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Impact of the quasi‐biweekly oscillation over the western North Pacific on East Asian subtropical monsoon during early summer
Author(s) -
Jia Xiaolong,
Yang Song
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/jgrd.50422
Subject(s) - climatology , subtropics , subtropical ridge , troposphere , monsoon , rossby wave , east asian monsoon , geology , empirical orthogonal functions , extratropical cyclone , east asia , atmospheric circulation , trough (economics) , oceanography , environmental science , atmospheric sciences , precipitation , geography , china , meteorology , macroeconomics , archaeology , fishery , economics , biology
The impact of quasi‐biweekly oscillation (QBWO) over the western North Pacific on East Asian summer monsoon (EASM) is investigated. The life cycle of QBWO is divided into eight phases defined by the two leading principal components (PC1 and PC2) of an empirical orthogonal function analysis. Subtropical rainfall shows significant changes, with a northwestward propagation of convection from equatorial regions to the South China Sea (SCS). The most significant variations occur in QBWO phases 3 and 4 (enhanced convection over SCS) and phases 7 and 8 (reduced convection over SCS). The East Asia Mei‐yu significantly decreases in QBWO phases 3 and 4 but increases in phases 7 and 8. The QBWO influences EASM through modulating the subtropical monsoon flow and extratropical circulation. The response of lower tropospheric atmosphere to QBWO shows a northwestward propagation and a downstream wave train that extends northward into the western North Pacific, modulating the SCS monsoon trough and the EASM flow associated with moisture transportation. The mid‐tropospheric extratropical circulation and the western Pacific subtropical high also show obvious changes accompanying QBWO evolution, resulting in circulation patterns associated with cold air activity. Moreover, changes with QBWO are found in the upper tropospheric East Asian westerly jet stream and the South Asian high, and these changes contribute to upper level divergence over subtropical East Asia.