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Title: High-Resolution Modeling of Typhoon Morakot (2009): Vortex Rossby Waves and Their Role in Extreme Precipitation over Taiwan

Abstract

A high-resolution nonhydrostatic numerical model, the Advanced Regional Prediction System (ARPS), was utilized to simulate Typhoon Morakot (2009) as it made landfall over Taiwan, producing record rainfall totals. In particular, the mesoscale structure of the typhoon was investigated, emphasizing its associated deep convection, the development of inner rainbands near the center, and the resultant intense rainfall over western Taiwan. Simulations at 15- and 3-km grid spacing revealed that, following the decay of the initial inner eyewall, a new, much larger eyewall developed as the typhoon made landfall over Taiwan. Relatively large-amplitude wave structures developed in the outer eyewall and are identified as vortex Rossby waves (VRWs), due to the wave characteristics and their similarity to VRWs identified in previous studies. Moderate to strong vertical shear over the typhoon system produced a persistent wavenumber-1 (WN1) asymmetric structure during the landfall period, with upward motion and deep convection in the downshear and downshear-left sides, consistent with earlier studies. This strong asymmetry masks the effects of WN1 VRWs. WN2 and WN3 VRWs apparently are associated with the development of deep convective bands in Morakot’s southwestern quadrant. This happens as the waves move cyclonically into the downshear side of the cyclone. Although the typhoonmore » track and topographic enhancement contribute most to the record-breaking rainfall totals, the location of the convective bands, and their interaction with the mountainous terrain of Taiwan, also affect the rainfall distribution. Quantitatively, the 3-km ARPS rainfall forecasts are superior to those obtained from coarser-resolution models.« less

Authors:
 [1];  [2];  [3];  [1]
  1. Univ. of Oklahoma, Norman, OK (United States)
  2. Univ. of Oklahoma, Norman, OK (United States); Center for Analysis and Prediction of Storms, Norman, OK (United States)
  3. Univ. of Oklahoma, Norman, OK (United States); Chinese Academy of Sciences (CAS), Beijing (China)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Org.:
USDOE Office of Science (SC); US Department of the Navy, Office of Naval Research (ONR); National Science Foundation (NSF)
OSTI Identifier:
1565083
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the Atmospheric Sciences
Additional Journal Information:
Journal Volume: 70; Journal Issue: 1; Journal ID: ISSN 0022-4928
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Hurricanes; Waves, atmospheric; Cloud resolving models; Numerical weather prediction/forecasting

Citation Formats

Hall, Jonathan D., Xue, Ming, Ran, Lingkun, and Leslie, Lance M. High-Resolution Modeling of Typhoon Morakot (2009): Vortex Rossby Waves and Their Role in Extreme Precipitation over Taiwan. United States: N. p., 2013. Web. doi:10.1175/jas-d-11-0338.1.
Hall, Jonathan D., Xue, Ming, Ran, Lingkun, & Leslie, Lance M. High-Resolution Modeling of Typhoon Morakot (2009): Vortex Rossby Waves and Their Role in Extreme Precipitation over Taiwan. United States. doi:10.1175/jas-d-11-0338.1.
Hall, Jonathan D., Xue, Ming, Ran, Lingkun, and Leslie, Lance M. Mon . "High-Resolution Modeling of Typhoon Morakot (2009): Vortex Rossby Waves and Their Role in Extreme Precipitation over Taiwan". United States. doi:10.1175/jas-d-11-0338.1. https://www.osti.gov/servlets/purl/1565083.
@article{osti_1565083,
title = {High-Resolution Modeling of Typhoon Morakot (2009): Vortex Rossby Waves and Their Role in Extreme Precipitation over Taiwan},
author = {Hall, Jonathan D. and Xue, Ming and Ran, Lingkun and Leslie, Lance M.},
abstractNote = {A high-resolution nonhydrostatic numerical model, the Advanced Regional Prediction System (ARPS), was utilized to simulate Typhoon Morakot (2009) as it made landfall over Taiwan, producing record rainfall totals. In particular, the mesoscale structure of the typhoon was investigated, emphasizing its associated deep convection, the development of inner rainbands near the center, and the resultant intense rainfall over western Taiwan. Simulations at 15- and 3-km grid spacing revealed that, following the decay of the initial inner eyewall, a new, much larger eyewall developed as the typhoon made landfall over Taiwan. Relatively large-amplitude wave structures developed in the outer eyewall and are identified as vortex Rossby waves (VRWs), due to the wave characteristics and their similarity to VRWs identified in previous studies. Moderate to strong vertical shear over the typhoon system produced a persistent wavenumber-1 (WN1) asymmetric structure during the landfall period, with upward motion and deep convection in the downshear and downshear-left sides, consistent with earlier studies. This strong asymmetry masks the effects of WN1 VRWs. WN2 and WN3 VRWs apparently are associated with the development of deep convective bands in Morakot’s southwestern quadrant. This happens as the waves move cyclonically into the downshear side of the cyclone. Although the typhoon track and topographic enhancement contribute most to the record-breaking rainfall totals, the location of the convective bands, and their interaction with the mountainous terrain of Taiwan, also affect the rainfall distribution. Quantitatively, the 3-km ARPS rainfall forecasts are superior to those obtained from coarser-resolution models.},
doi = {10.1175/jas-d-11-0338.1},
journal = {Journal of the Atmospheric Sciences},
number = 1,
volume = 70,
place = {United States},
year = {2013},
month = {1}
}

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