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AliDispersionControl: Difference between revisions

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'''Dynamic Water Level Correction''' is a process by which modeled water levels are dynamically adjusted by use of a forcing term.  The correction can be applied as constant or varying in space and/or time.  The correction is applied as a forcing term in the momentum equations whose mathematical form is equivalent to that of an atmospheric pressure term.  This means that, for gradually-varying corrections, corrected water levels should closely follow the input correction, though these may deviate if a correction is applied very quickly or to an area that has a very weak connection to an open boundary through which water can flow. Further discussion is below in the [[#FAQ|FAQ]].
'''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).
 
Overviews and examples of this capability have been provided in multiple presentations (Luettich et al. 2017<ref name="luettichPres2017">Luettich, R.L., T.G. Asher, B.O. Blanton, J.G. Fleming.  Representing Low Frequency, Spatially Varying Water Level Anomalies in Storm Surge Computations.  2017 American Meteorological Society Annual Meeting.  [https://ams.confex.com/ams/97Annual/webprogram/Paper316033.html Link to talk]</ref>, Asher et al. 2018<ref name="asherPres2018">Asher, T.G., R.L. Luettich, J.G. Fleming, B.O.Blanton.  Assimilation of Observed Water Levels into Storm Surge Model Predictions.  2018 American Meteorological Society Annual Meeting.  [https://ams.confex.com/ams/98Annual/webprogram/Paper334044.html Link to talk]</ref>) and a journal article (Asher et al. 2019<ref name="asher2019">Asher, T.G., Luettich Jr., R.A., Fleming, J.G., Blanton, B.O., 2019. Low frequency water level correction in storm surge models using data assimilation. Ocean Modelling 144, 101483. https://doi.org/10.1016/j.ocemod.2019.101483</ref>) with details and an application to Hurricane Matthew.  Users looking for ways to generate water level correction surfaces can look to that same article and this digital publication/data repository<ref>Asher, T., 2019. Hurricane Matthew (2016) Storm Surge and Wave Simulations with Data Assimilation. https://doi.org/10.17603/2Z8H-7K90</ref>, which holds the code base used in the aforementioned paper.


== Version ==
== Version ==
{{ADC version|version=55: Technical Preview|relation=+}}  
{{Version support box|version=55|relation=+|support=tp}}  
This is considered a technical preview in version 55. Theoretical work is still ongoing.  
This is considered a technical preview in version 55. Theoretical work is still ongoing.


==Controlling Dispersive Behavior==
==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:<br/>
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):<br/>
<code>&AliDispersionControl CAliDisp=T, Cs=1500.0, Ad = 0.0050189, Bd = 0.23394/</code>
<code>&AliDispersionControl CAliDisp=T, Cs=1500.0, Ad = 0.0050189, Bd = 0.23394/</code>


* <code>CAliDisp</code> logical flag to turn Ali's dispersion correction on (F=false by default).  
* <code>CAliDisp</code> logical flag to turn Ali's dispersion correction on (F=false by default).  
* <code>Cs</code> is the speed of sound in water [m/s] for the Mach number based dispersive correction. Set Cs to a negative value to turn this component off.  
* <code>Cs</code> 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.  
* <code>Ad</code> the power law constant.  
* <code>Ad</code> the power law constant.  
* <code>Bd</code> the power law exponent.
* <code>Bd</code> the power law exponent.
For the following equation:
<math>Correction = 1 - \frac{Ma^2}{4} - {A_d}H^{B_d}</math>
where Ma is the Mach number (<math>Ma = \frac{\sqrt{gH}}{Cs}</math>) and H is the total water depth.

Latest revision as of 17:46, 10 July 2020

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

ADCIRC version: 55
Tech Preview

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:

where Ma is the Mach number () and H is the total water depth.