ABSTRACT
Any climate depends on, firstly, local factors and, secondly, advection. The former include radiation, rainfall and evaporation, and the latter the heat and moisture brought by oceans and winds. Winds within 30° of the equator in the Atlantic and Indian oceans were first mapped by Edmund Halley in 1686, and his maps were not superseded till 1855, when Mathew Maury issued charts, based on a recent international exchange of ships’ logs, at a conference in Brussels. Winds at the Intertropical Convergence Zone are commonly light or non-existent, creating maritime calms called the doldrums. The geostrophic wind blows along an isobar, not directly from a place of high pressure to one of low, but at right-angles to the pressure gradient. Hadley circulations are driven chiefly by the solar energy absorbed in the high rate of evaporation from tropical oceans.
