Abstract
Abstract. This paper details and tests numerical improvements to the ADvanced CIRCulation (ADCIRC) model, a widely used finite-element method shallow-water equation solver, to more accurately and efficiently model global storm tides with seamless local mesh refinement in storm landfall locations. The sensitivity to global unstructured mesh design was investigated using automatically generated triangular meshes with a global minimum element size (MinEle) that ranged from 1.5 to 6 km. We demonstrate that refining resolution based on topographic seabed gradients and employing a MinEle less than 3 km are important for the global accuracy of the simulated astronomical tide. Our recommended global mesh design (MinEle = 1.5 km) based on these results was locally refined down to two separate MinEle values (500 and 150 m) at the coastal landfall locations of two intense storms (Hurricane Katrina and Super Typhoon Haiyan) to demonstrate the model's capability for coastal storm tide simulations and to test the sensitivity to local mesh refinement. Simulated maximum storm tide elevations closely follow the lower envelope of observed high-water marks (HWMs) measured near the coast. In general, peak storm tide elevations along the open coast are decreased, and the timing of the peak occurs later with local coastal mesh refinement. However, this mesh refinement only has a significant positive impact on HWM errors in straits and inlets narrower than the MinEle and in bays and lakes separated from the ocean by these passages. Lastly, we demonstrate that the computational performance of the new numerical treatment is 1 to 2 orders of magnitude faster than studies using previous ADCIRC versions because gravity-wave-based stability constraints are removed, allowing for larger computational time steps.
Highlights
Extreme coastal sea levels and flooding driven by storms and tsunamis can be accurately modeled by the shallow-water equations (SWEs)
The ADvanced CIRCulation (ADCIRC) storm tide model used in this study is an finiteelement methods (FEMs) solver that has been extensively used for detailed hurricane inundation studies at local and regional scales (e.g., Westerink et al, 2008; Bunya et al, 2010; Hope et al, 2013), as well as for an operational storm tide forecast model run by the US National Oceanic and Atmospheric Administration (NOAA) (Funakoshi et al, 2011; Vinogradov et al, 2017)
M2 amphidromes in the high-latitude regions are largely corrected such that any disparities between TPXO9Atlas and our updated model solutions are qualitatively hard to discern from a global perspective (Fig. 5)
Summary
Extreme coastal sea levels and flooding driven by storms and tsunamis can be accurately modeled by the shallow-water equations (SWEs). The SWEs are often numerically solved by discretizing the continuous equations using unstructured meshes with either finite-volume methods (FVMs) or finiteelement methods (FEMs). These unstructured meshes can efficiently model the large range in length scales associated with physical processes that occur in the deep ocean to the nearshore region (e.g., Chen et al, 2003; Westerink et al, 2008; Zhang et al, 2016; Le Bars et al, 2016; Fringer et al, 2019), many difficulties for large-scale ocean general circulation modeling remain (Danilov, 2013). The orthogonal requirement makes mesh generation over wide areas with fractal
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