This study investigated and quantified the sensitivity of tropical cyclone (TC) wave simulations in the open ocean to different spatial resolutions ( ${1/3}^{\circ }$ , ${1/6}^{\circ }$ , ${1/12}^{\circ }$ and ${1/24}^{\circ }$ ) 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 ( ${1/3}^{\circ }$ ) 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 ${1/3}^{\circ }$ resolution, maximum SWH can be underestimated by as much as 6% in WW3 and 16% in SWAN compared to those with the ${1/24}^{\circ }$ 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.

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.

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.

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.

The impact of weak submeso- to mesoscale SST anomalies on daily averaged trade cumulus cloudiness is investigated using satellite observations that have been validated against shipboard measurements from the Atlantic Tradewind Ocean–Atmosphere Mesoscale Interaction Campaign (ATOMIC). Daily spatial SST anomalies are identified from GOES–POES Blended SST analysis within a 10° × 10° region during January and February 2020. Daily averaged cloud fraction and 10-m neutral wind from satellite observations and reanalysis are composited over the identified SST features, using a common coordinate system based on the near-surface background wind directions. Composites of satellite cloud fraction show a statistically significant increase of cloudiness over the SST warm core with a reduction of cloudiness away from it. These responses are largely the same but with opposite signs over SST cold anomalies, suggesting that spatial heterogeneity in SST can locally imprint on daily cloud fraction. Composites of daily 10-m wind speed and wind convergence anomalies from both satellite and reanalysis show that surface wind speed is increased over SST warm anomalies, implying enhanced turbulence over warmer SSTs. Correspondingly, the surface convergence anomalies in these composites are located around the maximum downwind SST gradient, offset downwind from the cloudiness anomalies. These results indicate that the response of daily cloudiness to these SST anomalies is more likely generated by spatial variability of surface-driven turbulence and surface fluxes rather than that of surface or boundary layer convergence.

This study investigates the local impact of weak sea surface temperature (SST) warm anomalies on trade cumulus cloudiness in an idealized and ensemble framework with large‐eddy simulations. The control experiment uses a spatially uniform, time‐invariant SST and mean large‐scale conditions and atmospheric forcings derived from the Atlantic Tradewind Ocean‐Atmosphere Mesoscale Interaction Campaign. The perturbed experiment adds a Gaussian warm SST anomaly (SSTA) with a 12.5 km radius and 0.5 K magnitude. The ensemble‐averaged differences between perturbation and control experiments show that cloud fraction is enhanced over the downwind half of the prescribed warm SSTA, with the enhancement peaking slightly above the environmental lifting condensation level (LCL) and then decaying with height. Compared to the upper‐level (1.5 km) cloud response, the low‐level cloud response (1 km) to the warm SSTA is stronger and occurs more systematically across different ensemble members. This near‐LCL cloud response is driven by enhanced surface buoyancy flux and buoyancy‐driven turbulence over the warm SSTA as opposed to SSTA‐induced anomalous surface convergence and mesoscale ascent. Process denial experiments indicate that the locally enhanced surface sensible and latent heat fluxes contribute almost equally to increase the near‐LCL cloudiness, even though the locally enhanced surface sensible heat flux plays a dominant role in enhancing surface buoyancy flux. These results corroborate recent satellite composite results (Chen et al., 2023, https://doi.org/10.1175/jas‐d‐23‐0075.1 ), suggesting that the observed increase of daily cloud fraction above warm SSTAs is due to more frequent turbulence‐driven formation of shallow cumuli near the cloud base.