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Trends in the local Hadley and local Walker circulations
Author(s) -
Schwendike Juliane,
Berry Gareth J.,
Reeder Michael J.,
Jakob Christian,
Govekar Pallavi,
Wardle Richard
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2014jd022652
Subject(s) - hadley cell , walker circulation , climatology , circulation (fluid dynamics) , atmospheric circulation , geology , flux (metallurgy) , general circulation model , zonal and meridional , atmospheric sciences , oceanography , climate change , sea surface temperature , physics , materials science , metallurgy , thermodynamics
The linear trend in the local Hadley and Walker circulations from 1979 to 2009 is calculated. These local circulations are defined through a decomposition of the vertical mass flux into its zonal and meridional components. Defining the local circulation this way ensures that the two orthogonal circulations (the local Hadley and Walker circulations) sum to the original circulation even after averaging the circulations regionally. Large regional differences in changes in the local Hadley and Walker circulations over a 31 year period are found. For example, the local Hadley circulation has shifted southward over Africa, the Maritime Continent, and the western and central Pacific by about 1°. Over the Americas and the Atlantic the local Hadley circulation has strengthened by about 1–5%. The zonal component of the vertical mass flux has increased by about 10–20% in the tropics over all continents and decreased over the adjacent oceans by about 10–20%. Although the local Walker circulations in the Indian Ocean and the Atlantic have weakened, the circulation in the Pacific has changed little (about 1–2%). The local Walker circulations in all ocean basins have shifted westward by about 1–2°on average.