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Xuanyu Chen
Graduate School of OceanographyUniversity of Rhode Island Kingston RI USA

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Journal article
Published: 24 July 2020 in Journal of Geophysical Research: Oceans
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This study investigates the impacts of shoaling waves on the wind stress and drag coefficient (C d ) in coastal waters during tropical cyclone (TC) landfall. Numerical experiments are conducted using idealized TCs with two intensities, Category 1 and 5, and two translation speeds, 5 and 10 m/s, propagating toward and normal to the shoreline over two bottom slopes, 1:200 and 1:2000. The wave spectra are simulated using the WAVEWATCH III wave model. The unresolved high‐frequency spectral tail is parameterized as a function of wind speed, and the full wave spectrum is used to calculate the wind stress and drag coefficient. Our results show that the sea state dependence of wind stress magnitude (or C d ) is significantly increased in shallow water at a given wind speed. Compared to its deep‐water value, C d is enhanced in the right (due to shoaling fetch‐dependent waves) and in the left (due to shoaling opposing‐wind swells) TC quadrants. However, C d is reduced in the front/rear quadrants due to weaker wind seas. The misalignment between the wind stress and wind speed directions is enhanced in shallow water. In general, the shoaling wave effects on the wind stress and C d are much stronger on steeper bottom slopes and in faster moving storms.

ACS Style

Xuanyu Chen; Isaac Ginis; Tetsu Hara. Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 2. Tropical Cyclones. Journal of Geophysical Research: Oceans 2020, 125, 1 .

AMA Style

Xuanyu Chen, Isaac Ginis, Tetsu Hara. Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 2. Tropical Cyclones. Journal of Geophysical Research: Oceans. 2020; 125 (7):1.

Chicago/Turabian Style

Xuanyu Chen; Isaac Ginis; Tetsu Hara. 2020. "Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 2. Tropical Cyclones." Journal of Geophysical Research: Oceans 125, no. 7: 1.

Journal article
Published: 24 July 2020 in Journal of Geophysical Research: Oceans
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This study investigates the impact of shoaling wind waves on the drag coefficient in coastal waters. The shoaling wave spectrum is simulated using the WAVEWATCH III (WW3) model with shallow water physics. The high‐frequency part (spectral tail), which is unresolved in the wave model, is empirically parameterized as a function of wind speed. The full wave spectrum is then used to estimate the sea‐state‐dependent wind stress and drag coefficient. Shoaling wind waves are simulated on a sloped bottom under the idealized steady uniform wind. Experimental wind speed spans from 10 to 65 m/s, and the bottom slope is varied from 1:100 to 1:2,000. Our results show that as water depth decreases, the drag coefficient increases gradually to a peak value and then rapidly reduces compared to the deep water value. The maximum C d value occurs roughly where depth‐induced wave breaking starts. The magnitude of C d enhancement is more significant on a steeper slope and can reach 40%. This C d enhancement is mainly due to steepening of waves and reduction of the wave phase speed during the shoaling. Our results also suggest significantly larger variability of C d at a given wind speed in finite‐depth waters than in deep water.

ACS Style

Xuanyu Chen; Tetsu Hara; Isaac Ginis. Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 1. Uniform Wind. Journal of Geophysical Research: Oceans 2020, 125, 1 .

AMA Style

Xuanyu Chen, Tetsu Hara, Isaac Ginis. Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 1. Uniform Wind. Journal of Geophysical Research: Oceans. 2020; 125 (7):1.

Chicago/Turabian Style

Xuanyu Chen; Tetsu Hara; Isaac Ginis. 2020. "Impact of Shoaling Ocean Surface Waves on Wind Stress and Drag Coefficient in Coastal Waters: 1. Uniform Wind." Journal of Geophysical Research: Oceans 125, no. 7: 1.

Journal article
Published: 19 June 2019 in Geosciences
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The southern New England coast of the United States is particularly vulnerable to land-falling hurricanes because of its east-west orientation. The impact of two major hurricanes on the city of Providence (Rhode Island, USA) during the middle decades of the 20th century spurred the construction of the Fox Point Hurricane Barrier (FPHB) to protect the city from storm surge flooding. Although the Rhode Island/Narragansett Bay area has not experienced a major hurricane for several decades, increased coastal development along with potentially increased hurricane activity associated with climate change motivates an assessment of the impacts of a major hurricane on the region. The ocean/estuary response to an extreme hurricane is simulated using a high-resolution implementation of the ADvanced CIRCulation (ADCIRC) model coupled to the Precipitation-Runoff Modeling System (PRMS). The storm surge response in ADCIRC is first verified with a simulation of a historical hurricane that made landfall in southern New England. The storm surge and the hydrological models are then forced with winds and rainfall from a hypothetical hurricane dubbed “Rhody”, which has many of the characteristics of historical storms that have impacted the region. Rhody makes landfall just west of Narragansett Bay, and after passing north of the Bay, executes a loop to the east and the south before making a second landfall. Results are presented for three versions of Rhody, varying in the maximum wind speed at landfall. The storm surge resulting from the strongest Rhody version (weak Saffir–Simpson category five) during the first landfall exceeds 7 m in height in Providence at the north end of the Bay. This exceeds the height of the FPHB, resulting in flooding in Providence. A simulation including river inflow computed from the runoff model indicates that if the Barrier remains closed and its pumps fail (for example, because of a power outage or equipment failure), severe flooding occurs north of the FPHB due to impoundment of the river inflow. These results show that northern Narragansett Bay could be particularly vulnerable to both storm surge and rainfall-driven flooding, especially if the FPHB suffers a power outage. They also demonstrate that, for wind-driven storm surge alone under present sea level conditions, the FPHB will protect Providence for hurricanes less intense than category five.

ACS Style

David S. Ullman; Isaac Ginis; Wenrui Huang; Catherine Nowakowski; Xuanyu Chen; Peter Stempel. Assessing the Multiple Impacts of Extreme Hurricanes in Southern New England, USA. Geosciences 2019, 9, 265 .

AMA Style

David S. Ullman, Isaac Ginis, Wenrui Huang, Catherine Nowakowski, Xuanyu Chen, Peter Stempel. Assessing the Multiple Impacts of Extreme Hurricanes in Southern New England, USA. Geosciences. 2019; 9 (6):265.

Chicago/Turabian Style

David S. Ullman; Isaac Ginis; Wenrui Huang; Catherine Nowakowski; Xuanyu Chen; Peter Stempel. 2019. "Assessing the Multiple Impacts of Extreme Hurricanes in Southern New England, USA." Geosciences 9, no. 6: 265.

Journal article
Published: 11 October 2018 in Journal of Marine Science and Engineering
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This study investigated and quantified the sensitivity of tropical cyclone (TC) wave simulations in the open ocean to different spatial resolutions ( 1 / 3 ∘ , 1 / 6 ∘ , 1 / 12 ∘ and 1 / 24 ∘ ) using two wave models, WAVEWATCH III (WW3) and Simulating WAves Nearshore (SWAN). Six idealized TCs of different radii of maximum winds (25 km and 50 km), and of different translation speeds (3 m/s, 6 m/s and 9 m/s) were prescribed to force these two wave models. Results from both models show that the coarsest resolution ( 1 / 3 ∘ ) introduces significant errors in both the significant wave height (SWH) and the mean wavelength. Moreover, results reveal that sensitivity to spatial resolution strongly depends on storm characteristics. Waves simulated under the small (25 km) and fast moving (9 m/s) TC show the largest sensitivity to the coarse spatial resolutions. With the 1 / 3 ∘ resolution, maximum SWH can be underestimated by as much as 6% in WW3 and 16% in SWAN compared to those with the 1 / 24 ∘ resolution. These findings from the idealized TC simulations are further confirmed by wave simulations under a historical storm. Our analysis also demonstrates that spatial smoothing of the input wind field with coarse grids is not the only reason for the errors in wave simulations.

ACS Style

Xuanyu Chen; Isaac Ginis; Tetsu Hara. Sensitivity of Offshore Tropical Cyclone Wave Simulations to Spatial Resolution in Wave Models. Journal of Marine Science and Engineering 2018, 6, 116 .

AMA Style

Xuanyu Chen, Isaac Ginis, Tetsu Hara. Sensitivity of Offshore Tropical Cyclone Wave Simulations to Spatial Resolution in Wave Models. Journal of Marine Science and Engineering. 2018; 6 (4):116.

Chicago/Turabian Style

Xuanyu Chen; Isaac Ginis; Tetsu Hara. 2018. "Sensitivity of Offshore Tropical Cyclone Wave Simulations to Spatial Resolution in Wave Models." Journal of Marine Science and Engineering 6, no. 4: 116.