Effects of Surface Water over Land on Landfalling Hurricanes: A Numerical Investigation with the GFDL Hurricane Model

The role of land surface water in retarding landfall decay and maintaining landfalling hurricanes was little investigated and suspected to be not significant because of the evaporation-induced land surface cooling which leads to hurricane decoupling with its underlying land surface. This study, using the Geophysical Fluid Dynamics Laboratory/NOAA hurricane model, investigated the landfalling hurricane-land surface water interactions focusing on the local land surface temperature cooling, surface flux reduction, and their impacts on hurricane structure and intensity. Different water depth and surface roughness conditions were incorporated in the experiments starting with a Fran96-like bogus embedded in an uniform easterly mean flow of 5m/s. Results showed that surface evaporation is the primary cause of the major local surface cooling during night while the cloud effects on solar radiation enhance the local surface cooling around the core during the day. A layer of half meter water noticeably retards landfall decay and retains a hurricane of a certain intensity. This makes the case significantly different from both the ocean case with a large intensity reduction and the dry land surface case in which landfalling hurricane finally diminishes off.