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Seasonal and Interannual Variations of the Energy Flux Equator and ITCZ. Part II: Zonally Varying Shifts of the ITCZ

Adam, Ori and Bischoff, Tobias and Schneider, Tapio (2016) Seasonal and Interannual Variations of the Energy Flux Equator and ITCZ. Part II: Zonally Varying Shifts of the ITCZ. Journal of Climate, 29 (20). pp. 7281-7293. ISSN 0894-8755. http://resolver.caltech.edu/CaltechAUTHORS:20160930-151837626

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Abstract

The ITCZ lies at the ascending branch of the tropical meridional overturning circulation, where near-surface meridional mass fluxes vanish. Near the ITCZ, column-integrated energy fluxes vanish, forming an atmospheric energy flux equator (EFE). This paper extends existing approximations relating the ITCZ position and EFE to the atmospheric energy budget by allowing for zonal variations. The resulting relations are tested using reanalysis data for 1979–2014. The zonally varying EFE is found as the latitude where the meridional component of the divergent atmospheric energy transport (AET) vanishes. A Taylor expansion of the AET around the equator relates the ITCZ position to derivatives of the AET. To a first order, the ITCZ position is proportional to the divergent AET across the equator; it is inversely proportional to the local atmospheric net energy input (NEI) that consists of the net energy fluxes at the surface, at the top of the atmosphere, and zonally across longitudes. The first-order approximation captures the seasonal migrations of the ITCZ in the African, Asian, and Atlantic sectors. In the eastern Pacific, a third-order approximation captures the bifurcation from single- to double-ITCZ states that occurs during boreal spring. In contrast to linear EFE theory, during boreal winter in the eastern Pacific, northward cross-equatorial AET goes along with an ITCZ north of the equator. EFE and ITCZ variations driven by ENSO are characterized by an equatorward (poleward) shift in the Pacific during El Niño (La Niña) episodes, which are associated with variations in equatorial ocean energy uptake.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1175/JCLI-D-15-0710.1DOIArticle
http://journals.ametsoc.org/doi/10.1175/JCLI-D-15-0710.1PublisherArticle
ORCID:
AuthorORCID
Schneider, Tapio0000-0001-5687-2287
Additional Information:© 2016 American Meteorological Society. Manuscript received 6 October 2015, in final form 13 July 2016. We thank Momme Hell for his visualization advice.
Subject Keywords:Circulation/ Dynamics; Atmosphere-ocean interaction; Atmospheric circulation; ENSO; Meridional overturning circulation; Physical Meteorology and Climatology; Energy budget/balance
Record Number:CaltechAUTHORS:20160930-151837626
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160930-151837626
Official Citation:Ori Adam, Tobias Bischoff, and Tapio Schneider, 2016: Seasonal and Interannual Variations of the Energy Flux Equator and ITCZ. Part II: Zonally Varying Shifts of the ITCZ. J. Climate, 29, 7281–7293, doi: 10.1175/JCLI-D-15-0710.1.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70725
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:30 Sep 2016 22:37
Last Modified:30 Sep 2016 22:37

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