January 30th
@RachelLaw likely an apology again - sorry.
For discussion
Vegetation distribution. If you want to look at the distribution I’ve prepared, there are plots in slides 25-35 of this file:
landuse1850.pdf (1.7 MB)
Left figure on each page is the new vegetation distribution, right plot is the difference from ESM1.5. My aim was to make sure we had sufficient trees to match all of the LUH3.0 forest (=primf+secdf) while also allowing existing ESM1.5 tree fractions to continue in LUH3.0 nonforest (=primn+secdn+range+pastr+urban). I also replaced our existing crop pft (9) with LUH3.0 c3 crop (=c3ann+c3nfx+c3per) and added c4 crop (10) to match LUH3.0 c4 crop (=c4ann + c4per).
Getting the 1850 vegetation distribution matched to LUH3.0 makes mapping changes from 1850 to present relatively straightfoward. The only limitation is that there is no easy way to switch tree types over time e.g. if evergreens were being replaced by deciduous etc.
Questions
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In some cases, I had to arbitrarily choose which tree or grass type to add - I just did this by latitude but perhaps could do something more like POP does in its vegetation type determination. Thoughts?
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Anyone spot any major issues with the new vegetation distribution? There is significantly more forest for high northern latitudes, but switch from Medlyn to Leuning etc has reduced GPP in northern high latitudes so we probably have scope to increase. Also our atmospheric CO2 seasonality at northern high latitudes was rather low for ESM1.5, so this change might improve that.
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Do we want further modify Australia? Do we want to have Australia-specific pft types? Pft 12 and 13 are currently available.
Testing the new vegetation distribution as soon as possible would be great. Information for creating a restart file is here: Modify a UM restart file to work with new vegetation distribution - Earth System / Earth System Model - ACCESS Hive Community Forum.
Any progress?
Notes:
- Discussion on what work is needed on the vegetation distribution for LUH3. Mention of C4 crops - Is it possible to use it in ESM? Need to revisit the parametrisation for C4. Need to check the coding for C4 crops and grasses as it hasn’t been used in some time.
- Priority is to be able to get a test run with the new distribution so we can assess the impact. Need a restart file.
- Should we initialise tiles for all types in all grid cells in the initial restart file and not run through the tiles that are not active. The question is how the landuse change code creates new tiles.
- Should we use Australian-specific PFTs? Belinda has 22 PFTs but we only have space for 2 additional PFTs in CABLE. Could we reclassify any of the 22 PFTs together to have a type that covers a large enough space to be worth the work. @Juergen to ask Belinda.
- POP runs by @Juergen : we need to review what the next steps are.
- Vegetation height: it’s possibly causing instabilities. We may want to change the inputs for the veg. height. To discuss at a future meeting. UKMO does not seem to do better than us, maybe CLM would be useful.
Action
- @Juergen to ask Belinda on PFTs for Australia.