Inertial instability

Inertial instability arises from mismatches between the pressure gradient force and centrifugal forces for a parcel displaced radially in an axisymmetric (i.e., independent of longitude) vortex (Andrews et al., 1987) and are found to be important for atmospheres where 0.25 < Ri < 1. They are driven primarily by the vertical eddy stresses associated with the vertical wind shear of thermal winds and transport heat both down the horizontal temperature gradient and vertically upwards, thereby increasing both the static stability of the atmosphere and Ri.

Inertial instability has been proposed as a mechanism to account for the formation of banded structures in giant planet atmospheres since it leads to axisym-metric motions consistent with the banded structure (Stone, 1976). Inertial instability may also explain the cloud structure on smaller scales such as in the Great Red Spot (GRS) since a second condition for inertial instability is that absolute vorticity is negative within a certain latitude band: that is,

It can be seen that the second condition for inertial instability favors regions of anticyclonic vorticity. Hence, in such anticyclonic eddies, inertial instability may create turbulence and thus enhanced cloudiness as is observed.

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