TEND data in history file

[abardin]

We are running an independent version of MARBL that is based on the X3 v2.2.0, and trying to validate some of the data received from MARBL.
In the history files, we see items such as TEND_PO4 and RF_TEND_PO4. How do these relate to the tendencies returned by MARBL?

 

[mlevy]

Hi Ann,

TEND_PO4 is the total tendency term, computed by directly comparing the tracer values from the previous time step (or steps) to the latest time step. In the most simplistic terms, it's (PO4(i,j,k,t) - PO4(i,j,k,t-1))/dt; for the 3 degree grid, where we still rely on the leapfrog time-stepping scheme, it's (PO4(i,j,k,t+1) - PO4(i,j,k,t-1))/(2*dt). (There are some additional terms to account for changes in the surface layer thickness that are computationally important but more of a distraction for a general explanation of the term.) The 1 degree grid uses the Robert filter when time-stepping, and RF_TEND_PO4 is just the contribution of the Robert filter to the total tendency.

~Mike

 

[abardin]

Thank you, Mike.