Process Study of Oceanic Responses to Typhoons Using Arrays of EM-APEX Floats and Moorings
Final rept. 1 Mar 2008-31 Mar 2015
WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB
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Between 2009 and 2010, as a part of The Impact of Typhoons on the Ocean in the Pacific ITOP program, we deployed four surface moorings and three subsurface moorings in western Pacific on the prevailing path of tropical cyclones, based on the analysis of paths of historical tropical cyclones. Each of surface moorings was equipped with meteorology sensors on the surface buoy and underwater CTD sensors. Each of subsurface moorings was equipped with one 75-kHz ADCP, capable of measuring current velocity in the upper 500 m. In Sept 2010, an array of seven EM-APEX floats was launched from C130 one day before the eye of Typhoon Fanapi hit the center of the float array. EM-APEX floats measured temperature, salinity, pressure, and horizontal velocity. In Oct 2010, another array of seven EM-APEX floats were launched from C130 one day before the eye of Typhoon Megi hit the southern end of the float array. The thermal evolution of the cold wake of Typhoon Fanapi, 2010, was studied Mrvaljevic et al., 2013. The cold wake formed by Typhoon Fanapi was 2.5 C cooler than the surrounding water, and extending to 80 m, twice as deep as the preexisting mixed layer. Four days after the formation, the cold wake was capped by a think warm surface layer. The thickness of the subsurface capped wake, decreased with time toward its background value with an e-folding time of 23 days, almost twice the e-folding lifetime of the SST cold wake 12 days. The wake was advected several hundreds of kilometers from the storm track by a preexisting mesoscale eddy. These observations reveal new intricacies of cold wake evolution and demonstrate the challenges of describing the thermal structure of the upper ocean using sea surface information alone. D Asaro et al. 2014 studied the cold wake response and air-sea fluxes. The strengths and properties of cold wakes depended most heavily on the nondimensional storm speed.
- Physical and Dynamic Oceanography