Dear all, I'm trying to get output of our 3D hydrodynamic model into a CF compliant NetCDF file. The vertical coordinates satisfy the ocean_sigma_coordinate conventions with one caveat.
The ocean_sigma_coordinate formula terms http://cfconventions.org/cf-conventions/cf-conventions.html#_ocean_sigma_coordinate are "sigma: var1 eta: var2 depth: var3". Given the formula z(n,k,j,i) = eta(n,j,i) + sigma(k)*(depth(j,i)+eta(n,j,i)) I conclude that the depth should here be interpreted as the depth below the reference plane since eta+depth seems to refer to the total water depth. In our model output we write the * water depth, i.e. depth+eta, and the * bed levels (positive up), i.e. -depth, because we don't use this model only for oceans but also for other flooded parts of the earth surface and writing depth (positive down) is extremely inconvenient for those applications So, now the question arises: how to store the vertical coordinates. Do we need to introduce an adjusted ocean_sigma_coordinate version (and possibly other formulae as well) or do you see an easier work around, e.g. * use depth: to point to a var3 defined with positive defined upward, * allow a variant with different 3rd keyword to indicate that the var3 is defined positive upward While looking into this issue, I realize that the CF formulations are somewhat confusing since depth refers here to the the depth below the reference plane whereas the standard name "depth" refers to the "depth is the vertical distance below the surface". Best regards, Bert DISCLAIMER: This message is intended exclusively for the addressee(s) and may contain confidential and privileged information. If you are not the intended recipient please notify the sender immediately and destroy this message. Unauthorized use, disclosure or copying of this message is strictly prohibited. The foundation 'Stichting Deltares', which has its seat at Delft, The Netherlands, Commercial Registration Number 41146461, is not liable in any way whatsoever for consequences and/or damages resulting from the improper, incomplete and untimely dispatch, receipt and/or content of this e-mail.
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