ANTITRADES

The upper-air winds that blow in some low-latitude areas in the opposite direction to the trade winds, that is, westerly and polewards. The antitrades do not have the same persistence or strength as the surface Trade Winds, tend to be more zonal in flow and are interrupted by other upper-air winds, especially over the continents. In the classical three-cell model of the general circulation of the atmosphere, they are the return flow of the hadley cell. At about 30° latitude they merge into the subtropical jet stream. The antitrades or ‘counter trades’ are replaced during the northern summer by the tropical easterly jet over the northern Indian Ocean and by the African easterly jet over West Africa. Over the Pacific Ocean, the antitrades are subsumed by the walker circulation and el niño-southern oscillation (ENSO) phenomena.