Chapter 9 Flashcards
Inertial waves
are a type of mechanical wave possible in rotating fluids.
Inertial waves are a type of mechanical wave possible in rotating fluids. Unlike surface gravity waves commonly seen at the beach, inertial waves flow
through the interior of the fluid, not at the surface.
. Like any other kind of wave, an inertial wave is caused by
a restoring force and characterized by its wavelength and frequency.
. Like any other kind of wave, an inertial wave is caused by a restoring force and characterized by its wavelength and frequency. The restoring force for inertial waves is the
the Coriolis force. Inertial waves are transverse.
Inertial waves are restored to equilibrium by the Coriolis force. To be precise, the Coriolis force
arises (along with the centrifugal force) in a rotating frame.
Inertial waves, therefore, cannot exist without
rotation
Inertial waves are possible only when
a fluid is rotating, and exist in the bulk of the fluid, not at its surface.
inertial waves are transverse, which means that their vibrations occur perpendicular to the direction of wave travel.
One peculiar geometrical characteristic of inertial waves is that their phase velocity, which describes the movement of the crests and troughs of the wave, is
perpendicular to their group velocity, which is a measure of the propagation of energy.
Whereas a sound wave or an electromagnetic wave of any frequency is
possible
Whereas a sound wave or an electromagnetic wave of any frequency is possible, inertial waves can exist only over
the range of frequencies from zero to twice the rotation rate of the fluid.
Whereas a sound wave or an electromagnetic wave of any frequency is possible, inertial waves can exist only over the range of frequencies from zero to twice the rotation rate of the fluid. Moreover, the frequency of the wave is determined by
its direction of travel.
Waves traveling perpendicular to the axis of rotation have
zero frequency and are sometimes called the geostrophic modes.
Waves traveling perpendicular to the axis of rotation have zero frequency and are sometimes called the geostrophic modes. Waves traveling parallel to the axis have
maximum frequency (twice the rotation rate), and waves at intermediate angles have intermediate frequencies.
Inertial waves are observed most commonly
in planetary atmospheres (Rossby waves, geostrophic winds) and in oceans and lakes (geostrophic currents), where they are responsible for much of the mixing that takes place
Inertial-gravity waves occur when the flow is
statically stable
Inertial-gravity waves occur when the flow is statically stable. They are essentially
gravity waves that have a large enough wavelength to be affected by the earth’s rotation.
for inertial-gravity waves the group velocity and phase velocity are
orthogonal
Thus, for inertial-gravity waves the group velocity and phase velocity are orthogonal, and upward propagating waves transport energy
downward
The parcel trajectories for inertial-gravity waves are
ellipses
K•V = 0.
This means that the
velocity is always perpendicular to the wave number vector; i.e., there is no component of particle motion along the direction of the phase propagation. Therefore, the ellipses are always at 90° to the direction of phase propagation.
The particles move along these ellipses in an ……………….. fashion (in the Northern Hemisphere), regardless makes sense, since the Coriolis force must be directed toward the ………….
anticyclonic
the inside of the ellipse
