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Local partitioning of the overturning circulation in the tropics and the connection to the Hadley and Walker circulations
Author(s) -
Schwendike Juliane,
Govekar Pallavi,
Reeder Michael J.,
Wardle Richard,
Berry Gareth J.,
Jakob Christian
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd020742
Subject(s) - hadley cell , walker circulation , circulation (fluid dynamics) , climatology , partition (number theory) , atmospheric circulation , zonal and meridional , general circulation model , geology , secondary circulation , atmospheric sciences , meteorology , environmental science , el niño southern oscillation , geography , mathematics , physics , climate change , oceanography , mechanics , combinatorics
Conceptually, it is useful to partition the three‐dimensional tropical circulation into meridional and zonal components, namely, the Hadley and Walker circulations. The averaging involved in their definitions can introduce ambiguities. These problems can be circumvented by first partitioning the total vertical mass flux into components associated with overturning in the meridional and zonal directions, respectively, called here the local Hadley and local Walker circulations. Defining the local Hadley and local Walker circulations this way ensures the pair of two‐dimensional overturning circulations can be added to give the original three‐dimensional circulation, even when the averages are taken over limited domains. The method is applied to the vertical motion from the ERA‐Interim reanalysis for the period 1979 to 2009. One important result is that the local Hadley circulation responds much more strongly to ENSO than the local Walker circulation, even though the local Walker circulation in the central Pacific weakens during El Niño years and strengthens and widens during La Niña years.