Extreme Rainfall Mechanisms Exhibited by Typhoon Morakot (2009)

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Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/50358

Title:	Extreme Rainfall Mechanisms Exhibited by Typhoon Morakot (2009)
Authors:	Huang,CY;Wong,CS;Yeh,TC
Contributors:	大氣物理研究所
Keywords:	DATA ASSIMILATION SCHEME;TROPICAL CYCLONE INITIALIZATION;VARIATIONAL DATA ASSIMILATION;ENSEMBLE KALMAN FILTER;ADVANCED RESEARCH WRF;HEAVY RAINFALL;TRACK DEFLECTION;TAIWAN OROGRAPHY;MOUNTAIN-RANGE;BDA SCHEME
Date:	2011
Issue Date:	2012-03-27 17:30:04 (UTC+8)
Publisher:	國立中央大學
Abstract:	Moderate Typhoon Morakot (2009) became the most catastrophic typhoon in Taiwan on record. The MM5 numerical experiments with and without bogus data assimilation (BDA) were used to investigate the extreme rainfall mechanisms in Taiwan associated with the westbound typhoon. The BDA, based on 4DVAR, helps MM5 to maintain a more consolidated typhoon vortex and better predict the observed track after landfall, thus producing realistic extreme rainfall (about 2400 mm) at the southern and Central Mountain Range (CMR) of Taiwan. Severe rainfall in Taiwan is dominated by the CMR that hence modulates rainfall predictability. Model analyses indicate that the synoptic environment provides low-level preconditioning with large convective available energy (CAPE) in the southwest monsoon conveying belt in conjunction with the cyclonic Morakot. When Morakot passed slowly over north Taiwan, the developing Tropical Storm Goni, originating west of Hong Kong, facilitated the moist southwesterly flow to converge with the northerly cyclonic flow of Morakot. These processes contributed to enhanced rainfall in south Taiwan. In an experiment whereby the Goni vortex was initially deactivated by BDA, the southwesterly prevailing flow, southwest of Taiwan, weakened considerably and shifted southward at a later time, resulting in one-third reduction in total accumulated rainfall in south Taiwan. Conversely, total accumulated rainfall in Taiwan is greatly reduced when the initial Morakot vortex is deactivated. Removal of Taiwan topography results in a significant reduction in total accumulated rainfall by more than 50%, due to lack of orographic lift by the CMR.
Relation:	TERRESTRIAL ATMOSPHERIC AND OCEANIC SCIENCES
Appears in Collections:	[Department of Atmospheric Sciences and Graduate Institute of Atmospheric Physics ] journal & Dissertation

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