Graphical Abstract

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Liu, Y. L., C.-Y. Tam, and A. Y. M. Au-Yeung, 2022: Sensitivity of western north Pacific summertime tropical synoptic-scale disturbances to extratropical forcing – A regional climate model study. J. Meteor. Soc. Japan, 100, 167-180.
https://doi.org/10.2151/jmsj.2022-008
Graphical Abstract Published

Plain Language Summary: This study investigates the contribution of extratropical forcing in triggering summertime tropical synoptic-scale disturbances (TSDs) and their later development over the western north Pacific region. When short wave signals from the extratropical region are filtered out, TSD activity, as well as the related rainfall, are both suppressed. Mixed Rossby gravity waves in the equatorial western Pacific area are also weakened due to less wave activity propagated from the north. Further inspection reveals that both the strength as well as coherency of the eddies, over different parts of the TSD wavetrain, can be affected by extratropical forcing in relation to the upper- level westerly pattern.

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Highlights:

• The contribution of the extratropical forcing in the amplitude and characteristics of tropical synoptical-scale disturbances (TSDs) over the western north Pacific is analysed.
• When short waves from the extratropical region are filtered, TSD activity and its related rainfall are suppressed.
• Mixed Rossby gravity waves over the equatorial western Pacific region are also weakened without extratropical forcing.
• Extratropical forcing can influence TSD through the intrusion of wave activity and modulation of background circulation.