That's a large swathe of fires in the northern sub Sahara every December. Any explanation for this ? I found the page below which shows a picture month by month

That's a large swathe of fires in the northern sub Sahara every December. Any explanation for this ? I found the page below which shows a picture month by month http://svs.gsfc.nasa.gov/vis/a000000/a003800/a003870/index.html http://svs.gsfc.nasa.gov/vis/a000000/a003800/a003870/index.h... edit: found it at http://www.nasa.gov/mission_pages/fires/main/modis-10-overview.html http://www.nasa.gov/mission_pages/fires/main/modis-10-overvi... "The global fire data show that Africa has more abundant burning than any other continent. MODIS observations have shown that some 70 percent of the world's fires occur in Africa. During a fairly average burning season from July through September 2006, the visualizations show a huge outbreak of savanna fires in Central Africa driven mainly by agricultural activities, but also driven by lightning strikes."