Inconsistency between the number of land use types in the available data and the number of land use types in the CLM

[CGL]

Hi,all!

We have focused on the output of the GCAM model under future scenarios, but the land use types output in GCAM are mostly aggregated. For example, in CLM vegetation is classified into a total of 16 categories, but in the GCAM outputforest is only distinguished into 5 categories(AR6 database). Forests in AR6 are divided into Harvested Areas,Natural Forest,managed forest, Afforestation and reforestation.

I understand that different parameter settings exist for different vegetation types in the CLM, e.g. albedo, phenological period. What do I need to do to change those aggregated data to standard input data in CLM?

Thanks!

 

[lawrencepj1]

Hi CGL

For the future CMIP6 scenarios used by CESM and CLM5 the land use from each IAM was translated and harmonized into the CMIP6 LUH2 data format from the native products:

https://luh.umd.edu/

To use this data in CESM the LUH2 is translated into annual time series of CLM5 plant and crop functional types along with fertilizer, irrigation and wood harvest. Details of the process of going from CMIP6 LUH2 data to CLM5 surface data are detailed in the CLM5 Land Data Technote which can be found at:

GitHub - lawrencepj1/CLM5-Land-Data-Technote: This is the working documentation for the CLM5 Land Data

This is the working documentation for the CLM5 Land Data - lawrencepj1/CLM5-Land-Data-Technote

github.com

Other researchers have been working on methods to directly generate CLM5 land use data from GCAM. One particular project is at the DOE Pacific Northwest National Labs through the Integrated Multisector Multiscale Modeling project.

Integrated Multisector Multiscale Modeling

Innovative modeling to explore how human and natural system landscapes in the United States co-evolve in response to short-term shocks and long-term influences

im3.pnnl.gov

I would suggest following up on this method as it would be the easiest option as you would not need to generate the LUH2 data prior to generating CLM5 data.

Cheers
Peter

 

[CGL]

Thanks,Peter! I'm also currently trying to downscale with the Demeter tool. But the problem still exists, the land use type categories output by GCAM do not contain the land use type categories in CLM.

I would like to know how this type of problem is handled in CLM? How do you convert to LUH2 standard files? I don't seem to see weights assigned

 

[lawrencepj1]

Hi CGL

For the LUH2 data we have grid cell specific time dependent PFT and CFT profiles for each LUH2 class. These profiles are generated from current day MODIS and other global land surface products LP DAAC - Homepage combined with climate dependent potential vegetation data. The annual crop functional type distributions are determined from the global EarthStat map product for the year 2000 EarthStat - GIS data for agriculture and the environment combined with the UNFAO Stat country level data for 1961 - 2016 Statistics | FAO | Food and Agriculture Organization of the United Nations.

Cheers
Peter

 

[CGL]

Hi Peter!

I would like to know how to produce land use data for 2015-2100 for the SSP scenario. Because I see that there are 64 PCT_CFTs and 15 PCT_NAT_PFTs in landuse.timeseries_0.9x1.25_SSP1-1.9_78pfts_CMIP6_simyr1850-2100_c190214 alone. There doesn't seem to be so many types of landclasses output from GCAM or LUH2 in 2015-2100.

So how is the change in area of the different landclasses in 2015-2100 calculated?CLM5 tech note I can't seem to find a detailed tutorial on this.

Regards
Goolong