Migrations and dynamics of the intertropical convergence zone
Rainfall on Earth is most intense in the intertropical convergence zone (ITCZ), a narrow belt of clouds centred on average around six degrees north of the Equator. The mean position of the ITCZ north of the Equator arises primarily because the Atlantic Ocean transports energy northward across the Equator, rendering the Northern Hemisphere warmer than the Southern Hemisphere. On seasonal and longer timescales, the ITCZ migrates, typically towards a warming hemisphere but with exceptions, such as during El Niño events. An emerging framework links the ITCZ to the atmospheric energy balance and may account for ITCZ variations on timescales from years to geological epochs.
© 2014 Macmillan Publishers Limited. Received 25 November 2013. Accepted 01 July 2014. Published online 03 September 2014. J. Fasullo and K. Trenberth from the National Center for Atmospheric Research provided the energy flux data we used in Figs 1b and 5 and in some of the estimates in the text. The top-of-atmosphere radiative flux estimates in the text are based on NASA Clouds and the Earth's Radiant Energy System (CERES) data, version CERES EBAF-TOA Ed2.7. S. Marcott provided the temperature reconstructions in Fig. 3, and M. Hell drew Figs 4 and 5. We are grateful for discussions with D. Sigman and N.Meckler and for comments on drafts by F. Ait-Chaalal, A.Donohoe, R. Ferrari, and J.-E. Lee. The research underlying this paper was supported by grants from the US National Science Foundation (numbers AGS-1019211, AGS-1049201 and AGS-1003614).