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Directional Wave Spectra Observed During Intense Tropical Cyclones
Author(s) -
Collins C. O.,
Potter H.,
Lund B.,
Tamura H.,
Graber H. C.
Publication year - 2018
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2017jc012943
Subject(s) - typhoon , swell , tropical cyclone , storm , climatology , geology , wind speed , meteorology , maximum sustained wind , wind wave , atmospheric sciences , environmental science , wind shear , oceanography , geography , wind gradient
Abstract Two deep‐sea moorings were deployed 780 km off the coast of southern Taiwan for 4–5 months during the 2010 typhoon season. Directional wave spectra, wind speed and direction, and momentum fluxes were recorded on two Extreme Air‐Sea Interaction buoys during the close passage of Severe Tropical Storm Dianmu and three tropical cyclones (TCs): Typhoon Fanapi, Super Typhoon Megi, and Typhoon Chaba. Conditions sampled include significant wave heights up to 11 m and wind speeds up to 26 m s −1 . Details varied for large‐scale spectral structure in frequency and direction but were mostly bimodal. The modes were generally composed of a swell system emanating from the most intense storm region and local wind‐seas. The peak systems were consistently young, meaning actively forced by winds, when the storms were close. During the peaks of the most intense passages—Chaba at the northern mooring and Megi at the southern—the bimodal seas coalesced. During Chaba, the swell and wind‐sea coupling directed the high frequency waves and the wind stress away from the wind direction. A spectral wave model was able reproduce many of the macrofeatures of the directional spectra.