A modeling study of Typhoon Nari (2001) at landfall: 2. Structural changes and terrain-induced asymmetries

• Published in: Journal of Geophysical Research Vol. 116; no. D9
• Main Authors: Yang, Ming-Jen, Zhang, Da-Lin, Tang, Xiao-Dong, Zhang, Yi
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 16.05.2011
• Subjects: asymmetry; Atmospheric sciences; Chemistry; Clouds; Evolution; Geophysics; landfall; Physics; terrain; Topography; tropical cyclone; Typhoons
• ISSN: 0148-0227; 2169-897X; 2156-2202; 2169-8996
• DOI: 10.1029/2010JD015445

In this study, a series of model output diagnoses using the cloud‐resolving simulations of Typhoon Nari (2001) with or without Taiwan topography is performed to gain insight into the landfall characteristics of the storm as it moves across Taiwan Island. Various kinematic and precipitation features prior to and after landfall are examined with a focus on the dynamic effects of Taiwan's high topography upon the generation of Nari's asymmetric structures. Results show that tangential winds weaken, whereas the low‐level inflows and midlevel outflows increase, after landfall due to the increased friction and terrain blocking. Meanwhile, the eye wall updrafts exhibit more cellular structures and tend to tilt more outward with height over the high topography. However, Nari's primary and secondary circulations are stronger in the presence of terrain than those without terrain. The radii of the maximum winds and the eye wall updrafts could contract further after landfall, with more pronounced contraction occurring in the portion of the eye wall where more terrain retardation and blocking are present. In particular, the high topography allows the elevated low equivalent potential temperature (θe) air over the rugged terrain to intrude into the inner core region, causing the breakdown of the eye wall. It is concluded that the interaction of Nari's circulations with the elevated low‐θe air, combined with topographical effects, accounts for most of the asymmetrical structures after landfall. Key Points Tangential winds weaken but the low‐level radial inflows increase after landfall Nari primary and secondary circulations are stronger in the presence of terrain High terrain allows the elevated low‐θe air to intrude the inner core