Study on the variations of vertical flow, Ater temperature and dissoved oxygen during free convection overturn in lake

由于测量难度大，一直没有对自由对流翻转期的湖流垂直分量进行测量。超声波电流计的应用解决了这一问题，该装置在本研究中得到了广泛应用。观测主要集中在山石县的小山地湖泊石炭湖，与前期研究结果一致，水团垂直交换夜间增加，白天减少。除了垂直流的日变化外，还记录了一些临时波动。这些波动被认为是由平流和内波引起的。水温是理解垂直速度记录的一个有用的因素，但溶解氧在这一分析中只提供了很少的信息。在小湖泊中，即使在翻转期间，地表温度也有很大的变化。因此，垂直速度也表现出明显的日变化。通常，最大速度出现在清晨，约为+ - 2cm/秒。与水平流相比，这种速度非常慢，但在分析热交换和物质交换方面具有重要意义。

Measurement of the vertical component of lake flow during free-convection overturn period has not been made because of the difficulty in the measurement. This problem was resolved py the application of ultra-sonic current neter, and this device is widely used in this study.Observations were mainly made in Lake Shibire, a saall mountain lake in Yamansshi Prefecture, As expected from the preliminary study, the vertical exchange of water mass increases during night and reduced in daytime. Beseides the daily variation of the vertical flow, some temporary fluctuations were also recorded. These fluctuations are assumed to be induced by advection and internal wave.Water temperature is and useful element in understanding the record of the vertical velocity, but dissolved oxygen affords only a little imformation on this analysis. In small lakes, surface temperature varies considerably even during the over-turn period. Thus the vertical velocity also shows clear diurnal change. Usually, maximun velocity appears in the early morning, and it is about + - 2cm/sec. This velocity is extremaly slow as compared with the horizontal current, but has important significance in analyzing heat and material exchanges.