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| Titel |
A new scheme for sulphur dioxide retrieval from IASI measurements: application to the Eyjafjallajökull eruption of April and May 2010 |
| VerfasserIn |
E. Carboni, R. Grainger, J. Walker, A. Dudhia, R. Siddans |
| 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 ; 12, no. 23 ; Nr. 12, no. 23 (2012-12-03), S.11417-11434 |
| Datensatznummer |
250011638
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| Publikation (Nr.) |
 copernicus.org/acp-12-11417-2012.pdf |
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| Zusammenfassung |
| A new optimal estimation algorithm for the retrieval of sulphur dioxide
(SO2) has been developed for the Infrared Atmospheric Sounding
Interferometer (IASI) using the channels between 1000–1200 and
1300–1410 cm−1. These regions include the two SO2 absorption bands
centred at about 8.7 and 7.3 μm (the ν1 and ν3 bands
respectively). The retrieval assumes a Gaussian SO2 profile and returns
the SO2 column amount in Dobson units and the altitude of the plume in
millibars (mb). Forward modelled spectra (against which the measurements are
compared) are based on the Radiative Transfer for TOVS (RTTOV) code. In our
implementation RTTOV uses atmospheric profiles from European Centre for
Medium-Range Weather Forecasts (ECMWF) meteorological data. The retrieval
includes a comprehensive error budget for every pixel derived from an error
covariance matrix that is based on the SO2-free climatology of the
differences between the IASI and forward modelled spectra. The IASI forward
model includes the ability to simulate a cloud or ash layer in the
atmosphere. This feature is used to illustrate that: (1) the SO2
retrieval is not affected by underlying cloud but is affected if the SO2
is within or below a cloud layer; (2) it is possible to discern if ash (or
other atmospheric constituents not considered in the error covariance matrix)
affects the retrieval using quality control based on the fit of the measured
spectrum by the forward modelled spectrum. In this work, the algorithm is
applied to follow the behaviour of SO2 plumes from the
Eyjafjallajökull eruption during April and May 2010. From 14 April to 4
May (during Phase I and II of the eruption) the total amount of SO2
present in the atmosphere, estimated by IASI measurements, is generally below
0.02 Tg. During the last part of the eruption (Phase III) the values
are an order of magnitude higher, with a maximum of 0.18 Tg measured on the
afternoon of 7 May. |
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