Japan Geoscience Union Meeting 2024

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[E] Poster

A (Atmospheric and Hydrospheric Sciences ) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS04] Extreme Events and Mesoscale Weather: Observations and Modeling

Thu. May 30, 2024 5:15 PM - 6:45 PM Poster Hall (Exhibition Hall 6, Makuhari Messe)

convener:Tetsuya Takemi(Disaster Prevention Research Institute, Kyoto University), Sridhara Nayak(Japan Meteorological Corporation), Satoshi Iizuka(National Research Institute for Earth Science and Disaster Resilience)


5:15 PM - 6:45 PM

[AAS04-P07] A dynamical perspective of the extreme rainfall event over eastern Northeast Brazil in May 2022

*Shunya Koseki1, Isabelle Vilela2, Doris Veleda2, Noel Keenlyside1, Abdou-Lahat Dieng3 (1.Geophysical Institute, University of Bergen, 2.Department of Oceanography, Federal University of Pernambuco, 3.Universite Cheikh Andta de Dakar)

Keywords:Extreme rainfall, Tropical Atlantic, Tropical easterly wave, Northeast Brazil

This study investigated how the extreme rainfall event over eastern Northeast Brazil (ENEB), occurring in the end of May 2022, was induced dynamically using observational and reanalysis data. At monthly time scale, a wet-spell condition is found over the ENEB region in May 2022 indicated by enhanced onshore-ward moisture flux and widely-spreading positive precipitation anomaly. From high-frequency data, the ENEB region experiences continually intense rainy days from May 21st to 28th peaking on May 28th. Focusing on the most intense rainfall event on May 28th, a shallow vortex disturbance of tropical easterly wave can be responsible for this intense event. This easterly wave is initiated over the south tropical Atlantic adjacent to the ENEB region and we indicate that a strong zonal wind shear zone associated with a synoptic-scale high-pressure system generates the vortex as barotropic instability. Even though the vortex centre did not make a landfall over the ENEB region, a part of the vortex band is elongated along the coastal line of ENEB and the vorticity and moisture flux convergence intensify over the coastal ENEB region. The extension and intensification of the vortex band can be indicated by reinforced fluid deformation along the coastal line. The coastal enhancement of vorticity, convergence, and deformation can be interactive, and the sea-land contrast may cause the enhancements due to surface condition change. This study provides a new dynamical insight into the intense precipitation over the ENEB region.