Dust Observations and Climatology - Mineral Dust: A Key Player in the Earth System - page 158

Fig. 7.3 Summary of main dust source areas inferred from satellite observations. Different colours
indicate the three satellite dust products: blue MODIS Deep Blue AOD frequency >40 %, green
OMI AI frequency >40 % and red MSG dust source activation frequency >6%. Contour lines
represent topography and are given at 200 m intervals. The figure illustrates the differences between
the three satellite datasets in terms of identification of dust source regions (except for the Bodélé
Depression) (From Schepanski et al. 2012 )
MODIS dust observations have also been related to land use in order to provide
new estimates of the contribution of anthropogenic dust sources (25 % globally,
8 % in North Africa; Ginoux et al. 2012 ).
Despite the undeniable potential of the satellite approaches for source iden-
tification and characterization, it must be underlined that the interpretation of
individual satellite dust products may be complicated by a number of factors.
The difficulties of interpreting coarse-resolution satellite data and of differentiating
between transported and emitted dust are some of them. In certain cases, the
restriction to clear sky conditions and the contribution of aerosol species other than
dust to the satellite retrieval can be problematic. Schepanski et al. ( 2012 ) compared
Saharan dust source areas observed from three different satellites, the 15-min MSG
IR dust product, daily noontime Aqua MODIS Deep Blue AOD and Aura OMI AI.
Their analysis highlights that differences in temporal resolution are a critical factor
and concludes that different satellite methods lead to the identification of different
source areas (Fig. 7.3 ). Finally, although each satellite dust product has limitations
that must be accounted for in the analysis, observations from space remain one of
the most powerful tools to locate and study dust sources, particular in combination
with numerical models (Huneeus et al. 2012 ; Ginoux et al. 2012 ).
Other satellite datasets may also be applied to global dust source identification.
The MISR/Terra measurements, despite limited temporal coverage (3 or 4 over-