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| Titel |
Study of MODIS derived AOD at three different locations in the Indo Gangetic Plain: Kanpur, Gandhi College and Nainital |
| VerfasserIn |
P. Choudhry, A. Misra, S. N. Tripathi |
| 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 ; 30, no. 10 ; Nr. 30, no. 10 (2012-10-05), S.1479-1493 |
| Datensatznummer |
250017277
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1479-2012.pdf |
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| Zusammenfassung |
| Moderate resolution imaging spectroradiometer (MODIS) sensors, onboard Terra
and Aqua, have been observing the Earth since start of 2000 and mid 2002,
respectively. The present study provides a comparison of Collection 5
(C005), aerosol optical depth (AOD) retrieved by MODIS, with AERONET-observed AOD over Kanpur (an urban site), Gandhi College (a rural site) and
Nainital (a relatively clean site) in the Indo Gangetic Plain (IGP). The
results show that at Kanpur, MODIS retrievals are well within the prelaunch
uncertainty ± 0.05 ±0.15 τ, and a good correlation (R2 > 0.7
for both Terra and Aqua). Nainital also shows good retrieval (R2 > 0.8
for Terra and R2 > 0.68 for Aqua), as more than 66% of
total collocations are within the prelaunch uncertainty. However, it is seen
that there is significant overestimation in this case, especially in the
months of winter. Gandhi College poses a challenge to MODIS retrieval, as
here <57% of MODIS-retrieved AOD values lay within the prelaunch
uncertainty and the correlation is very poor (R2 ~ 0.5 for Aqua and
R2 ~ 0.4 for Terra); also there is persistent underestimation in
this case. Small value of slope shows that assumed model results in
underestimation, and large intercept values for the linear regression fit
show that errors due to surface reflectance are high here. Our comparison
shows that MODIS retrieval works well over Kanpur, and Nainital with winter
as an exception. However, MODIS retrieval is poor for Gandhi College which
is a rural area. The aerosol properties at Kanpur are currently used as
representative of the entire subcontinent in the MODIS C005 algorithm, which is
not an accurate assumption. The large variability in land use and climate
over India makes it a site too complex for a single aerosol model to be used
over the entire area. Therefore further study with as many sites as possible
over the Indian subcontinent would help provide more realistic modeling for the
Indian subcontinent. |
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