The diurnal cycle and the meridional extent of the tropics

► Diurnal waves forced by solar heating are trapped equatorially between −30°and 30°. ► These baroclinic waves give rise to the daily tropical meteorology, and intensified mixing. ► The mixing gives rise to the circulation of the Hadley cells and the shape of the tropopause. ► This concept is validated with a forced one-layer model with mixing by breaking waves.