Influence of Meteorological Forcing Resolution on Simulations and Future Projections of Storm Surge in Hurricane Katrina

Storm surge is estimated to cause almost half of fatalities associated with tropical cyclones (TCs) in the United States, motivating the need for reliable future projections. TC wind and pressure fields are used as meteorological forcing inputs to model storm surge. These fields are often obtained from climate model simulations and are highly sensitive to model characteristics such as the horizontal resolution. However, it is unclear how different forcing resolutions will impact the simulation and future projections of storm surge. Here, we used regional climate model simulations of Hurricane Katrina at 27 km, 4.5 km, and 3 km resolutions to drive storm surge simulations of Katrina in historical and future climates using the ADvanced CIRCulation (ADCIRC) model. The meteorological forcings were based on hindcasts of Hurricane Katrina, which represent Katrina under the actual historical conditions in which it occurred, and future simulations using the pseudo-global warming modeling approach, which represent Katrina if it occurred in a warmer future scenario. We found that simulated storm surge is sensitive to the forcing resolution in both the historical and future climates, with the lowest peak surge heights in the 27 km forcing. The forcing resolution did not influence the sign of future surge projections, as peak surge heights increase across all resolutions. However, the magnitude and spatial extent of the future change is highly sensitive to forcing resolution. In addition, we investigated the duration of storm surge and found that it is sensitive to the forcing resolution in both climates. Storm surge duration decreased by ~5% in the future across all the resolutions, implying that the forcing resolution will not influence the sign of projected future changes to storm surge duration. The decrease in storm surge duration was linked to a reduction in the TC lifetime over ocean for all three resolutions.