Search Results
Abstract
A finite difference procedure is utilized for the solution of a coupled system of two ordinary differential equations governing the time averaged quasi-geostrophic perturbations in the atmosphere. The seasonal changes in the latitudinal mean state are found to introduce important phase changes and reversals in the asymmetric meridional circulation. A hypothetical latitudinal mean stability profile, which resembles many of the latitudinal mean stability profiles generally used in analytical studies, is found to give acceptable results in many cases. Barographic models for the zonal mean state are found to be incapable of giving acceptable quantitative results
Abstract
A finite difference procedure is utilized for the solution of a coupled system of two ordinary differential equations governing the time averaged quasi-geostrophic perturbations in the atmosphere. The seasonal changes in the latitudinal mean state are found to introduce important phase changes and reversals in the asymmetric meridional circulation. A hypothetical latitudinal mean stability profile, which resembles many of the latitudinal mean stability profiles generally used in analytical studies, is found to give acceptable results in many cases. Barographic models for the zonal mean state are found to be incapable of giving acceptable quantitative results
Abstract
Within the framework of a quasi-geostrophic model, the influence of different kinds of vertical profiles of diabatic heating on a stationary harmonic of the atmosphere is studied. Except in the cases in which there is a diabatic heating reversal in the upper layers of the atmosphere, the results show qualitative similarity, especially in phase. This lends support to the somewhat arbitrarily selected vertical profiles of diabatic heating used in many previous studies.
Abstract
Within the framework of a quasi-geostrophic model, the influence of different kinds of vertical profiles of diabatic heating on a stationary harmonic of the atmosphere is studied. Except in the cases in which there is a diabatic heating reversal in the upper layers of the atmosphere, the results show qualitative similarity, especially in phase. This lends support to the somewhat arbitrarily selected vertical profiles of diabatic heating used in many previous studies.
Abstract
Kurihara and Holloway have proposed an integration scheme that offers advantages in the problems of geophysical fluid dynamics by rigorously conserving mass and energy. We have attempted to investigate the accuracy of the Kurihara and Holloway method by numerical experiments, applying it to a problem for which an approximate analytic solution is available.
For the case in which the planetary wave number is 4, we find that with the equal-area grid and with a latitude grid spacing of 4.5°, the planetary wave is destroyed by truncation errors within 5 days. In order to achieve a solution with acceptable accuracy, in which the planetary wave character is retained for a minimum of 10 days, the grid spacing near the Pole has to be decreased by a factor of 9.
Abstract
Kurihara and Holloway have proposed an integration scheme that offers advantages in the problems of geophysical fluid dynamics by rigorously conserving mass and energy. We have attempted to investigate the accuracy of the Kurihara and Holloway method by numerical experiments, applying it to a problem for which an approximate analytic solution is available.
For the case in which the planetary wave number is 4, we find that with the equal-area grid and with a latitude grid spacing of 4.5°, the planetary wave is destroyed by truncation errors within 5 days. In order to achieve a solution with acceptable accuracy, in which the planetary wave character is retained for a minimum of 10 days, the grid spacing near the Pole has to be decreased by a factor of 9.
Abstract
Two smoothing techniques are tested as a practical means of allowing a larger time step in the numerical integration of a primitive equation free-surface model. The numerical integration uses a finite-difference grid and operators based on the method of Kurihara and Holloway.
A time step six times larger can be used with a corresponding six-fold decrease in computer time, by implementing the weighted averaging procedure given by Langlois and Kwok in their description of the Mintz-Arakawa general circulation model. A Fourier filtering scheme permits the use of a time step 10 times larger, and results in a five-fold improvement in computer time. After 10 days, the geopotential and wind fields obtained with these techniques still closely resemble the unsmoothed fields, the closest correspondence being found with the Fourier filtering technique.
In another set of experiments, steady-state solutions to special cases of the governing analytic equations are used as initial conditions in a test of the accuracy of the grid and operators. These steady-state solutions are preserved satisfactorily for the 10-day integration period.
Abstract
Two smoothing techniques are tested as a practical means of allowing a larger time step in the numerical integration of a primitive equation free-surface model. The numerical integration uses a finite-difference grid and operators based on the method of Kurihara and Holloway.
A time step six times larger can be used with a corresponding six-fold decrease in computer time, by implementing the weighted averaging procedure given by Langlois and Kwok in their description of the Mintz-Arakawa general circulation model. A Fourier filtering scheme permits the use of a time step 10 times larger, and results in a five-fold improvement in computer time. After 10 days, the geopotential and wind fields obtained with these techniques still closely resemble the unsmoothed fields, the closest correspondence being found with the Fourier filtering technique.
In another set of experiments, steady-state solutions to special cases of the governing analytic equations are used as initial conditions in a test of the accuracy of the grid and operators. These steady-state solutions are preserved satisfactorily for the 10-day integration period.
