Figure: HBL model simulated maximum wind swath for Hurricane Florence over land. The colored markers over land represent the differences of maximum sustained wind speed between HBL simulated wind and observed wind. The color bar on the left-hand side represents the magnitude (m/s) of HBL simulated maximum sustained wind speed and color bar on the right-hand side represents the magnitude (m/s) of errors between model and observations shown as colored markers over land. Track of Hurricane Florence is shown in the black colored line.
Building upon existing models, partnerships, and expertise, this project advances model capabilities and develops a real-time hazard and impact prediction system for hurricanes and nor'easters in Southern New England. The major goal of this project is to comprehensively investigate hazards and impacts in the focus regions using the most advanced coupled atmospheric, coastal ocean circulation/storm surge, wave and hydrological models and transition the developed new modeling capabilities to the real-time ADCIRC-Surge Guidance System (ASGS).
In addition to storm surge, landfalling hurricanes and extratropical storms often cause extreme rainfall runoff and floods in coastal rivers, extreme waves during the hurricane often cause severe erosion in beaches and coastal roadways, and strong wave forces can cause damage to coastal and waterfront structures. Our innovative modeling approach seeks to understand the consequences of the combined coastal and inland flooding that has not been previously considered. Southern New England is especially vulnerable to inland flooding since the rivers are relatively short and it is more likely that high river discharge resulting from rain will coincide with the storm surge (unlike for the case with large rivers where there is a long lag time between rain and river flooding).
The ADCIRC mesh has been highly refined in southern New England. In the Rhode Island region, the new mesh properly resolves the complicated coastal geometry of Narragansett Bay and the southern Rhode Island coast including narrow inlets, salt ponds and the presence of the Fox Point Hurricane Barrier in Providence. The ADCIRC mesh boundaries over land have been reconfigured to allow river inflows from the major rivers for combined inland and coastal flood modeling (Ullman et al. 2019).
Figure: High-resolution ADCIRC mesh in southern New England. The locations by magenta circles show where river transport is prescribed in order to simulate the effects of riverine flooding. The included rivers are the Mystic, Charles, and Neponset in the Boston area, the Taunton in Massachusetts, the Blackstone, Moshassuck, Woonasquatucket, and Pawtuxet in Rhode Island, and the Connecticut in eastern Connecticut.
Advancing hurricane wind modeling during landfall
Accurate modeling of surface winds during hurricane landfall is critical for predicting power outages and infrastructure damage over land and coastal flooding due to storm surges. As a hurricane moves from sea to land, the surface roughness it encounters abruptly increases causing significant changes to the structure of surface winds. Such changes include a rapid decrease in wind speed magnitude and a change in wind direction at the coastline. Parametric wind models commonly applied for wind damage assessment and storm surge models are typically too simplistic to sufficiently represent these complex wind structure changes. To overcome these limitations, we have developed a high- resolution hurricane boundary layer (HBL) model that incorporates the important physical processes in the three-dimensional dynamics equations (Gao and Ginis 2016, 2018).
Advancing the physics of atmosphere-wave-ocean coupling in storm surge models
This project will employ an innovative methodology for coupling storm surge and wave models (to obtain a more accurate flooding representation), based on previous URI research to develop coupled hurricane-wave-ocean models. This methodology accounts for wave-current interactions and a sea-state dependent drag coefficient. The new ocean circulation (storm surge)-wave model coupling method is accomplished by extending the Air-Sea Coupling Module (ASCM), originally developed at URI for deep-water conditions, to finite/shallow water conditions (Chen et al. 2020). The ASCM is being implemented into the ADCIRC and with the new, unstructured grid version of WW3 recently developed at NOAA NCEP/EMC.