Graphical Abstract

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Feng, T., X.-Q. Yang, L. Wu, R. Huang, and D. Yang, 2020: How do the monsoon trough and the tropical upper-tropospheric trough affect synoptic-scale waves: A comparative study. J. Meteor. Soc. Japan, 98, 735-754.
https://doi.org/10.2151/jmsj.2020-037
Graphical Abstract

Plain Language Summary: As an important precursor for tropical cyclone formation, a conventional synoptic-scale disturbance is usually identified from lower-tropospheric winds over the western North Pacific. However, another type of disturbance with the maximum perturbation in the upper troposphere may be misidentified. Comparing two long-lasting synoptic-scale wave events in 2004 and 2006, the present study showed that the disturbances occurred in the upper troposphere in 2006 while in the lower troposphere in 2004. Such a difference is ascribed to the large-scale background modulated by both the monsoon trough and the tropical upper-tropospheric trough.

Highlights:

• Distinct three-dimensional structures in synoptic-scale disturbances during 2004 and 2006 were investigated.
• Differences in the vertical structure indicated the diverse properties of these disturbances.
• The displacements of the monsoon trough, the tropical upper-tropospheric trough (TUTT), and associated vertical wind shear caused the structural change in these disturbances.