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| Titel |
Dust aerosols over India and adjacent continents retrieved using METEOSAT infrared radiance Part I: sources and regional distribution |
| VerfasserIn |
S. Deepshikha, S. K. Satheesh, J. Srinivasan |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 24, no. 1 ; Nr. 24, no. 1 (2006-03-07), S.37-61 |
| Datensatznummer |
250015457
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| Publikation (Nr.) |
 copernicus.org/angeo-24-37-2006.pdf |
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| Zusammenfassung |
| Mineral dust constitutes the single largest contributor
to continental aerosols. To accurately assess the impact of dust aerosols on
climate, the spatial and temporal distribution of dust radiative properties
is essential. Regional characteristics of dust radiative properties,
however, are poorly understood. The magnitude and even sign of dust
radiative forcing is uncertain, as it depends on a number of parameters, such
as vertical distribution of dust, cloud cover and albedo of the underlying
surface. In this paper, infrared radiance (10.5-12.5 µm), acquired from
the METEOSAT-5 satellite ( resolution), was used to retrieve regional
characteristics of dust aerosols for all of 1999. The infrared radiance
depression, due to the presence of dust in the atmosphere, has been
used as an index of dust load, known as the Infrared Difference Dust Index
(IDDI). There have been several studies in the past carried out over the Sahara
using IDDI as a measure of dust load. Over the Indian region, however,
studies on dust aerosols are sparse. Spatial and temporal variability in
dust loading and its regional distribution over various arid and semiarid
regions of India and adjacent continents (0-35° N;
30° E-100° E)
(excluding Sahara) have been studied and the results are examined along with
surface soil conditions (such as vegetation cover and soil moisture).
The advantage of the IDDI method is that information on aerosol properties, such as
chemical composition or microphysical properties, is not needed. A large
day-to-day variation in IDDI was observed over the entire study region, with
values ranging from 4 to 22 K. It was observed that dust activity starts by
March over the Indian deserts, as well as over deserts of the Africa and Arabian
regions. The IDDI reaches maximum during the period of May to August. Regional
maps of IDDI, in conjunction with biomass burning episodes
(using TERRA satellite fire pixel counts), suggest that large IDDI values
observed during the winter months over Northern India could be due to a possible
deposition of black carbon on larger dust aerosols. The IDDI values have
been compared with another year (i.e. 2003), with a large number of dust
storms reported by meteorological departments based on visibility data.
During the dry season, the magnitude of the monthly average IDDI during 2003 was
slightly higher than that of 1999. The monthly mean IDDI was in the range from 4
to 9 K over the Indian deserts, as well as over the deserts of Africa and Arabia. The
maximum IDDI during a month was in the range from 6 to 18 K.
Large IDDI values were observed even over vegetated regions (such as
the vegetated part of Africa and central India), attributed to the presence of
transported dust from nearby deserts. |
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