A Numerical Model Simulation of Atmospheric air Motion in Shallow Water Domain: Performances with Respect to Global Model
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Date
2009-06
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Addis Ababa University
Abstract
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
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Performances with Respect to Global Model