Lightning and the African ITCZ

The idea that tropical lightning activity follows the motion of the Intertropical Convergence Zone (ITCZ) is based on anecdotal evidence, or at best indirect measurements. Definitive observations of lightning from satellite instruments are used here to demonstrate that the seasonal motion of peak lightning over tropical Africa has the same phase as the migration of the ITCZ but that there is no precise space-time coincidence. It is also shown that over shorter time scales the tropical band of lightning activity does not simply follow the Sun nor does it adhere to the ITCZ. What emerges is a complex pattern of behaviour which, though clearly influenced by solar declination and the ITCZ, is also determined by the underlying terrain and humidity. It is sometimes considered that lightning in the tropics would be a good locator of the ITCZ, it is shown here that this is not the case.

► Tropical lightning distribution determined from satellite data.
► ITCZ location determined from pressure and wind reanalysis data.
► Peak tropical lightning is not a good indicator of ITCZ location.