NDLI: Phase locking of equatorial Atlantic variability through the seasonal migration of the ITCZ

Content Provider	Springer Nature Link
Author	Richter, Ingo Xie, Shang Ping Morioka, Yushi Doi, Takeshi Taguchi, Bunmei Behera, Swadhin
Copyright Year	2016
Abstract	The equatorial Atlantic is marked by significant interannual variability in sea-surface temperature (SST) that is phase-locked to late boreal spring and early summer. The role of the atmosphere in this phase locking is examined using observations, reanalysis data, and model output. The results show that equatorial zonal surface wind anomalies, which are a main driver of warm and cold events, typically start decreasing in June, despite SST and sea-level pressure gradient anomalies being at their peak during this month. This behavior is explained by the seasonal northward migration of the intertropical convergence zone (ITCZ) in early summer. The north-equatorial position of the Atlantic ITCZ contributes to the decay of wind anomalies in three ways: (1) horizontal advection associated with the cross-equatorial winds transports air masses of comparatively low zonal momentum anomalies from the southeast toward the equator. (2) The absence of deep convection leads to changes in vertical momentum transport that reduce the equatorial wind anomalies at the surface, while anomalies aloft remain relatively strong. (3) The cross-equatorial flow is associated with increased total wind speed, which increases surface drag and deposit of momentum into the ocean. Previous studies have shown that convection enhances the surface wind response to SST anomalies. The present study indicates that convection also amplifies the surface zonal wind response to sea-level pressure gradients in the western equatorial Atlantic, where SST anomalies are small. This introduces a new element into coupled air-sea interaction of the tropical Atlantic.
Starting Page	3615
Ending Page	3629
Page Count	15
File Format	PDF
ISSN	09307575
Journal	Climate Dynamics
Volume Number	48
Issue Number	11-12
e-ISSN	14320894
Language	English
Publisher	Springer Berlin Heidelberg
Publisher Date	2016-07-28
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Phase locking Atlantic Nino Atlantic zonal mode Interannual variability Air–sea interaction Bjerknes feedback Vertical momentum transport Geophysics/Geodesy Climatology Oceanography
Content Type	Text
Resource Type	Article
Subject	Atmospheric Science

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