carbon flux/pool units in cndv

[ckcastillo@purdue_edu]

Hi Sam,

I just want to verify, is the m^2 unit in the carbon fluxes and pools in clm4-cndv (e.g. NEE, respiration in gC/m2/s, totecosysc in gC/m2) refers to per m^2 of the grid cell area rather than of the veg area or pft area (as opposed to dgvm in which productivity was reported over pft area but heterotrophic respiration was over veg area)?

This is for the purpose of totaling carbon pools and fluxes over a specified region. The code of the diagnostic package seems to use only landfrac and garea in calculating global totals which indicates to me that the m^2 unit refers to the gridcell areas as weighted by landfrac.

CN also seems to use the same units whether reporting total column, pft, etc. carbon, and its code directly subtracts, say AR from GPP to get NPP without any conversion of units, so I would assume they have been "generalized" to be per m^2 of the grid cell.

Thanks,
Kendra

 

[slevis]

I believe that your assumptions are correct.

To give you a definitive answer, I would need to look in the histFlds routine. There you can see what is done to each variable. E.g., some variables may not include special landunits, or specifically lake or urban areas in the gridcell avg. In such cases, the right way to calc. a regional avg would be to remove lake or urban or special landunit areas from the grid cell area. However, I'm not sure that people do that (including the clm diag. pkg as you point out), nor that it makes a big difference in the results. It prob. depends on the situation.

Sam