Department of Science and Research, Islamic Azad University, P.O. Box 14155-775
Department of Surveying, University of Tehran, P.O. Box 11365- 4563
This research is based on a numerical model for forecasting the three-dimensional behaviour of (sea) water motion due to the effect of a variable wind velocity. The results obtained are then analyzed and compared with observations.
This model is based on the equations of motion temperature which are solved by finite difference assuming Δx, Δy as constants and Δz variable. The horizontal and vertical eddy viscosity and thermal diffusivity coefficients we used were in accordance with that of the Benet on Outario Lake (1977). Considering the Caspian Sea dimension in numerical model the Coriolis parameter used with β effects and the Boussinesq approximation have been used.
For modeling the Caspian Sea the grid of the field was done as follows. At horizontal surface, grid size was extended to 10×10km and at perpendicular in 10 layers with varying thickness from surface to bed respectively as: 5, 10, 20, 30, 50, 100, 150, 200, 250, 500 and higher. The data of wind as velocity, direction and temperature of water related to 15th September 1995 at 6, 12 and 18 o’clock were obtained from synoptic station at the Caspian Sea side and the research marine of Haji Alief. The information concerning seaside wind was measured by the SPM method and was transferred to far seaside winds through interpolation and by using inverse square distance, position distribution of the wind velocity at the Caspian surface field was obtained.
The model has been evaluated according to the reports and observations. Through studying the position of the current in different layers, the velocity in the cross section in the northern, southern and the middial layers, will be discussed. The current velocity throughout the whole field is different. The current velacity calculated ranges from 1.6cm/s to 15cm/s. The maximum velocity is observed in the middle, considering the maximum wind velocity 7m/s and wind stress .
The results reveal the presence of circulation cells in the three areas in an anti clockwise sense. The circulation with depth is reduced. The results obtained through the numerical solution of the temperature equation have been compared with the observations. The predicted temperature change in different layers with depth shows good agreement with observations.