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missing parenthesis in Nitrogen burial fraction #26

Closed sditkovsky closed 1 year ago

sditkovsky commented 1 year ago

Hello,

We were looking into Nitrogen burial in COBALT and were puzzled by line 7810:

cobalt%frac_burial(i,j) = 0.013 + 0.53*fpoc_btm**2.0/((7.0+fpoc_btm)**2.0) * & cobalt%zt(i,j,k) / (cobalt%z_burial + cobalt%zt(i,j,k))

Is the a missing set of parenthesis in the numerator?

Best, Sam and Fan

jessluo commented 1 year ago

Hi Sam and Fan,

Thanks for raising this issue.

Looking at the code, I can see that it is definitely ambiguous. It is also not helped by line 7809, which reflects an older bug that was fixed a while ago. We definitely need to remove line 7809 to avoid future confusion.

For this line (lines 7810-7811), it is doing what it is supposed to as it is currently written -- the baseline is 1.3% burial and then burial increases with flux of POC to the bottom (following Dunne et al. 2007), which ramps up as depth increases. Though we agree that the lack of explicit parentheses makes it ambiguous.

Regarding an alternative, both @charliestock and I are open to an alternative formulation if after scientific evaluation, you guys (Resplandy lab) think that the 1.3% should also be subject to the depth-based ramp. In reality, the number of grid cells where the depth is very shallow and flux of POC to the bottom is zero is likely to be minimal, but if changing the parentheses improves the model representation of burial in shallow coastal areas, then let us know and we can discuss.

thanks, Jessica