Contribution of IASI to the observation of the dust aerosol diurnal
cycle over Sahara
Abstract
The Infrared Atmospheric Sounder Interferometer (IASI) is well suited
for monitoring of dust aerosols because of its capability to determine
both AOD and altitude of the dust layer, and because of the good match
between the IASI times of observation (9.30 am and pm, local time) and
the time of occurrence of the main Saharan dust uplift mechanisms. Here,
starting from IASI-derived dust characteristics for an 11-year period,
we assess the capability of IASI to bring realistic information on the
dust diurnal cycle. We first show the morning and nighttime climatology
of IASI-derived dust AOD for two major dust source regions of the
Sahara: The Bodele Depression and the Adrar region. Compared with
simulations from a high resolution model, permitting deep convection to
be explicitly resolved, IASI performs well. In a second step, a Dust
Emission Index specific to IASI is constructed, combining simultaneous
information on dust AOD and mean altitude, with the aim of observing the
main dust emission areas, daytime and nighttime. Comparisons are then
made with other equivalent existing results derived from ground based or
other satellite observations. Results demonstrate the capability of IASI
to improve the documentation of dust distribution over Sahara over a
long period of time. Associating observations of dust aerosols in the
visible, on which a majority of aerosol studies are so far based, and in
the infrared thus appears as a way to complement the results from other
satellite instruments in view of improving our knowledge of their impact
on climate.