U.S. IOOS coastal and ocean modeling testbed: Evaluation of tide, wave, and hurricane surge response sensitivities to mesh resolution and friction in the Gulf of Mexico

Abstract

[1] This paper investigates model response sensitivities to mesh resolution, topographical details, bottom friction formulations, the interaction of wind waves and circulation, and nonlinear advection on tidal and hurricane surge and wave processes at the basin, shelf, wetland, and coastal channel scales within the Gulf of Mexico. Tides in the Gulf of Mexico are modestly energetic processes, whereas hurricane surge and waves are highly energetic. The unstructured-mesh, coupled wind-wave and circulation modeling system, SWANþADCIRC, is implemented to generate modeled tidal harmonic constituents and hurricane waves and surge for a Hurricane Ike (2008) hindcast. In the open ocean, mesh resolution requirements are less stringent in achieving accurate tidal signals or matching hurricane surge and wave responses; however, coarser resolution or the absence of intertidal zones decreases accuracy along protected nearshore and inland coastal areas due to improper conveyance and/or lateral attenuation. Bottom friction formulations are shown to have little impact on tidal signal accuracy, but hurricane surge is much more sensitive, especially in shelf waters, where development of a strong shore-parallel current is essential to the development of Ike's geostrophic setup. The spatial and temporal contributions of wave radiation stress gradients and nonlinear advection were charted for Ike. Nonlinear advection improves model performance by capturing an additional 10-20 cm of geostrophic setup and increasing resonant cross-shelf waves by 30-40 cm. Wave radiation stress gradients improve performance at coastal stations by adding an extra 20-40 cm to water levels.

Uncertainty in hurricane surge simulation due to land cover specification

“…As a result of the Coastal Inundation Modeling Testbed (COMT), Kerr et al . [] demonstrated the sensitivity of hurricane surge water levels and currents to bottom friction parameters; simulations for Hurricane Ike (2008) with a lower limit on bottom friction (Manning's n of 0.003) reduced water levels by up to 1 m and currents by 1.75 m/s. Although land cover data sets have been extensively used to incorporate bottom friction information to hurricane storm surge models (e.g., the National Land Cover Dataset (NLCD) in Liu et al .…”

Storm Surge Modeling in Large Estuaries: Sensitivity Analyses to Parameters and Physical Processes in the Chesapeake Bay

“…The modeled phase varied around 12-14 degrees in the lower bay, and 30-40 degrees at the upper bay. As Kerr et al (2013) [41] work argues, we found that the harmonic analysis displayed that the astronomical tide phase is less sensitive to mesh resolution and roughness. Similarly to the amplitude, the accuracy of the modeled phase is significantly fair for those stations located in the region "b", and a greater phase lag is observed at the stations located at the region "a", Figure 6 and Table 9.…”

“…In the same study referred previously, Kerr et al (2013) [41] also studied the sensitivity of the storm tide driven by Hurricane Ike to Manning's n bottom friction formulation. They reported that a lower limit on the bottom drag coefficient reduced water levels up to 0.75 m in waterways areas respect to the standard quadratic formulation with no limit, which is used in this work as well.…”

“…The simulations were performed on three levels of roughness and three levels of resolution. [41] have studied the tide amplitude sensitivity to bottom friction formulation (with and without a lower limit on the bottom drag coefficient). They observed that both formulations performed relatively similar, concluding that tidal model is not sensitive to these formulations.…”

“…Conversely, a correct selection in some tributaries is vital to properly simulate storm surge. As Kerr et al (2013) [41] suggested, an adequate simulation of tidal physics is important in storm surge model because they contribute to water levels and currents during hurricanes. Therefore, this study supports the idea to use a moderate value of Manning's n coefficient in James River and a low value in Potomac River.…”