Constant depth below sea level

[Diego1991]

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Hi,

I am using OpenDrift and ROMS to simulate the path of a subsurface drifter moving at a constant depth of 3 m below sea level, and then compare with the observed trajectory. It is possible to use seed_elements(z=-3) but I was wondering if this is a constant depth relative to the mean sea level z=0 or if it is a fluctuating depth relative to the sea level affected by tides. The latter would be the desired behavior for this case. Is there something like z='surface-3' as there is for the seafloor?

Also, the ROMS has the vertical component w in it, but I would like to prevent the elements from moving vertically for this case. I was planning planning to use the 3-D OceanDrift module but there may be a better choice. If not, after creating the ROMS reader, can I deactivate w?

Your help is much appreciated. Thank you, Diego

[knutfrode]

Hi,

(I thought I had answered this one before, but cannot find it, thus answering again just in case...) Presently, z is always relative to mean sea level. However, you may add sea_surface_height_above_mean_sea_level (or similar) as a required variable to your module. Then it should be a straightforward update inside your update method to make sure particle depths (self.elements.z) are relative to this, and not mean sea level.

Regarding disabling vertical motion, see this issue: https://github.com/OpenDrift/opendrift/issues/909