Yasuhiro Murata, Toshiro Nagakura, Takahiro Kokai


HF Oceanographic radar is an equipment, for instantaneously sensing velocity distribution of sea surface current. It has a
wide field of view, which extends approximately ±45° in direction and beyond 50km in distance. There are high
expectations that the radar observation of Tsunami will become a new road path for preventing disasters. In this paper, we
describe a method to enhance the resolutions of radar in both time and current. At first, resolutions required for tsunami
observation are estimated by simulating a Tokachi-oki earthquake tsunami (2003). Here it is pointed out that traditional
data processing indicates inadequate resolutions for tsunami early detection. Secondly, two techniques are proposed to
achieve the necessary resolutions. Short-time Fourier transform (STFT), in place of normal FFT, enhances the time
resolution of Doppler analysis. Further, zero-padding technique improves the current resolution, by interpolation of data
within the frequency domain. Finally, by means of simulation, it is verified that these proposed techniques give improved
resolutions in both time and current.


Tsunami;Surface flow;HF Radar;Sea echo;Doppler shift;FFT;STFT;Zero-padding;Peak detection

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DOI: http://dx.doi.org/10.9753/icce.v32.currents.4