wiki:CarbonCycleUnits

Version 6 (modified by smoreira, 6 years ago) (diff)

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Units and Scale Factors in the Carbon Cycle Model

Variables units in OCYCC. Six and Maier-Reimer, 1996.

The main variables in the OCYCC (Carbon Cycle Model in iLOVECLIM) are ODIC, OALK, OPO4, ONO3, OO2, ODOC, ODOCS, OC13, OC14, ODOC13, ODOCS13. Particles include CaCO3 (calcite) and TPP (Total Particle Production). Another two important secondary variables are phyto_m and zoo_m, i.e. phytoplankton and zooplankton, which are really important in the intermediate calculations of DIC and DOC, for example. All these variables must be checked in terms of units and consistency of equations, units and scale factors.

Six and Maier-Reimer (1996)

Six and Maier-Reimer (1996) describes some of the base equations of teh NPZD model used in OCYCC/iLOVECLIM. More precisely, most of the equations presented in this manuscript regarding phytoplankton and zooplankton dynamics can be found in mbiodyn.f.

Table 1 in Six and Maier-Reimer (1996) shows parameter values for the phytoplankton and zooplankton equations which mostly coincide with the parameter definitions present in initmbiopar.f (if not with the same value, a very similar one). For example, half-saturation constant for nutrient uptake is in both cases 0.016 µmolC×L-1 or minimum phytoplankton concentration, which is set in both cases, publication and OCYCC code to 0.01 µmol×L-1

A similar example can be tested in the case of zooplankton. Half-saturation constant for phytoplankton ingestion is in Six and Maier-Reimer (1996) equal to 4 µmol×L-1 and similar to the value used in OCYCC 3.5 µmol×L-1, which can be found in initmbiopar.f

Those parameters and many others related to phytoplankton and zooplankton dynamics prove that the same equations are used in both cases and, therefore, units of the main variables must be the same. This means that units for phytoplankton and zooplankton are µmol×L-1 or µmol×kg-1, assuming an averaged density value of 1 kg×L-1

Some of the variables used in the phytoplankton and zooplankton equations in Six and Maier-Reimer (1996), such as exudation or mortality of phytoplankton and excretion of zooplankton are also part for POC (Particulated Organic Carbon) or TPP (all particles that stem from natural senescence of feval pellet production within the euphotic layer summarized as Total Particle Production), as we can see, for example, in page 563.

This expression fully coincides with line 293 in file mbiodyn.f' where variable TPP_diff' is defined. Therefore, TPP_diff must be also expressed in µmol×kg-1. Some times the parameters in OCYCC code coincide with the values presented in Six and Maier-Reimer (1996) but divided by TDAY. This is due to the fact that mbiodyn and maphot subroutines are called in mbiota.f inside of a loop, because these calculations are performed in several iterations per day in the loop, do itime = 1, itimemax

Inorganic Carbon Equilibrium for Climber, subroutine incche

Scale factors for unit conversion in OCYCC

mbiodyn.f & maphot.f, scanu factor

out_ocycc.f & eco2.f, scale_m factor

out_ocycc.f & eco2.f, scale_b factor