ITCZ Breakdown and Its Upscale Impact on the Planetary-Scale Circulation over the Eastern Pacific

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dc.contributor.authorYang, Qiu
dc.contributor.authorMajda, A. J.
dc.contributor.authorKhouider, Boualem
dc.date.accessioned2021-03-29T20:32:05Z
dc.date.available2021-03-29T20:32:05Z
dc.date.copyright2017en_US
dc.date.issued2017
dc.description.abstractThe eastern Pacific (EP) intertropical convergence zone (ITCZ) is sometimes observed to break down into several vortices on the synoptic time scale. It is still a challenge for present-day numerical models to simulate the ITCZ breakdown in the baroclinic modes. Also, the upscale impact of the associated mesoscale fluctuations on the planetary-scale circulation is not well understood. Here, a simplified multiscale model for the modulation of the ITCZ is used to study these issues. A prescribed two-scale heating drives the planetary-scale circulation through both planetary-scale mean heating and eddy flux divergence of zonal momentum, where the latter represents the upscale impact of mesoscale disturbances. In an idealized scenario where the heating only varies on the mesoscale, key features of the ITCZ breakdown in the baroclinic modes are captured. The eddy flux divergence of zonal momentum is characterized by midlevel (low level) eastward (westward) momentum forcing at subtropical latitudes of the Northern Hemisphere and opposite-signed midlevel momentum forcing at low latitudes. Such upscale impact of mesoscale fluctuations tends to accelerate (decelerate) planetary-scale zonal jets in the middle (lower) troposphere. Compared with deep heating, shallow heating induces stronger vorticity anomalies on the mesoscale and more significant eddy flux divergence of zonal momentum and acceleration–deceleration effects on the planetary-scale mean flow. In a more realistic scenario where the heating also varies on the planetary scale, the most significant zonal velocity anomalies are confined in the diabatic heating region.en_US
dc.description.reviewstatusRevieweden_US
dc.description.scholarlevelFacultyen_US
dc.identifier.citationYang, Q., Majda, A. J., & Khouider, B. (2017). ITCZ Breakdown and Its Upscale Impact on the Planetary-Scale Circulation over the Eastern Pacific. Journal of the Atmospheric Sciences, 74(12), 4023-4045. https://doi.org/10.1175/JAS-D-17-0021.1en_US
dc.identifier.urihttps://doi.org/10.1175/JAS-D-17-0021.1
dc.identifier.urihttp://hdl.handle.net/1828/12807
dc.language.isoenen_US
dc.publisherJournal of the Atmospheric Sciencesen_US
dc.subjectIntertropical convergence zone
dc.subjectAtmospheric circulation
dc.subjectBaroclinic flows
dc.subjectDeep convection
dc.subjectMeridional overturning circulation
dc.subjectNumerical analysis/modeling
dc.subject.departmentDepartment of Mathematics and Statistics
dc.titleITCZ Breakdown and Its Upscale Impact on the Planetary-Scale Circulation over the Eastern Pacificen_US
dc.typeArticleen_US

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