Upper Ocean Response to Super Typhoon Mangkhut from a Profiling Float Array

An array of 8 SOLO-II profiling floats was deployed from R/V Thompson along 134.5^oW between 11^oN and 14^oN as part of a NOAA program in cooperation with ONR's PISTON initiative. The floats measured temperature and salinity in the upper 150 m every 38 minutes before, during, and after Super Typhoon Mangkhut. From 29 August to 2 November 2018, almost 20,000 profiles were completed. One float continues to operate past 2 November.

Two floats were within 10-30 km of Mangkhut's eye on 13 September 2018 (Japan Meteorological Agency- JMA). The remaining 6 floats were situated well within the radius of gale winds (JMA). The two floats nearest Mangkhut's eye measured mixed layer (ML) heat loss of 200 MJ m^-2, a ML cooling of 1^oC, a ML deepening of up to 100 m (or about 30 m with a 2-day lowpass). The transient near-inertial (NI) response obtained by bandpassing depth-varying potential density and depth-mean velocity of each float indicates maximum potential energy density of 1 J m^-3 and kinetic energy density of 5 J m^-3 near the typhoon's eye. NI motions decay after about 11 days.

From the array as a whole, several features are noted: (a) NI motions are strongest to the right of the typhoon track, (b) ML cooling is strongest to the right, (c) ML salinity increased by mixing from below as floats crossed the typhoon track, and (d) ML cooling persisted for about 30 days within about 100 km of the passage of Mangkhut's eye. Further ML cooling at the float array occurred during the busy 2018 typhoon season with the passage of Super Typhoons Jebi, Kong-Rey, Trami, and Yutu.