STUDY OF IMPACT FACTORS ON DATA ACQUISITION RATIO FOR DBF OCEAN RADAR WITH VHF BAND

The acquisition ratio of observational data by ocean radar presents a cyclic variation synchronized with tidal motion and an abrupt decreasing due to the meteorological conditions. Information relevant to the property of variation of the data acquisition and the impact factors on its variation is important for practical uses of ocean radar observation systems. The authors investigated the impact factors to the data acquisition ratio of the DBF(Digital Beam Forming) ocean radar with VHF band, central frequency 41.9MHz through long-term observation in Ariake Bay. As a result, the appearance of tidal flat along the coast off Arao mainly affected the cyclic variation of the data acquisition due to the transmission loss of radio waves. Besides, the flood from Chikugo River accompanied by heavy rainfalls and the decrease of conductivity at sea surface caused the abrupt decline of the acquisition ratio. At the term of weak wind less than 1m/s, the data acquisition also decreased by way of suppression of surface resonant wave.