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/ = / (+), which indicates that these long equatorial Rossby waves move in the opposite direction (westward) of Kelvin waves (which move eastward) with speeds reduced by factors of 3, 5, 7, etc. To illustrate, suppose c = 2.8 m/s for the first baroclinic mode in the Pacific; then the Rossby wave speed would correspond to ~0.9 m/s, requiring a 6 ...
Equatorial waves are oceanic and atmospheric waves trapped close to the equator, meaning that they decay rapidly away from the equator, but can propagate in the longitudinal and vertical directions. [1] Wave trapping is the result of the Earth's rotation and its spherical shape which combine to cause the magnitude of the Coriolis force to ...
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The eastward speed of propagation of these waves can be derived for an inviscid slowly moving layer of fluid of uniform depth H. [2] Because the Coriolis parameter (f = 2Ω sin(θ) where Ω is the angular velocity of the earth, 7.2921 × 10 −5 rad/s, and θ is latitude) vanishes at 0 degrees latitude (equator), the “equatorial beta plane” approximation must be made.
A geostrophic current may also be thought of as a rotating shallow water wave with a frequency of zero. The principle of geostrophy or geostrophic balance is useful to oceanographers because it allows them to infer ocean currents from measurements of the sea surface height (by combined satellite altimetry and gravimetry ) or from vertical ...
One can identify a terrestrial Rossby wave as its phase velocity, marked by its wave crest, always has a westward component. [1] [4] However, the collected set of Rossby waves may appear to move in either direction with what is known as its group velocity. In general, shorter waves have an eastward group velocity and long waves a westward group ...
The Rossby number is a dimensionless number which characterises the strength of inertia compared to the strength of the Coriolis force. The quasi-geostrophic equations are approximations to the shallow water equations in the limit of small Rossby number, so that inertial forces are an order of magnitude smaller than the Coriolis and pressure ...
For a barotropic ocean, the Rossby radius is () /, where is the gravitational acceleration, is the water depth, and is the Coriolis parameter. [ 2 ] For f = 1×10 −4 s −1 appropriate to 45° latitude, g = 9.81 m/s 2 and D = 4 km, L R ≈ 2000 km; using the same latitude and gravity but changing D to 40 m; L R ≈ 200 km.