Most of the imbalance is in the European region where most of the wood thinning is occuring in the early historical period (1850’s).
Time series of global sums
Cumulative
There is a large imbalance at the start of the simulation of 3.5 Pg(C). This comes from Evergreen needle leaf and Evergreen broad leaf. However after 50 years C3 grass becomes the larger source of the imbalance.
Absolute and relative values at a single grid point
Looking at a specific grid cell in the hot spot in Europe, the NBP is too low compared to the ΔCpools, and for this location the responsible PFTs are Evergreen needle leaf and deciduous broad leaf.
The imbalance is usually about 80% of the NBP but at the start it is >1.5x.
So carbon does not seem to be conserved in this simulation and the wood thinning is likely responsible. Perhaps the additional wood flux from thinning isn’t being added to the fluxes? WIll have to dig into the code.
The wood thinning forcing data in the previous post is far too high. The area in the raw LUH2 files for thinning is only half that above. I think this is probably caused by improper regrinding to ACCESS resolution. There is also a lot of data missing below 25 degrees north.
I have reprocessed the thinning data (LUH2’s primf_harv + secmf_harv + secyf_harv) using cdo’s remapcon2 function to conserve area and mapped this onto ACCESS’s cover fractions to create a new forcing dataset. Rerunning with the new forcing data gives the NBP in the blue line, the orange line is the NBP from new forcing but also with initial wood harvest pools:
This looks like an improvement. Of course, this could all change when we get new land use change forcing data for CMIP7.
There still remains the question about what is the primf_harv variable is and how is it different to the wood harvest that would occur from a transition from primary forest to secondary forest. If thinning occurs on primary forest, it is no longer primary forest. ACCESS doesn’t make any distinction between the two currently, so I don’t think it’s a big issue now, but it will be when CABLE 4 incorporates POP.
@tammasloughran, thanks for the update.
What is the relative magnitude of primf_harv, secmf_harv, secyf_harv? I wonder if primf_harv shouldn’t be included in the thinning because there is the potential to double-count tree removal - though maybe only partially - if forest goes to non-forest but not if primary forest goes to secondary forest. Having said that, if we later clear that secondary forest (even though ACCESS doesn’t know it is secondary), we would then be potentially double-counting presumably against the secmf_harv or secyf_harv??
primf_harv is a fairly large chunk of the harvest for most of the historical period, but in the latter part of the historical it’s mostly secondary young forest.
To find out what primf_harv, secyf_harv and secmf_harv in LUH2 are, I found a paper for the Ecosystem Demography model (in the sup. material) that uses these variables. In that model, they are treated as “harvest transitions”, i.e. transition from primary vegetation to secondary vegetation, or secondary vegetation to secondary vegetation. In these cases the transition is from a forest to a forest, which I guess does not involve completely clearing the land. The other type of transition are “clearing transitions” from forest to non-forests. Interestingly, they also include secnf_harv in their harvest transitions, but in the context of ACCESS, I don’t know what this would correspond to. Crop harvest/grazing? Whatever it is, I exclude it. So I think the three variables I have used are correct.
Can someone who has permission to p66 and /g/data/access please copy /g/data/p66/tfl561/thinning/harvest_frac/cable_thinning_frac_1850-2015.nc to /g/data/access/payu/access-esm/input/historical/atmosphere
? Perhaps @ben , since i think you have worked on things related to modifying UM restart files? Is this a good location?
Aidan
(Aidan Heerdegen, ACCESS-NRI Release Team Lead)
29
If this is something that is required for ACCESS-ESM1.6 then we should copy it to /g/data/vk83.
@spencerwong would be the right person to talk to about this.
In /g/data/vk83 we have a directory for ESM1.6 inputs that’s being populated as data comes in (/g/data/vk83/configurations/inputs/access-esm1p6) – as @Aidan mentioned this is probably the best place for it to go.
There’s not currently much in this directory, but it’s structure will likely match the directory for the ESM1.5 inputs (/g/data/vk83/configurations/inputs/access-esm1p5/), e.g:
I just had a couple of quick questions to make sure it goes to the right place:
Would the wood thinning data match either of the categories biogeochemistry or vegetation? If not we can add a new one.
Is the file’s modification date,2024.11.22, suitable for versioning the file?
Would you be happy to put together a brief README file to go along with the data? This could just link to your first post explaining the data source, processing and also the scripts. We don’t yet have a provenance system worked out for the new inputs, but this would be really helpful for us to keep track of.
Would the wood thinning data match either of the categories biogeochemistry or vegetation? If not we can add a new one.
I would say it matched the category vegetation. It is land-use data, therefore it should probably sit with the cover fractions.
Is the file’s modification date,2024.11.22, suitable for versioning the file?
Yes, but I would go further and mention that this is derived from LUH2 in the versioning. Or perhaps just put LUH2 somewhere in the file name. In the future I can create an LUH3 version, but I am still waiting on the LUH3 vegetation cover fractions to be processed for ACCESS, which are needed to map on to the CABLE vegetation types.
Would you be happy to put together a brief README file to go along with the data? This could just link to your first post explaining the data source, processing and also the scripts. We don’t yet have a provenance system worked out for the new inputs, but this would be really helpful for us to keep track of.
Of course. As long as the first post of this thread is a good place for the documentation. /g/data/p66/tfl561/thinning/README.md
Good idea, let me know if /g/data/vk83/configurations/inputs/access-esm1p6/modern/historical/atmosphere/land/vegetation/global.N96/2024.11.22/LUH2_cable_thinning_frac_1850-2015.nc looks suitable for a filename/destination.
The wood thinning inputs have been copied over to /g/data/vk83/configurations/inputs/access-esm1p6/modern/historical/atmosphere/land/vegetation/global.N96/2024.11.22 (thanks to @TommyGatti’s configurations inputs workflow!)
