報告書番号

V09038

タイトル（和文）

海洋レーダを用いた表層塩分の観測方法の提案

タイトル（英文）

Measuring sea surface salinity and sea surface temperature using ocean radar

概要 （図表や脚注は「報告書全文」に掲載しております）

海域における塩分や水温は海域の流況に大きく影響していると共に，生物の生息環境においても重要な役割を果たしており，それらを計測する事の重要性は高い．本報告書では，広域の観測の効率化のために，海洋レーダの受信電力を用いた沿岸域の表層塩分，表層水温の計測方法を開発し,その有効性を検討した．本手法は，海洋レーダの受信電力から海域の電気伝導度を算出し，それを用いて表層水温，表層塩分を算出する．諫早湾湾口部におけるVHF帯海洋レーダの観測結果を用いて本手法を検討した結果，表層塩分については計測結果と定性的に一致しており，夏期の有明海内の塩分成層の形成・発達過程を捉えることが可能であった．表層水温については，５日平均をとると水温の季節変動を定性的に捉えていたが，短期的な変動成分が大きく，計測精度に課題があることが分かった．

概要 （英文）

The sea surface salinity (SSS) and the sea surface temperature (SST) were measured using the VHF ocean radar. We have developed the estimation method for the sea surface electric conductivity (SSE) using the first order scattering intensity appeared in the Doppler spectrum. The SSE is calculated from the receiving signal intensity by estimating the first order scattering cross section and the propagation loss of the transmitting radio wave due to the ocean wave spectrum of the Bragg scattering wave and the SSE. If either SSS or SST is available in addition to the SSE, the other factor can be estimated using the relationship between SSS, SST and SSE. To examine the applicability of the developed method, the SSS and the SST were measured through the observation at the Ariake Sea using the VHF ocean radar. The estimated SSS shows reasonable agreement with the measured. The daily mean SSS indicates that the salinity stratification in the Ariake Sea developed after the swollenness of the Chikugo River, and the SSS gradually decreased with the following increases of the river runoff. These results are consistent with the observation results by Hamada et al. (2007). Additionally, the seasonal fluctuations in the estimated SST was in relatively good agreement with the measured one, except for the summer when the SSS decreased due to the presence of the salinity stratification. These results show that ocean radars have the potential use in measuring SSS over a large span of spatial and temporal scales.

報告者

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