Vertical Profiles of Mean and Perturbation Structure of the Hurricane Boundary Layer from the GPS dropsondes

Vertical profiles of wind speed, potential temperature and specific humidity from the GPS dropsonde data collected during the Coupled Boundary Layer Air-Sea Transfer experiment are presented. The mean and perturbation profiles of the wind speed are normalized by the mixed layer depth that is defined from the potential temperature profile. Data from 950 sondes are grouped into five categories according to the mean wind speed of the lowest 150 m data. Our results show that the mean wind profiles follow the logarithmic function with altitude from around 40 to 200 m, although the wind profile from an individual sonde deviates from logarithmic. The perturbation profile is derived by subtracting a filtered mean profile from the original data for each sonde. The averaged perturbation profiles for the five categories confirm the presence of mesoscale features, such as rolls. The dropsondes are also separated by storm quadrant, showing the asymmetry of the mean profiles. The mechanisms causing the asymmetric distribution of the boundary layer mean structure by storm quadrant are also discussed.