Precise measurement of sea surface dynamic height by GPS kinematic survey and its application to Kuroshio studies

本研究开展了以下三项工作：（1）通过安装在渡轮上的GPS动态测量精确测量海面高度;（2）利用ADCP数据和TOPEX/POSEIDON高度计数据澄清研究区域的中尺度涡旋;（3）利用存档的温度数据研究研究区域的水团结构及其变化。主要结果可概括如下。(1)1999年9月，我们利用往返于东京和小笠原群岛之间的小笠原丸号渡轮进行了GPS动态测量。当两个GPS站（参考站和渡轮）的距离较短（小于数百公里）时，可以获得适合分析的数据。但是，发现距离相对较长，数据不适合分析。根据渡轮停泊在胡塔米港时获得的数据，我们可以足够准确地检测到潮汐信号。(2)利用ADCP资料和TOPEX/POSEIDON高度计资料，分析了黑潮回流区的中尺度涡旋。发现了大量直径约500公里的反气旋性和气旋性涡旋。时间尺度估计约为80天。认为这些涡旋是在黑潮延伸区形成的。(3)利用气温资料制作了格点气温资料，分析了副热带模态水量的年际变化与冬季东亚季风强度的关系。结果表明，冬季东亚季风强（弱）时，形成了厚（薄）冷（暖）副热带模态水。

In the present study, the following three items were carried out : (1) Precise measurement of sea surface height by GPS kinematic survey installed on a ferry boat, (2) clarification of mesoscale eddies in the studied area using ADCP data and TOPEX/POSEIDON altimeter data and (3) water mass structure and its variation in the studied area using the archived temperature data. Main results can be summarized as follows.(1) Using the ferry Ogasawara Maru which shuttles between Tokyo and Ogasawara Islands, we carried out the GPS kinematic survey in September 1999. We could obtain the data suitable for analysis when the distance of two GPS stations (the reference station and the ferry) is short (shorter than hundreds km). However, it was found that the distance is relatively longer, the data are not suitable for analysis. From the data obtained when the ferry was anchored at Hutami Port, we could detect the tidal signal with enough accuracy.(2) Using the ADCP data and TOPEX/POSEIDON altimeter data, we analyzed the mesoscale eddies in the Kuroshio recirculation area. We found a plenty of anticyclonic and cyclonic eddies whose diameter is approximately 500km. The temporal scale is estimated to be approximately 80 days. It was suggested these eddies are formed on the Kuroshio Extension area.(3) Using the archived temperature data, we made the gridded temperature data and analyzed interannual variation of subtropical mode water with respect to the strength of wintertime East Asia monsoon. It was found that when the wintertime East Asian monsoon is strong (weak), thick (thin) and cold (warm) subtropical mode water is formed.