Add optional Vstretching parameter to zlevs.m and zlevs_1d.m#2
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loganchal wants to merge 1 commit intoSAEON:masterfrom
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Add optional Vstretching parameter to zlevs.m and zlevs_1d.m#2loganchal wants to merge 1 commit intoSAEON:masterfrom
loganchal wants to merge 1 commit intoSAEON:masterfrom
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The vertical stretching function (Vstretching) was previously hardcoded: vtransform=1 always used Song & Haidvogel (1994), and vtransform=2 always used csf() (Shchepetkin 2010). This broke compatibility with ROMS output files using other Vstretching values, particularly Vstretching=5 (Souza et al., 2015 quadratic Legendre polynomial), used by e.g. the Moana Hindcast (Vtransform=2, Vstretching=5). Changes: - Add optional 9th argument 'vstretching' (1-5) to zlevs.m and zlevs_1d.m - Fully backwards compatible: existing 8-arg calls produce identical results - Emit warning when vtransform=2 and vstretching is not specified, to alert users who may be reading ROMS files with non-default stretching - Support all 5 ROMS vertical stretching functions inline (no new deps) - Remove csf() dependency (formulas computed inline) - Fix redundant w-point loop computation - Remove dead commented-out debug code References: - Song & Haidvogel (1994), J. Comput. Phys., 115, 228-244 - Shchepetkin & McWilliams (2005), Ocean Modelling, 9, 347-404 - Souza et al. (2015), J. Phys. Oceanogr., 45, 424-440 - https://www.myroms.org/wiki/Vertical_S-coordinate
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Summary
vstretching(1–5) tozlevs.mandzlevs_1d.m, supporting all 5 ROMS vertical stretching functionsvtransform=2andvstretchingis not specified, alerting users who may be reading ROMS files with non-default stretching (e.g. Vstretching=5)Motivation
The vertical stretching function was previously hardcoded:
vtransform=1always used Song & Haidvogel (1994), andvtransform=2always usedcsf()which implements Shchepetkin (2010) — equivalent to Vstretching=4. This broke compatibility with ROMS output files using other Vstretching values, particularly Vstretching=5 (Souza et al., 2015 quadratic Legendre polynomial), used by e.g. the Moana Hindcast (Vtransform=2, Vstretching=5).Changes
zlevs.m: Add optionalvstretchingparameter with all 5 stretching functions computed inline. Removescsf()dependency. Fixes redundant w-point loop. Removes dead commented-out debug code.zlevs_1d.m: Same changes for the 1D variant.Supported Vstretching values
See: https://www.myroms.org/wiki/Vertical_S-coordinate
Backwards compatibility
Calling
zlevs(h, zeta, theta_s, theta_b, hc, N, type, vtransform)with 8 arguments works exactly as before. The only new behavior is a warning whenvtransform=2is used without specifyingvstretching, since the default (4) may not match the ROMS file.