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Role of seasonal transitions and the westerlies in the interannual variability of the East Asian summer monsoon precipitation

A recent hypothesis holds that changes to the East Asian summer rainfall are characterized by changes in the timing and duration of its intraseasonal stages, controlled by the meridional position of the westerlies relative to the Tibetan Plateau. This hypothesis is examined in the context of the lea...

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Bibliographic Details
Published in:Geophysical research letters 2017-04, Vol.44 (8), p.3788-3795
Main Authors: Chiang, J. C. H., Swenson, L. M., Kong, W.
Format: Article
Language:English
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Summary:A recent hypothesis holds that changes to the East Asian summer rainfall are characterized by changes in the timing and duration of its intraseasonal stages, controlled by the meridional position of the westerlies relative to the Tibetan Plateau. This hypothesis is examined in the context of the leading mode of East Asian summer (July–August) rainfall. One phase of this “tripole” mode—characterized by less rainfall over central eastern China and increased rainfall over northeastern and southeastern China—is tied to an earlier termination of Meiyu that results in a significantly shorter Meiyu and longer Midsummer stage. This phase also exhibits an earlier northward transition of the westerlies to the north of the Plateau, essentially mirroring the changes to precipitation seasonality. The reverse does not hold true for the opposite phase. Our results show direct observational evidence for the meridional position of the westerlies to control East Asian summer monsoon seasonality. Leading mode of July‐August East Asian rainfall variability caused by changes in timing of Meiyu termination and duration of Meiyu/Midsummer Changes to timing and duration associated with variation in the meridional migration of westerlies relative to the Tibetan Plateau Results show direct observational evidence for meridional position of westerlies to control East Asian summer monsoon seasonality
ISSN:0094-8276
1944-8007
DOI:10.1002/2017GL072739