Results of search on satellite image of African dust layer from 26 Feb 2000 
http://www.aoml.noaa.gov/phod/research/docs/PhOD_programs_pg35.pdf
http://earthobservatory.nasa.gov/Features/Dust/

Joe:
Here's a find concerning derechoes, including a nice article on Gustavus Hinrichs, arguably the first state climatologist in US.
Neat.  So he was "... a volatile, abrasive, and sometimes a vindictive man." 
Enjoy.
Ed

http://www.spc.noaa.gov/misc/AbtDerechos/earlyderechopaper.htm

http://www.iacad.org/bios/hinrichs.html
IAS's first Publication
The newspaper clipping to the right was published in the Daily Iowa State Register on Thursday, January 26th, 1876. The article was written by charter member Gustavus Hinrichs and presented at the 'first semi-annual meeting' of the Iowa Academy of Science on January 25th. It is the first public reporting of scientific research presented at an Academy meeting.
http://www.iacad.org/images/earlyias.jpg
Other articles of the day include political commentary, a story about P. T. Barnum reluctantly selling a tiger at auction and a humorous antidote about two Wisconsin girls outwitting a bachelor.