Inland Evolution of Near-Surface Winds During Tropical Cyclone Landall

How well do current turbulence parameterizations represent the near-surface, post-landfall tropical cyclone (TC) wind field? This question is critical for understanding and predicting the societal impacts of landfalling TCs. Owing to a lack of observations and challenges associated with conditions well outside the standard parameter space, there have been limited studies addressing this question. The goal of this research is to begin comparisons of standard turbulence parameterizations over land in the immediate vicinity of the coastline to large-eddy simulations. Our working hypothesis is that the traditional parameterizations underestimate the near-surface wind speed in the immediate vicinity of the coast. We use idealized simulations of a landfalling TC to test this hypothesis using the Weather Research and Forecasting (WRF) model version 4.5. Our experimental domain includes a fixed sea-surface temperature and a homogenous land mass; the idealized TC makes landfall at an angle nearly perpendicular to the coast. Our simulations use the Mellor-Yamada-Nakanishi-Niino (MYNN) PBL with non-local components of the EDMF scheme enabled, the Yonsei University (YSU) PBL scheme, and an experimental large-eddy simulation in the same environment. The MYNN and YSU schemes indicate a near-instantaneous weakening of the 10-m wind field at landfall. (Qualitatively, similar trends in the wind field are observed with landfalling TCs modeled by the HWRF, HAFS, and HMON hurricane dynamical models.) Here, we ask: Is this depiction of inland winds realistic? If so, what dynamic interactions occur at landfall that lead to this rapid contraction and dissipation of winds? Next, we test our initial hypothesis by comparing these results with output from an LES in a similar coastal environment.