DEVELOPMENT OF LONG-TERM OBSERVATION SYSTEM OF THE HOLOCLINE IN COASTAL LAGOON

新研制了滨海泻湖盐跃层长期观测系统调查系统，并成功地对中湖和新地湖水声记录的分辨率进行了检验。这种测量系统可以自动提供回声探测剖面的时间序列，与传统的在自夸上装备的测量系统不同。传感器固定在湖底。新系统获得的回声探测记录足够清晰，可以区分出5个二叠世的盐斜。利用该系统对中海湖中心和边缘的盐跃层进行了观测。通过其他设备检测盐度、pH值、溶解氧、水温、流速和水流方向。这表明盐跃层容易移动，其行为受风的影响。用于测量远距离温度分布的光纤传感器可以同时产生多达4000点的温度数据，沿其间隔为1米。与上述回声探测系统一起在中见湖进行的实验有两个有趣的发现。一是湖底暖泉活动的时间变化。另一种是在气象强迫作用下，高咸水团向低咸水湖底运动。光纤分布式温度传感器的优点是可以方便地获得远距离温度数据的时间和空间函数。

The survey system of long-term observation system of the halocline in coastal lagoon was newly developed and the resolution of underwater acoustic records in Lakes Nakaumi and Shinjiwere successfully checked. This survey system, which automatically provides a time-series of echo-sounding profiles, is dirrerent from the conventional type equipped on a boast. The tranducer is fixed on the lake bottom. The echo-sounding recordobtained by the new ststem is clear enough to distinguish the 5 permill halocline.By using this system, we observed the halocline behavior at central and marginal place in Lake Nakaumi. Salinity, pH,dessolved oxygen, watertemperature, and water flow rate and direction were checked by the other equipments. This results suggested that the halocline was easily moved and that the behavior was influenced by wind.The optical fiber sensor for measuring temperature distribution over long distance can produce simultaneous temperature data at up to 4000 points with an interval of 1 m along it. The experiments used jointly with the above echosounding system in Lake Nakaumi have resulted in two interesting discoveries. The one is the temporal change of warm spring activity on the lake bottom. The other is the movement of a mass of high saline water into low saline water lake bottom driven by meteolological forcing. The advantage of the optical fiber distributed temperature sensor is its ability to easily obtain the temperature data as function of time and space over a long distance.