Studies on the Fluctuations of Limnological Conditions in Lake Yogo (I)
Coefficients of Vertical Thermal Diffusivity
1978 Volume 39 Issue 1 Pages 29-36
Details
1978 Volume 39 Issue 1 Pages 29-36
Measurements of air and water temperature had been carried out at Lake Yogo from January, 1969 to January, 1970. Using these continuous records, characteristics of the seasonal variation in limnological conditions in Lake Yogo are described. Coefficients of vertical thermal diffusivity, Kz, are evaluated for 6 layers of water with time scales from a day to a month. Ignoring the absorption of solar radiation in evaluation of thermal diffusivity, coefficient Kz becomes about 10% larger. In the period when lake water is stratified, coefficient Kz in the upper layer is larger than in the lower one, namely about 0.2 cm2/sec in 3m layer and about 0.04 cm2/sec in 7m layer. It is shown that, the larger the vertical gradient of water temperature is, the smaller the coefficient Kz is, and that the value of Kz is about 0.08 cm2/sec at ∂T/∂z=1.0°C/m and about 0.5 cm2/sec at ∂T/∂z=0.1°C/m.
