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http://dx.doi.org/10.5467/JKESS.2013.34.1.51

Sensitivity of Numerical Solutions to Time Step in a Nonlinear Atmospheric Model  

Lee, Hyunho (School of Earth and Environmental Sciences, Seoul National University)
Baik, Jong-Jin (School of Earth and Environmental Sciences, Seoul National University)
Han, Ji-Young (Korea Institute of Atmospheric Prediction Systems)
Publication Information
Journal of the Korean earth science society / v.34, no.1, 2013 , pp. 51-58 More about this Journal
Abstract
An appropriate determination of time step is one of the important problems in atmospheric modeling. In this study, we investigate the sensitivity of numerical solutions to time step in a nonlinear atmospheric model. For this purpose, a simple nondimensional dynamical model is employed, and numerical experiments are performed with various time steps and nonlinearity factors. Results show that numerical solutions are not sensitive to time step when the nonlinearity factor is not influentially large and truncation error is negligible. On the other hand, when the nonlinearity factor is large (i.e., in a highly nonlinear regime), numerical solutions are found to be sensitive to time step. In this situation, smaller time step increases the intensity of the spatial filter, which makes small-scale phenomena weaken. This conflicts with the fact that smaller time step generally results in more accurate numerical solutions owing to reduced truncation error. This conflict is inevitable because the spatial filter is necessary to stabilize the numerical solutions of the nonlinear model.
Keywords
time step; nonlinear atmospheric models; numerical solutions; small-scale phenomena; spatial filter;
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