[MITgcm-support] Tidal forcing at the open boundaries

[Ruan Xiaozhou]

Dear MITgcm users,

This might be an old question (I couldn’t find a satisfying answer in the old posts though). I’m trying to force a nested patch with tidal forcing at the open boundaries using the OBCS package. However, the required tidal amplitude and phase input files have some weird units that confused me. In the OBCS_PARAMS.h file, it specifically says the ‘amplitude’ should have the unit of m/s and the ‘phase’ should have the unit of second. I guess maybe it makes sense for the ‘phase' if it is defined as ph * T/(2 pi) where T is the tidal period and ph is what I have from normal tidal output dataset (e.g. TPXO) that has the unit of radian. But the amplitude input is directly used to add to both velocities (u and v) at the open boundaries but it normally has the unit of meter in tidal datasets. I was wondering if anyone could share their experience converting the units of these tidal input files? 

Thanks for your time.

Cheers,
Xiaozhou