Boundary Layer Observations and Near-Surface Wind Estimation During the Landfalls of Hurricanes Ida (2021) and Zeta (2020)

Abstract

This study examines the boundary layer wind profile and turbulence variables during the landfalls of Hurricanes Ida (2021) and Zeta (2020) using ground-based Doppler radar observations and a nearby anemometer's wind measurements. While the radar sampled different parts of the hurricane circulation of the two cases, the observed maximum near-surface wind and frictional velocity were similar. Radar-retrieved wind profiles in both hurricanes revealed a boundary-layer jet generally >1 km AGL, descending toward smaller radii as the hurricanes moved inland. A “knee-like” structure in most wind profiles below the jet suggests an internal boundary layer (IBL) below 200 m and a log layer above it. Among the three methods for estimating near-surface sustained winds from radar-retrieved winds, leveraging low-level IBL winds improves estimation accuracy and reduces the uncertainty to the selection of upstream surface roughness length. These findings offer valuable guidance for developing future probabilistic near-surface wind products.