Gulf of Mexico hurricane wave simulations using SWAN: Bulk formula‐based drag coefficient sensitivity for Hurricane Ike

Abstract

[1] The effects of wind input parameterizations on wave estimations under hurricane conditions are examined using the unstructured grid, third-generation wave model, Simulating WAves Nearshore (SWAN). Experiments using Hurricane Ike wind forcing, which impacted the Gulf of Mexico in 2008, illustrate that the default and recommended setting for the wind input parameterization tends to overestimate the maximum significant wave heights in the deep Gulf of Mexico by about 2 m when comparing with observations. The overestimation can be remedied either by adjusting the maximum value of the surface drag coefficient or by substituting a high wind speed formula for the default low to moderate wind speed. Because of added dissipative effects in the shallow coastal areas, the overestimations found in deep water have limited effect on the waves in the near shore shallower waters. Thus, previous wave model results using a low to moderate wind speed bulk formula may still be reliable in waters shallower than about 20-30 m even while overestimating significant wave heights in deeper waters under hurricane conditions.Citation: Huang, Y., R. H. Weisberg, L. Zheng, and M. Zijlema (2013), Gulf of Mexico hurricane wave simulations using SWAN: Bulk formula-based drag coefficient sensitivity for Hurricane Ike,

Wind and Wave Setup Contributions to Extreme Sea Levels at a Tropical High Island: A Stochastic Cyclone Simulation Study for Apia, Samoa

“…The SWAN model predicts the evolution in time and space of the wave action spectrum [23]; here, spectral resolution was as follows: 72 directional bins (5° resolution) and 24 frequency bins, logarithmically spaced between 0.042 and 0.411 Hz. A number of previous studies have shown SWAN's default bulk wind input formulation [24] may overestimate wind drag coefficients (Cd) in tropical cyclone wind conditions [25,26]; Cd is therefore capped at 2.5 m The SWAN model's outer boundaries were the same as the modelling boundaries described in [11], i.e., that of the TC wind fields (Figure 3a). Spatial resolution was set to 5 km, with a 1-km resolution nest centred on the islands of Upolu and Savai'i ( Figure 3b).…”

Exploring Water Level Sensitivity for Metropolitan New York during Sandy (2012) Using Ensemble Storm Surge Simulations

“…Starting at 0000 UTC 25 October, 10-m winds from an earlier WRF-EnKF control forecast were taken every 15 min from the 9-and 3-km WRF domains to derive ADCIRC wind stresses using the Garratt [24] drag formulation without a cap since there is considerable uncertainty in regard to what the actual cap should be (e.g., Weisberg et al [25]). …”

“…Sandy began as a disturbance off the African coast on 11 October 2012 [1], and developed into a major hurricane at 06:00 UTC, 25 October, just south of Cuba.…”

Parameter sensitivity and uncertainty analysis for a storm surge and wave model

“…Further research has demonstrated additional complexity suggesting the wind drag coefficient is also a function of the sea state (Andreas et al, 2012;Reichl et al, 2014) global location and temperature (Kara et al, 2007) and has some dependence on the bottom friction formulation (Johnson and Kofoed-Hansen, 2000;Zijlema et al, 2012). The considerable research that has been applied to estimating the proper wind drag coefficients to reproduce historical hurricanes demonstrates that there is some general agreement on the significance of this model input for accurate surge simulations (Bacopoulos et al, 2012;Cheung et al, 2007;Huang et al, 2013;Vatvani et al, 2012;Zachry et al, 2013).…”