- Surface waves play a vital role in air-sea interactions, and being able to easily measure them in-situ validates and improves predictive models. Here, we diagnose surface wave properties in the Bay of Bengal using modified vertical SOLO II profiling floats, which are regularly used as part of the Argo ocean float array. The modified χSOLO floats measure high frequency pressure, acceleration, velocity fluctuations, and turbulence data, in addition to traditional conductivity-temperature-depth data. The pressure and acceleration data are used to compute surface wave frequency and height for swells and surface wind waves. The frequency of the swells is computed using power spectral density of vertical acceleration at the bottom of a vertical dive, and surface wind wave frequency is computed using power spectral density of the pressure record while at the surface. To find amplitude, the observed frequencies are individually identified in depth-binned Fourier transforms of the net horizontal acceleration. The magnitudes of these Fourier components are fit to an exponential decay as a function of depth, and the terms of this fit give the amplitude of the wave component corresponding to that frequency. These methods unveil a series of swells of roughly half meter amplitude generated between 7000 km and 9500 km away and two short period wind wave bands of ~4 s and ~7 s with amplitudes 0.1 m and 0.3 m, respectively. The observed waves agree well with model predictions from the global WaveWatch III simulations.
Keywords: Ocean Waves, Spectral Analysis, Vertical Profiling, WaveWatch