[MITgcm-support] The pressure gradient term (Um_dPdx & Vm_dPdy) in the momentum equation

[yang zhibin]

Hello, all,


I want to calculate the pressure gradient term in the momentum equation. In fact, I can directly diagnose this term using diagnostics pkg (which is called Um_dPdx & Vm_dPdy). But when I try to calculate this term, I found the result is not similar with the diagnostics output at all. 


My detailed method is as follow:


dPdx=d(PH-PHI_SURF)dx, PH is the direct output from model (in my mind, this term is hydrostatic pressure anomal, the vertical integral of rho-rhoconst), PHI_SURF is a diagnostics term which mean surf pressure (like g*eta).


I am not sure where is wrong of this calculation. So could anyone help me? Thanks a lot.


Cheers,


Yang
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