A narrow zone of low pressure, between the two belts of trade winds, arising from high insolation, especially in the centre of continents in summer; see Quinn and Burt (1967) J. Appl. Met. 6, 6. Also known as the inter-tropical convergence zone, the equatorial trough is not constant in position, breadth, or intensity; see Chao (2000) J. Atmos. Scis 57, 641–51.