The broad term for positioning satellites, including GPS launched by the United States, is Global Navigation Satellite Systems (GNSS). Of GNSS, remote sensing utilizing the phenomenon whereby signals from positioning satellites are reflected on the sea surface and the land is called GNSS-R (Reflectometry). GNSS-R utilizes existing positioning signals, making simultaneous observation from several sites possible. Therefore, GNSS-R now has excellent potential as a low-cost monitoring method for natural phenomena that change quickly, including typhoons and bomb cyclones.

In estimating physical parameters, including sea surface winds, ocean waves, tsunamis, and storm surges, using GNSS-R, we should focus on the following important points: we will elucidate the physical phenomena of "wavelets" in actual sea areas, and will then quantitatively evaluate the relationships of such physical phenomena with dispersion signals from the sea surface.

In this study, we conducted comprehensive in-situ observations of ocean waves and associated physical parameters, sea surface winds and wave-induced mixing, at Hiratsuka observation tower, University of Tokyo Ocean Alliance between March 28 and April 5, 2018. Moreover, we used a GNSS antenna to measure the magnitude of GNSS signals reflected from the sea surface.

Going forward, we will analyze the obtained data. In particular, regarding direct measurement of higher wave number spectra with wavelengths of up to approximately 10 cm and source balance at their frequency zones, there are many unknowns. In estimating wavenumber spectra, the wavelet directional method proposed by Donelan et al. (1996) is used. In addition, we aim to clarify independently the following: the physical processes of the ocean wave boundary layer using measured ocean wind turbulence; turbulence mixing associated with breakers using marine surface layer turbulence, and the effects on higher wave number spectra, which are associated with turbulence mixing.