Using a Physical Reference Frame to Study Global Circulation Variability

The 3D structures of the free oscillations of an adiabatic and hydrostatic atmosphere around a basic state at rest were used as a physical filtering for atmospheric data. This filtering procedure allows for the consideration of the three primitive variables (u, , ) over the whole atmosphere simultaneously. Accordingly, the computed statistics do not simply rely on the information provided by a single variable of circulation, such as the 500-hPa geopotential field.