Impact of the quasi-biweekly oscillation 1 illation over the western North Pacific on East Asiansubt

• 作 者: 贾小龙 杨崧
• 出 处: 第30届中国气象学会年会
• 发表日期: 2013年6期
• 关键词: quasi-biweekly East Asian summer monsoon South China Sea western Pacific subtrop

　　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 isdivided 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 anorthwestward propagation of convection from equatorial regions to the South China Sea (SCS).The most significant variationsoccur in QBWO phases 3 and4 (enhanced convection over SCS) and phases 7 and 8 (reduced convection over SCS).TheEast Asia Mei-yusignificantly decreases in QBWOphases 3 and 4 butincreasesin phases 7 and 8.The QBWO influences EASMthrough modulating the subtropical monsoon flow and extratropicalcirculation.The response of lower-troposphericatmosphere to QBWO shows a northwestward propagation and a downstream wavetrain that extends northward into the western North Pacific,modulatingthe SCS monsoon trough and the EASM flow associated with moisture transportation.The mid-tropospheric extratropicalcirculation 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 Asianhigh,and these changes contribute toupper-level divergence over subtropical East Asia.