GeoClaw’s Use of Storm Radius for Storm Surge Simulation

[Mobina Namvar]

Hello everyone,

I’m seeking some clarification on how GeoClaw uses the storm radius(radius of the last closed iso-bar) for storm surge simulation in its computations. 

Based on my understanding of the Fortran code, the storm radius is utilized in the ramping function, which follows this formula:

 R(r)=0.5(1-tanh((r-storm radius)/ramping_width)

Then, R(r,t) is applied to the wind and pressure fields. For instance for wind field: W(r)=W(r)×R(r) 

Is my understanding correct? Additionally, are there any other aspects of GeoClaw where the storm radius is used that I might be missing?

Thanks in advance for your insights!

Best regards,

Mobina

[Kyle Mandli]

Hi Mobina,

That's exactly right.  

If that parameter is not provided we often just set it to something relatively large, such as 500 km.  The wind parameterization used has some impact on how important this is, i.e. whether the tail of the wind field decays quickly.

Kyle

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[Mobina Talebinamvar]

Hi Kyle,

Thank you for confirming! I understand now why you'd set the parameter to 500 km when it's not provided. It makes sense that the wind parameterization would influence how critical that choice is. I'll keep that in mind as I move forward with the simulations.

Thank you again for your helpful answer,
Mobina