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Narrowing of the ITCZ in a warming climate: Physical mechanisms

Byrne, Michael P. and Schneider, Tapio (2016) Narrowing of the ITCZ in a warming climate: Physical mechanisms. Geophysical Research Letters, 43 (21). pp. 11350-11357. ISSN 0094-8276.

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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.

Item Type:Article
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Schneider, Tapio0000-0001-5687-2287
Additional Information:© 2016 American Geophysical Union. Received 11 JUL 2016; Accepted 14 OCT 2016; Accepted article online 22 OCT 2016; Published online 9 NOV 2016. We thank Paulo Ceppi, Angie Pendergrass, and Robert Wills for helpful discussions. We also thank two anonymous reviewers for their comments and suggestions.
Subject Keywords:ITCZ narrowing; climate change; physical mechanisms; atmospheric energy budget
Record Number:CaltechAUTHORS:20170106-154835521
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Official Citation:Byrne, M. P., and T. Schneider (2016), Narrowing of the ITCZ in a warming climate: Physical mechanisms, Geophys. Res. Lett., 43, 11,350–11,357, doi:10.1002/2016GL070396
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73316
Deposited By: Tony Diaz
Deposited On:07 Jan 2017 00:29
Last Modified:02 Jun 2017 17:31

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