A note on the adjustment towards geostrophic equilibrium in a simple fluid system

A simple fluid system is used to study numerically how the atmosphere reaches a geostrophic equilibrium from a non-geostrophic initial state. Most of the previous studies on atmospheric adjustment have emphasized the initial and final states. Furthermore, they have usually considered motions smaller or larger than the radius of deformation. This study explores the adjustment process for scales both greater and smaller than the radius of deformation. The role of gravity-inertial waves in the adjustment process is clearly shown by the numerical results and by an accompanying theoretical discussion.

Finally, some speculation of the implications of atmospheric adjustment towards the problem of providing initial data (termed initialization) for primitve equation numerical weather prediction models is discussed.