed to acquire the first global and
multiple-year data set of NH3 total columns, which are evaluated and
compared to similar products from other retrieval methods. Spatial
distributions from the five years data set are provided and analyzed at global
and regional scales. In particular, we show the ability of this method to
identify smaller emission sources than those previously reported, as well as
transport patterns over the ocean. The five-year time series is further
examined in terms of seasonality and interannual variability (in particular
as a function of fire activity) separately for the Northern and Southern
Hemispheres. |
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