Multiple-Scale Interactions during an Extreme Rainfall Event over Southern Vietnam

Document Type : Research Article

Authors

1 Ph.D., Vietnam Institute of Meteorology, Hydrology and Climate Change, Hanoi, Vietnam

2 Instructor, Department of Meteorology and Climate change, Faculty of Meteorology, Hydrology and Oceanography, Hanoi University of Science, Vietnam National University, Hanoi, Vietnam

Abstract

In August 2019, southern Vietnam suffered its worst flooding to date, which was also associated with record-breaking extreme rainfall. This study seeks to explain how this extreme rainfall event can be distinguished from normal rainfall events. The bandpass filter applied to the observed rainfall shows that there were significant intensifications of 3–10-day variation and 11–60-day oscillations during the event. While the latter is characterized by the intensification of westerly flows from the Bay of Bengal to southern Vietnam, the former is related to more complex movements of a series of synoptic-scale disturbances over the western North Pacific. The notion of multiple-scale interactions, inducing the extreme rainfall event is supported by diagnosing the anomalous columnwise moisture divergence over the southern plain region of Vietnam. It is demonstrated that the anomalous convergences associated with the long-term mean moisture and the synoptic-scale moisture transported by the long-term mean flow are the most important factors for formation of the extreme rainfall event.

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References

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Journal of the Earth and Space Physics
Volume 46, Issue 4
February 2021
Pages 259-271

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