Ali’s Dispersion Control

Ali’s Dispersion Correction is a correction to the dispersive behavior of very long waves in a compressible ocean on an elastic Earth. It is intended to be used in lieu of the self-attraction and loading tide prescribed through the fort.24 file. It should be used with the sixth-digit of IM equal to 3 (fully implicit gravity wave term).

Version

This is considered a technical preview in version 55. Theoretical work is still ongoing.

Controlling Dispersive Behavior

The feature is triggered by the presence of the &AliDispersionControl namelist at the bottom of the fort.15 file. Here is an example of how this line is used (the following floats are the default values):

&AliDispersionControl CAliDisp=T, Cs=1500.0, Ad = 0.0050189, Bd = 0.23394/

• CAliDisp logical flag to turn Ali’s dispersion correction on (F=false by default).

• Cs is the speed of sound in water [m/s] for the Mach number based dispersive correction. Set Cs to a negative value to turn the Mach number based correction off.

• Ad the power law constant.

• Bd the power law exponent.

For the following equation: \(Correction = 1 - \frac{Ma^2}{4} - {A_d}H^{B_d}\)

where Ma is the Mach number (\(Ma = \frac{\sqrt{gH}}{Cs}\)) and H is the total water depth.