Early Student Support for a Process Study of Oceanic Responses to Typhoons
Abstract
Drag coefficients beneath Typhoon Megi in the western Pacific are computed using velocity measurements made by EMAPEX floats, and measurements of the 10m wind. Downwind drag coefficients increase to 3.70.2 x 103 at 31 m/s, a value greater than most previous estimates, but decrease to 1.80.1 x 103 for wind speeds > 45 m/s, in agreement with previous estimates. At wind speeds 3045 m/s significant crosswind wind stress is found such that the wind stress vector is about 20 degree clockwise from the 10m wind vector. This method is applied to five sets of EMAPEX float measurements taken under 5 different tropical cyclones. In all cases, the surface wind stress vector rotates clockwise from the 10m wind vector. The largest downwind drag coefficient occurs in the front right sector of the moving storms. The variation of drag coefficient is explained by the variation of wave breaking under different wave forcing regimes. Surface wave peak frequency and significant wave height under Typhoon Fanapi are computed using float measurements assuming JONSWAP spectrum. Float estimates of peak frequency are 1020 less than WAVEWATCH III (ww3) model results, and differences of significant wave height between float estimates and ww3 results are mostly < 2 m.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 21, 2018
- Accession Number
- AD1055222
Entities
People
- Ren-Chieh Lien
Organizations
- University of Washington