A Numerical Model Simulation of Atmospheric air Motion in Shallow Water Domain: Performances with Respect to Global Model

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Addis Ababa University


An atmosphere is a gaseous envelope around a planet where a wide variety of physical, chemical and dynamical processes takes place. As a result atmospheric researchers can not do controlled experiment in the large scale atmosphere rather they look at an alternative method so called atmospheric modelling to understand the atmosphere. Among different kinds of modelling, in this thesis we apply Numerical modelling, where the processes taking place in the earth’s atmosphere are expressed in terms of mathematical equation (conservative principles), and experiments are done up on solving those mathematical equation. The validity of the model out put is checked by comparing it with the observed value or large global model which includes complete physics of the problem, by National Center for Environmental Prediction (NCEP) for this study. In this study, shallow water equation is used to simulate atmospheric air motion over mid latitude and Ethiopia on May 26, 2009. The result of the model out put for zonal velocity shows good agreement over mid latitude and Ethiopia. The discrepancy between our model and NCEP is ±2.22273 m/s over mid latitude and ±2.75427 m/s over Ethiopia on average. The result of model out put for absolute vorticity also agrees with NCEP data over mid latitude and Ethiopia. The discrepancy between our model and NCEP is ±0.00001 1/s over mid latitude and ±0.00004 1/s over Ethiopia. How ever, the discrepancy grows with prediction time. In general, this study shows that shallow water equation is good enough to capture many behaviors observed in earth’s atmosphere, and hence it can be used over any other region of the earths atmosphere to describe the horizontal atmospheric structure



Performances with Respect to Global Model