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Meteosat RGB Dust Imagery:
Background:
This imagery is created by combining 3 Meteosat IR channels into a single image:
8.7 µm (IR total water/cloud phase/dust band), 10.8 µm (“clean” IR
longwave band) and 12.0 µm (“dirty” IR longwave band). A triple split
window algorithm (12.0-10.8 µm/10.8-8.7 µm/12.0-8.7 µm) is used
to create a single satellite image for detecting atmospheric aerosols.
Uses:
This merged image is centered over North Africa and can be used to detect dust
that is lofted into the atmosphere by African easterly waves (AEWS), mesocale
convective systems (MCSs) and thunderstorm outflow boundaries. Atmospheric
dust is denoted by pink shading in the imagery.
Notes:
• Daytime RGB dust imagery has the best land (blue shading) – dust
(pink shading) aerosol contrast. This is due to changes in surface emissivity
associated with daytime surface heating.
• Nighttime RGB dust imagery has the poorest land (light pink shading)
– dust (pink shading) aerosol contrast. This is due to changes in surface
emissivity associated with nighttime surface cooling.
• Precursors to large dusty SAL outbreaks are often initiated by
passing AEWs and embedded MCSs. Outflow boundaries emanating from the northern
semicircles of MCSs loft dust aerosols into the atmosphere as they move away
from the MCS and over the Sahara Desert.
For more SAL information, please visit the
SAL Background Information
page.
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