MODELING THE DIURNAL MIXED LAYER IN A SHALLOW LAKE

The numerical model simulating several processes in the diurnal mixed layer is constructed based on the DIM (Dynamic Instability Model) type entrainment law derived by authors. The model has three noteworthy features. The first is that the entrainment speed is estimated according to the density gradient below the thermocline. The second is that the model describes not only the mixing process but also the heating process. The third is that the model is basically one-dimensional model but it can estimate the pressure force caused by surface tilt. The third feature is realized by solving the basic simultaneous equations consisting of the momentum, continuity equations and the entrainment law. The model is tested to input meteorological conditions just after rainy season in 1988 at the Lake Kasumigaura, and the results agree well with measured temperature and velocities.