The tragedy of the Air France Airbus crash in or near the Intertropical Convergence Zone (ITCZ) prompted a caller to ask us to explain this weather phenomenon. The ITCZ will appear as a band of clouds near the equator and is easily observed on satellite imagery. This band of clouds may extend for hundreds of miles in places, but will also be broken in to smaller segments as it circles the globe.
The ITCZ follows the sun and will move north during our summer and then further south during the northern hemispheric winter. This movement north and south through the year causes the wet and dry seasons so prevalent in tropical climates. It is referred to as a convergence zone because it is an area where the trade winds come together from both the northern and southern hemispheres. This convergence of the trade winds induces the rising motions that form the thunderstorms that dominate the ITCZ.