Scaling of Drag Coefficients Under Five Tropical Cyclones
Abstract
The drag coefficient, often used to parameterize the surface wind stress τ, beneath tropical cyclones (TCs) is a critical but poorly known factor controlling TC intensity. Here, τ is estimated using current measurements taken by 12 Electromagnetic Autonomous Profiling Explorer floats beneath the forward half of five TCs. Combining estimates of τ and aircraft measurements of winds U10, the downwind drag coefficient and the angle ϕ clockwise orientation from U10 to τ are computed. At |U10| = 25–40 m/s, and ϕ vary over (0.8–3.1) × 10−3 and −15–40°, respectively. A new nondimensional parameter “effective wind duration,” a function of |U10|, storm translation speed, and positions in TCs, predicts to within 25%. The largest and smallest ϕ occur at high winds, in the forward right quadrant of fast‐moving storms. These dependences are explained by variations in surface wave age and breaking under different wave forcing regimes.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Mar 21, 2019
- Source ID
- 10.1029/2018gl081574
Entities
People
- Eric A. D'Asaro
- Je‐Yuan Hsu
- Ren‐Chieh Lien
- Thomas B. Sanford
Organizations
- Commonwealth Scientific and Industrial Research Organisation
- Office of Naval Research
- University of Washington