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| Titel |
The retrieval of aerosol optical depth over land based on time series technique using MSG/SERIVI data |
| VerfasserIn |
Linlu Mei, Yong Xue, Jie Guang, Yingjie Li, Ying Wang, Hui Xu, Chaolin Wu, Leiku Yang, Ziqiang Chen, Xinwei He |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250045653
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| Zusammenfassung |
| In spite of different Aerosol optical depth (AOD) retrieval algorithms have been established
over land for different sensors, most retrievals are limited to twice per day, as by
the morning and afternoon passes of the orbiting polar satellites (Knapp, 2005).
However, aerosol optical properties vary widely and quickly depend on the source
and nature of the aerosol as well as the atmospheric environment, high-frequency
aerosol products are eagerly needed ranged from research to people’s everyday life.
For example, AOD is a significant indicator of dust events, biomass burning, and
many other disasters, which have extreme and time-varying effect on local, or even
global, atmospheric environment. It is important to monitor the temporal aspects of
aerosols.
The Geostationary satellites series has the potential to provide aerosol observations over
land and ocean with multiple observations per day. However, algorithms for polar orbiting
satellites are more mature than geostationary satellites because the spectral channels of the
first generation METEOSAT were rather limited for accurate retrievals of aerosol parameters.
Contrary to traditional geostationary satellite, MSG has three narrow spectral bands in the
solar spectrum (at 0.63, 0.81 and 1.64 μm), in addition to the wide HRV band, and
combines thus somewhat the advantages of a multi-spectral sensor, such as MODIS
and POLODER, with the frequency of METEOSAT measurements (Thieuleux,
2005), which implies that MSG has potential to become a wildly used data source in
meteorology monitoring due to high-temporary and multi-spectral character. Recently there
are some developments on the daily averaged AOD from MSG data. Carrer et al.
(2010) put forwarded daily estimates of aerosol optical thickness over land surface
based on a directional and temporal analysis of SEVIRI MSG visible observations.
Govaerts et al. (2010) developed joint retrieval method of surface reflectance and
aerosol optical depth from MSG/SEVIRI observations with an optimal estimation
approach.
In this paper, we make use of the two solar bands at 0.63 and 0.81 μm of three series time
to retrieve the AOD over land, especially high reflectance area. Follow the analysis of
Chandrasekhar (1960) and Kontratyev (1969); we confined our consideration only to one
approximate method of reducing the problem to solving a set of differential equations in the
application to the case of shortwave radiation transfer. After approximating the exact
integrodifferential equation of radioactive transfer equations for radiant intensity by common
differential equations for the upward and incident radiation fluxes, a MSG/SEVIRI
multi-spectral for three series time algorithm to retrieve AOD and surface reflectance was
proposed following the results from Xue and Cracknell (1995). No other parameters need to
be assumed in our method, which allows the retrieval to be more objective and possibly more
accurate.
The derived AOD is compared to Aerosol Robotic Network (AERONET) observations in
European and African area and a retrieval absolute error was around 0.1 and relative error
was 15% are found.The satellite-derived SEVIRI AOD also compares favourably
with similar MODIS products, which demonstrates a good agreement of the two
results. Although preliminary validation is encouraging, the difference in wavelength
and time differences makes comparison difficult, and further validation is needed. |
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