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

新开发了沿海泻湖盐跃层长期观测系统的测量系统，并成功地检验了中海湖和新智湖水声记录的分辨率。该测量系统不同于传统的机载测量系统，能自动提供时间序列的测深剖面。传感器固定在湖底。利用该系统对中海湖中心和边缘的盐跃层进行了观测。通过其他设备检查盐度、pH、溶解氧、水温、水流速和方向。这一结果表明盐跃层很容易移动，其行为受风的影响。用于长距离测量温度分布的光纤传感器可以在沿盐跃层沿着1 m的距离上同时产生多达4000个点的温度数据。一是湖底温泉活动的时间变化。另一种是在气象强迫的驱动下，大量高盐水向低盐水湖底迁移。光纤分布式温度传感器的优点是它能够很容易地获得作为时间和空间的函数的长距离温度数据。

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.