npp diagnostics are incorrect

[aekiss]

As noted in hrsdawson/ACCESS-WOMBAT_01deg_BGC_validation#3 (comment), the diagnostic npp3d is calculated incorrectly (it's phytoplankton growth (f11) minus grazing (f21), but should be phytoplankton growth minus linear mortality (f22)).

MOM5/src/mom5/ocean_csiro_bgc/bio_v3.inc

Lines 347 to 348 in 5126b54

	! Net primary productivity (gross PP minus linear mortality)
	npp3d(i,j,k) = npp3d(i,j,k) + dtsb*(f11 - f21)

We could fix this by replacing f21 (grazing) with f22 (linear mortality).

[aekiss]

This bug also affects the diagnostics that are derived from npp3 (npp1, npp2d, npp_intmld, npp_int100)

[aekiss]

@hakaseh should I fix his while we're at it?

[hakaseh]

yes, I thought about that too.
Based on the discussion from COSIMA/access-om2#272, should we consider pprod_gross as NPP ?