Radar Wind Retrieval, Ensemble Simulations, and Cluster Analysis of a Heavy Rainfall Event over Northern Taiwan during 1–2 June 2017

Chieh-Ying Ke aDepartment of Atmospheric Sciences, National Central University, Taoyuan, Taiwan

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Pei-Jung Tsai bCentral Weather Administration, Taipei, Taiwan

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Kao-Shen Chung aDepartment of Atmospheric Sciences, National Central University, Taoyuan, Taiwan

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Yi-Leng Chen cDepartment of Atmospheric Sciences, University of Hawaii at Mānoa, Honolulu, Hawaii, USA

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Yu-Chieng Liou aDepartment of Atmospheric Sciences, National Central University, Taoyuan, Taiwan

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Abstract

This study examines a heavy rainfall event over northern Taiwan from 1–2 June 2017, focusing on the interactions between the marine boundary layer jet (MBLJ), frontal cyclone, and barrier jet (BJ) in influencing rainfall distribution. Three mesoscale convective systems (MCSs) moved eastward, producing intense, prolonged rainfall and transforming the linear convective line from a TS-type (Trailing Stratiform) to a PS-type (Parallel Stratiform) structure. Ensemble simulations, divided into five clusters using k-means clustering with spatial adjustments, reveal distinct rainfall distribution patterns, each linked to specific wind dynamics and mesoscale topographic interactions. Further categorization identified two primary rainfall types: Type A, closely matching the observed event, with substantial inland rainfall driven by a nearby low-pressure center and southwesterly MBLJ; and Type B, with offshore rainfall influenced by a more distant low-pressure center and stronger southerly MBLJ that extends BJs further north. Findings underscore the role of MBLJ, BJ, and cyclone positioning in shaping rainfall distribution, offering insights for more accurate rainfall forecasts in Taiwan’s complex terrain by capturing atmospheric variabilities and informing future forecasting models.

© 2025 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Kao-Shen Chung, kaoshen.chung@gmail.com, kschung@atm.ncu.edu.tw

Abstract

This study examines a heavy rainfall event over northern Taiwan from 1–2 June 2017, focusing on the interactions between the marine boundary layer jet (MBLJ), frontal cyclone, and barrier jet (BJ) in influencing rainfall distribution. Three mesoscale convective systems (MCSs) moved eastward, producing intense, prolonged rainfall and transforming the linear convective line from a TS-type (Trailing Stratiform) to a PS-type (Parallel Stratiform) structure. Ensemble simulations, divided into five clusters using k-means clustering with spatial adjustments, reveal distinct rainfall distribution patterns, each linked to specific wind dynamics and mesoscale topographic interactions. Further categorization identified two primary rainfall types: Type A, closely matching the observed event, with substantial inland rainfall driven by a nearby low-pressure center and southwesterly MBLJ; and Type B, with offshore rainfall influenced by a more distant low-pressure center and stronger southerly MBLJ that extends BJs further north. Findings underscore the role of MBLJ, BJ, and cyclone positioning in shaping rainfall distribution, offering insights for more accurate rainfall forecasts in Taiwan’s complex terrain by capturing atmospheric variabilities and informing future forecasting models.

© 2025 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Kao-Shen Chung, kaoshen.chung@gmail.com, kschung@atm.ncu.edu.tw
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