Agyakwah, William

Lin, Yuh-Lang

English

North Carolina Agricultural and Technical State University: NC A&T SU Bluford Library's Aggie Digital Collections and Scholarship

North Carolina Agricultural and Technical State University Aggie Digital Collections and Scholarship Spring 2020 Graduate Student Research Symposium Graduate Research Spring 2020 Generation and Enhancement Mechanisms and Essential Ingredients for the Extreme Orographic Rainfall Associated with Typhoon Morakot (2009) Passing over Taiwan’s Central Mountain Range William Agyakwah North Carolina Agricultural and Technical State University Yuh-Lang Lin North Carolina Agricultural and Technical State University Follow this and additional works at: https://digital.library.ncat.edu/gradresearchsymposium20 Recommended Citation Agyakwah, William and Lin, Yuh-Lang, "Generation and Enhancement Mechanisms and Essential Ingredients for the Extreme Orographic Rainfall Associated with Typhoon Morakot (2009) Passing over Taiwan’s Central Mountain Range" (2020). Spring 2020 Graduate Student Research Symposium. 14. https://digital.library.ncat.edu/gradresearchsymposium20/14 This Poster is brought to you for free and open access by the Graduate Research at Aggie Digital Collections and Scholarship. It has been accepted for inclusion in Spring 2020 Graduate Student Research Symposium by an authorized administrator of Aggie Digital Collections and Scholarship. For more information, please contact iyanna@ncat.edu. Generation and Enhancement Mechanisms and Essential Ingredients for the Extreme Orographic Rainfall Associated with Typhoon Morakot (2009) Passing over Taiwan’s Central Mountain RangeSpring 2020 N.C. A&T Graduate Research SymposiumSponsored by the Graduate College and the Graduate Student Advisory CouncilINTRODUCTIONMETHODOLOGY• REAL CASE SIMULATION• ARW-WRF Model V3.3.1 • Initialized by NCEP Global Forecast System (GFS) Data• Daily data (00Z) from Aug 03 – 10, 2009• Grid Dimensions:• Nested grid (27, 9, 3 km)• 28 stretched vertical levels• Physics Parameterization Schemes:• Microphysics – Goddard• Cumulus parameterization – Kain-Fritsch• PBL – YSU• Surface layer – Monin-Obukov • Longwave – RRTM• Shortwave – Dudhia• Observed Data:• Typhoon best track data from Japan Meteorological Agency (JMA)RESULTS – VERIFICATION OF CONTROL (CTL) CASE RESULTS – VERTICAL CROSS-SECTION & CONCEPTUAL MODELFig. 2. (a) Best track data from JMA compared with WRF simulated track data for the period of Aug 5, 00Z to Aug 10, 00Z.(b) Maximum wind speed and (c) minimum sea level pressure (MSLP) data from JMA are compared with WRF simulateddata for the period of Aug 3, 06Z to Aug 10, 00ZRESULTS – OROGRAPHIC RAIN INGREDIENTS  (b)(c)(a)a) The WRF simulated max rainfall is8% lower than the observed value of1402 mm.b) Since the simulated results comparedwell with the observed data, it assuresus to use the simulated results toexamine the essential orographic rainingredients, and the generation andenhancement mechanisms related toTyphoon Morakot (2009).CONCLUSIONSa) The orographically initiated convection in SW CMR was able to develop further andproduced heavier rainfall than in the NE CMR.b) The increase of strong, moist, unstable flow associated with the TC rainband impingingon the southwest CMR steep terrain possesses enough key ingredients for producingheavy rainfall.c) When the TC convection merged with the orographically initiated convection, theorographic rainfall was decreased, mainly due to the destruction of Morakot’s structure.d) Strong downslope winds and gravity waves help cut off rainfall on the lee slope.ACKNOWLEDGEMENTSThe authors would like to acknowledge Drs. Jing Zhang, Ademe Mekonnen, and Liping Liuat North Carolina A&T State University for their insightful discussions and comments onthis research. This research was supported by the National Science Foundation AwardAGS-1265783 and NCAR Diversity Fund. The authors would like to acknowledge NCARand CISL for their support of computing time on the Cheyenne supercomputer (Project No.UNCS0030)Corresponding E-mail Addresses:  Dr. Yuh-Lang Lin    – ylin@ncat.eduWilliam Agyakwah  – wagyakwa@aggies.ncat.eduFig. 6: A conceptual model showing four keyprocesses associated with the generation andenhancement of orographic TC rain over thesouthwest of CMR during the passage of typhoonMorakot (2009).Fig. 5. Vertical cross-section i (24.3oN) and accumulated rainfall along thecross-section (08/07/03 – 08/08/00Z).a) Orographic rain was initiated by terrainon 8/7/03Z because typhoon center wasabout 300km away from the CMR(shown by the blue line).b) Rainfall steadily increased and maxrain of 140mm occurred on 8/7/21Z; asshown by the red line. The second curve(red line) is the rain related to theeyewall.c) The enhancement was due to themerging of orographic initiated rain andtropical cyclone (TC) rain.d) Damage of typhoon’s structure andweakening of its convection declined therainfall on 8/8/00ZFig. 1. Domain configuration for TyphoonMorakot simulations with three domains of27km (d01), 9km (d02), and 3km (d03) gridresolutions.Fig. 3. Comparison of 24hr accumulated rainfall for (a) observ-ation and (b) WRF simulated fields during 8/8/00Z – 8/9/00Z.• It has been shown that several heavy orographic rainfallcases that occurred during the passage of typhoons overTaiwan’s Central Mountain Range (CMR) are closelyrelated to some common ingredients (e.g. Yang andChing 2005; Witcraft et al. 2005; Yang et al. 2008;).• Several studies have been done on typhoon Morakot(2009) about general factors responsible for the extremelyheavy rainfall (e.g. C.-Y. Lin et al. 2010; Yu and Chen,2013; Huang and Lin, 2014) but, less is known about thegeneration and enhancement mechanisms.• Lin et al. (2001), extended Doswell et al.'s (1996)ingredient argument, in which the orographic precipitation(P) is determined by the following equation:a) Southwest monsoonal (SWM) current initiatedorographic rainfall.b) Northwest rainband (RB) moved in while typhoonapproached northeast CMR.c) Southwest monsoonal current and northwest rainbandmerged into a very moist LLJ with preexisting convection.d) Orographic rain and TC rain merged and led toenhanced convection which produced extreme rainfallAuthors: William Agyakwah1, Yuh-Lang Lin1,21Applied Science & Technology PhD Program, 2Department of PhysicsNorth Carolina A&T State UniversityProgram: Applied Science & Technology (PhD)Advisor: Dr. Yuh-Lang Lin𝐏 = 𝑬𝝆𝒂𝝆𝒘𝒘𝒐𝒓𝒐+ 𝒘𝒆𝒏𝒗 𝒒𝒗𝑳𝒔𝑪𝒔

Generation and Enhancement Mechanisms and Essential Ingredients for the Extreme Orographic Rainfall Associated with Typhoon Morakot (2009) Passing over Taiwan’s Central Mountain Range

https://digital.library.ncat.edu/cgi/viewcontent.cgi?article=1001&amp;context=gradresearchsymposium20

Generation and Enhancement Mechanisms and Essential Ingredients for the Extreme Orographic Rainfall Associated with Typhoon Morakot (2009) Passing over Taiwan’s Central Mountain Range

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