The Effect of Roll Vortices on Turbulent Fluxes in the Hurricane Boundary Layer

The patterns observed in surface wind fields derived from synthetic aperture radar (SAR) images inside and around tropical cyclones (TCs) were investigated with data from RADARSAT-1 Satellite. Supporting field measurements obtained on research flights of the NOAA/Aircraft Operations Center (AOC) WP-3D aircraft provide a database for the interpretation of the unique features of the hurricane structure. The aircraft data include flight level winds and turbulence measurements of momentum and water vapor fluxes, dropsonde information, temperature, and surface winds obtained remotely by a stepped-frequency microwave radiometer (SFMR). The hypothesis that linear streaks observed in the SAR wind fields between rainbands were due to secondary flows, roll vortices, in the atmospheric boundary layer is verified. Our data analyses show that their contribution to the net fluxes and their distribution azimuthally around the storm could play an important role in boundary layer air-sea fluxes and hurricane dynamics. Many cases of roll-vortex signatures in the SAR wind fields in hurricanes are also documented. This work may play a role in developing parameterization of these features for future use in operational coupled numerical hurricane forecast models.