| Abstract [eng] |
The main goal of the thesis is to create a visualisation system for the simulation results of numerical coupled model Shyfem/AQUABC and apply it for the investigation of ice cover effect to the natural aeration in the Curonian Lagoon ecosystem. The tasks of the work are to formulate the requirements for the visualisation system of modelling results; design and programmatically implement the visualisation system; formulate different scenarios for the investigation of ice cover effect; perform simulations of the model; apply the visualisation system for the analysis of model simulation results; and provide recommendations for further development of the system. The developed visualisation system consists of 8 different modules responsible for reading input files and parallelisation of the computations, processing biogeochemical and hydrodynamic variable data, and data conversion if needed. The system requires input files, in which the visualisation parameters, and station and variable visualisation information are specified. The parallelisation of the computations increases the speed of the processes. Analysis showed that the speed increases with the increased number of processors and reaches the maximum speed, when each variable is computed (plotted) on a separate core. Due to this the system allows user to quickly and easily obtain time series and depth profile (3D case) graphs of biogeochemical and hydrodynamic variables, time series graphs of biogeochemical state and derived variables data comparison of several model simulations, and files with statistical estimates. Several recommendations were presented for the further development of the system. Visualisation system was applied to studying ice cover effect on natural aeration in the Curonian lagoon. Five simulations have been carried out for studying the variations of dissolved oxygen. The analysis showed that during the ice cover period the greatest impact on dissolved oxygen concentration has the suppressed reaeration. Additionally there are noticeable concentration shifts in the summer time (ice cover effect on dissolved oxygen drags into the summer), this is due to the shift of phytoplankton growth, which also adds oxygen to the water in a process of photosynthesis. The analysis of oxygen saturation showed a noticeable decrease during the ice cover period, however the level of hypoxia (<30%) was not reached, and the decrease of values in the end of ice period, this might occur due to the long model spin up time, which might be resolved by adjusting initial conditions. The model takes into account just the percentage of ice cover (not the thickness of it or the snow cover on top of it), the solar radiation is not reduced when ice is present and ice cover data was interpolated over the entire lagoon from the data of just four monitoring stations. Overall, an improved model (and the use of satellite data) would improve the knowledge of ice cover effect on natural aeration in the water body. |
