Shaohua Chen, Haikun Zhao, Philip J. Klotzbach, Jian Cao, Jia Liang, Weican Zhou, Liguang Wu
{"title":"西北太平洋季风涡度分布是北半球夏季同步尺度波列年际经向移动的潜在驱动力","authors":"Shaohua Chen, Haikun Zhao, Philip J. Klotzbach, Jian Cao, Jia Liang, Weican Zhou, Liguang Wu","doi":"10.1175/jcli-d-23-0672.1","DOIUrl":null,"url":null,"abstract":"Abstract On inter-annual time scales, there is significant meridional migration of the boreal summer (May–October) synoptic-scale wave train (SSW) relative to the summer monsoon trough line over the western North Pacific (WNP) during 1979–2021. The associated plausible physical reasons for the SSW meridional migration are investigated by comparing analyses between two distinct groups: atypical SSW years where SSWs tend to prevail northward of the summer monsoon trough line and typical SSW years where SSWs largely occur along the summer monsoon trough line. During typical SSW years, SSWs originate primarily from equatorial mixed Rossby-gravity (MRG) waves and then develop into off-equatorial tropical depression (TD) waves in the lower troposphere of the monsoon region. During atypical SSW years, SSWs appear to be sourced from upper-level easterlies, propagating downward to the lower troposphere in the monsoon region, with a prevailing TD wave structure. A budget analysis of barotropic eddy kinetic energy suggests that interannual meridional SSW migration is closely related to changes in the vorticity distribution along the summer monsoon trough over the WNP, especially the western part of the summer monsoon trough. These changes cause low-frequency zonal convergence and shear differences, changing barotropic conversion around the monsoon trough and modulating interannual SSW meridional movement. In response to these changes, there are corresponding differences in SSW sources: a predominate MRG-TD wave pattern in typical SSW years and a predominate TD wave pattern in atypical SSW years. These results improve our understanding of the interannual variability of the large-scale circulation and tropical cyclones.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"21 1","pages":""},"PeriodicalIF":4.8000,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Western North Pacific monsoon vorticity distribution as a potential driver of interannual meridional migration of the boreal summer synoptic scale wave train\",\"authors\":\"Shaohua Chen, Haikun Zhao, Philip J. Klotzbach, Jian Cao, Jia Liang, Weican Zhou, Liguang Wu\",\"doi\":\"10.1175/jcli-d-23-0672.1\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Abstract On inter-annual time scales, there is significant meridional migration of the boreal summer (May–October) synoptic-scale wave train (SSW) relative to the summer monsoon trough line over the western North Pacific (WNP) during 1979–2021. The associated plausible physical reasons for the SSW meridional migration are investigated by comparing analyses between two distinct groups: atypical SSW years where SSWs tend to prevail northward of the summer monsoon trough line and typical SSW years where SSWs largely occur along the summer monsoon trough line. During typical SSW years, SSWs originate primarily from equatorial mixed Rossby-gravity (MRG) waves and then develop into off-equatorial tropical depression (TD) waves in the lower troposphere of the monsoon region. During atypical SSW years, SSWs appear to be sourced from upper-level easterlies, propagating downward to the lower troposphere in the monsoon region, with a prevailing TD wave structure. A budget analysis of barotropic eddy kinetic energy suggests that interannual meridional SSW migration is closely related to changes in the vorticity distribution along the summer monsoon trough over the WNP, especially the western part of the summer monsoon trough. These changes cause low-frequency zonal convergence and shear differences, changing barotropic conversion around the monsoon trough and modulating interannual SSW meridional movement. In response to these changes, there are corresponding differences in SSW sources: a predominate MRG-TD wave pattern in typical SSW years and a predominate TD wave pattern in atypical SSW years. 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Western North Pacific monsoon vorticity distribution as a potential driver of interannual meridional migration of the boreal summer synoptic scale wave train
Abstract On inter-annual time scales, there is significant meridional migration of the boreal summer (May–October) synoptic-scale wave train (SSW) relative to the summer monsoon trough line over the western North Pacific (WNP) during 1979–2021. The associated plausible physical reasons for the SSW meridional migration are investigated by comparing analyses between two distinct groups: atypical SSW years where SSWs tend to prevail northward of the summer monsoon trough line and typical SSW years where SSWs largely occur along the summer monsoon trough line. During typical SSW years, SSWs originate primarily from equatorial mixed Rossby-gravity (MRG) waves and then develop into off-equatorial tropical depression (TD) waves in the lower troposphere of the monsoon region. During atypical SSW years, SSWs appear to be sourced from upper-level easterlies, propagating downward to the lower troposphere in the monsoon region, with a prevailing TD wave structure. A budget analysis of barotropic eddy kinetic energy suggests that interannual meridional SSW migration is closely related to changes in the vorticity distribution along the summer monsoon trough over the WNP, especially the western part of the summer monsoon trough. These changes cause low-frequency zonal convergence and shear differences, changing barotropic conversion around the monsoon trough and modulating interannual SSW meridional movement. In response to these changes, there are corresponding differences in SSW sources: a predominate MRG-TD wave pattern in typical SSW years and a predominate TD wave pattern in atypical SSW years. These results improve our understanding of the interannual variability of the large-scale circulation and tropical cyclones.
期刊介绍:
The Journal of Climate (JCLI) (ISSN: 0894-8755; eISSN: 1520-0442) publishes research that advances basic understanding of the dynamics and physics of the climate system on large spatial scales, including variability of the atmosphere, oceans, land surface, and cryosphere; past, present, and projected future changes in the climate system; and climate simulation and prediction.