Abstract: Some aspects of geostrophic adjustment are investigated by numerical experiment with nonlinear barotropic primitive equations in hemispheric area. The results are in good agreement with those obtained previously by both the linear and nonlinear theory. The characteristic time required for the adjustment process as well as the other quantitative data are given. The problem of four-dimensional assimilation is also discussed, indicating that it would not he of benefit, if the updating is made only in the pressure field without treatment of wind field.