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How to run CESM with land use data fixed for a given year?

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How to run CESM with land use data fixed for a given year?


Although CESM2.0 has not been released yet, we are starting to set up some simulations with a test version of it. The reason is that we need to complete some testing so that we are almost ready to set-up and run some preindustrial millenial CESM-WACCM simulations (for the 850-1850 period) as soon as CESM2.0 is released.

For this we are modifying a BW1850 compset (1850_CAM60%WCTS_CLM50%BGC ...). The lnd_in file of our case has the following for the time varying landuse data file, which causes the land-use types of the initial surface dataset to vary over time:

  flanduse_timeseries = '/glade/p/cesmdata/cseg/inputdata/lnd/clm2/surfdata_map/'

It would be great to have transient forcings both for atmosphere and land during the whole simulation period, but I believe it will take some time until there is any 850-1850 lan-duse file available. We are neither land modellers nor familiar with CLM, so we do not intend to create it. Considering that our main focus is not on land use changes, an acceptable option for us would be to have landuse data fixed to 1850 during the whole simulation period. So we have done as follows:

We have replicated 1850 data (i.e. first time record) from the file above for every single year in the whole 850-1850 period. We have splitted the data into four different files (each one covering a 250-year period) to avoid ending up with very big files. This is obviously not very efficient, as we will be reading big files which include the same data for every year and we will also have to change them every 250 years.

Can somebody tell me if it is really necessary to do this? Is there any other way to force the model to use fix 1850 landuse data, i.e. to read only one time record instead of the big files we have created?

Thank you very much in advance,


Carlos Ordóñez
Universidad Complutense de Madrid (UCM), Spain


maybe this helps:

"As a special case, when the time dimension of the landuse.timeseries dataset starts at a later year than the current model time step, the first time slice from the landuse.timeseries dataset is used to represent the current time step PFT and CFT fractional area distributions."



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