Basic study on baroclinic variations of the Kuroshio estimated from IES data

利用布设在芦折角近海和近海的IES（Inverted Echo Sounders）资料，采用GEM（Gravest Empirical Mode）方法估算了温度和盐度的垂直廓线，并计算了海面动力高度（SSDH）。由这些SSDH的差异，得到了黑潮在两站间的斜压输送时间序列。IES派生的SSDH与CTD派生的相比，均方根（均方根）差为3.2厘米的沿海网站和2.5厘米的离岸网站。同时，由CTD数据得到的SSDH异常与卫星测高数据得到的SSDH异常之间的比较结果在沿海和近海站点分别为3.6 cm和2.9 cm rms差异。这些结果证实，从CTD数据确定的SSDH是更接近的IES数据比测高数据。另外，由CTD垂直温度廓线估算出的空间高度分量在高度计中为5 cm，而在IES资料中仅为2 cm，我们还继续对黑潮的变化进行了描述，并准备了与IES资料进行比较的数据集。特别是，沿四国ASUKA观测线沿着的水文数据是由R/V Tanseimaru的KT 05 -23巡航获得的，并且时间序列的周期被扩展为黑潮轴位置的变化，所述黑潮轴位置的变化是根据通过组合测高数据和表面漂移数据获得的表面速度场来估计的。特别是后者揭示了IES资料所得到的黑潮斜压输送的变化受黑潮轴位置变化的强烈影响。

Vertical profiles of temperature and salinity are estimated by the GEM (gravest empirical mode) method from the IESs (inverted echo sounders) data deployed on coastal and offshore sites off cape Ashizuri, and then sea-surface dynamic height (SSDH) are calculated from those profiles. From difference of these SSDHs, a time series of baroclinic transport of the Kuroshio between these two stations are obtained. The IES-derived SSDH is compared with CTD-derived one ; the rms (root-mean-square) difference is 3.2 cm on the coastal site and 2.5 cm on the offshore site. Meanwhile, comparison between the SSDH anomaly derived from the CTD data and that obtained from the satellite altimetry data results in 3.6 cm and 2.9 cm rms differences on the coastal and offshore sites, respectively. These results confirm that the SSDH determined from the CTD data is closer to that of the IES data than that of the altimetry data. In addition, the steric height component confined in the surface-layer is estimated from the CTD vertical temperature profile as 5 cm in the altimetry but only 2 cm for the IES data.We also continued to add description on variations of the Kuroshio and to prepare dataset being compared with the IES data. In particular, hydrographic data along the ASUKA observational line off Shikoku are acquired by KT05-23 cruise on R/V Tanseimaru, and the period of the time series is expanded for variations of the Kuroshio axis position estimated from the surface velocity field obtained by combining the altimetry data and surface drifter data. Especially, the latter reveals that variations of the baroclinic transport of the Kuroshio obtained by the IES data are strongly influenced by variations of the Kuroshio axis position.We made a summary report on our achievements during this 3-year period.