For more information on the Short Wave Infrared Channel, please
GOES 3.9 micron Channel Tutorial
Explanation of images
The lines in the cloud to the northwest of Erika are "ship tracks".
from the ship engines enter the cloud and modify the cloud microphysical
properties. The cloud particles become, in general, smaller in size. This
makes the cloud more reflective, particularly in the 3.9 micron channel
which is very sensitive to particle size. The 3.9 micron channel
radiation arises from thermal emission and reflection of solar energy.
reflection of the solar energy makes the ship tracks appear warmer than the
surrounding cloud (and hence darker in the imagery). The additional cloud
condensation nuclei that emanate from the ship also change the cloud amount,
as observed in a comparison between the ship track and surrounding clouds in
the visible (total reflection) and 11 micron IR images (all thermal emission,
hence cooler signal since less warmer earth radiation is being sensed).
For more information on the Short Wave Infrared Channel, please see the GOES 3.9 micron Channel Tutorial by NOAA/NESDIS/CIRA.