Narrowing of the ITCZ in a warming climate: physical mechanisms

Michael P. Byrne, Tapio Schneider

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61 Citations (Scopus)


The Intertropical Convergence Zone (ITCZ) narrows in response to global warming in both observations and climate models. However, a physical understanding of this narrowing is lacking. Here we show that the narrowing of the ITCZ in simulations of future climate is related to changes in the moist static energy (MSE) budget. MSE advection by the mean circulation and MSE divergence by transient eddies tend to narrow the ITCZ, while changes in net energy input to the atmosphere and the gross moist stability tend to widen the ITCZ. The narrowing tendency arises because the meridional MSE gradient strengthens with warming, whereas the largest widening tendency is due to increasing shortwave heating of the atmosphere. The magnitude of the ITCZ narrowing depends strongly on the gross moist stability and clouds, emphasizing the need to better understand these fundamental processes in the tropical atmosphere.
Original languageEnglish
Pages (from-to)11350-11357
Number of pages8
JournalGeophysical Research Letters
Issue number21
Early online date9 Nov 2016
Publication statusPublished - 16 Nov 2016


  • ITCZ narrowing
  • Climate change
  • Physical mechanisms
  • Atmospheric energy budget


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