On the distribution of helicity in the tropical cyclone boundary layer from dropsonde composites

摘要: Abstract This study analyzes GPS dropsonde data in multiple tropical cyclones from 1997 to 2017 investigate the boundary layer structure with a focus on helicity distribution. A helicity-based method for height is developed and evaluated by comparing it other scales including inflow depth, of maximum tangential wind speed thermodynamic mixed depth. Our composites confirmed radial variations these heights seen previous studies. The results show that defined vertical gradient closest or jet located between depth all intensity groups. All three kinematic generally decrease storm at given radius. These converge major hurricane group, while much larger than two group. normalized 100–200 m altitude which close inflow. Both front-back downshear-upshear asymmetries are observed 0–1 km integrated inner core region storm, front downshear sides also magnitude stronger storms. Application quantify turbulent characteristics discussed.