Changing Land Ice

The land model in CCSM3 is the Community Land Model 3.0 (CLM4).  The CLM requires a surface dataset that defines the spatial distribution of vegetation, surface water, and land ice.  Some near-modern simulations are able to use the present day (default) surface dataset

However, if you want to make changes to your land cover (e.g., by adding/removing land ice or by changing vegetation), you will need create a new surface dataset to reflect these changes.  The surface dataset requires 'raw' data at 0.5 degree grid resolution netCDF files called 'mksrf' files.  These data define the spatial distribution of vegetation types (PFT), inland lakes, and land ice data for the land model. 

convert_mksrf

If your experiment requires a change in land ice, we provide a tool called convert_mksrf.F90  that will modify the default mksrf files to reflect land surface changes in glaciers, lakes/wetlands, and PFTs and produce new mksrf_glacier_myrun.nc, mksrf_lanwat_myrun.nc and mksrf_pft_myrun.nc files.  The program requires a netcdf file containing your surface variables at 10min resolution.  If you have added land and/or land ice over ocean grid cells (e.g., Fenno-Scandia, Hudson Bay) you will also need to create new coupler mapping files to reflect the change to the land/sea mask.

If your experiment requires a change in land ice, we provide a tool called convert_mksrf.F90  that will modify the default mksrf files to reflect land surface changes in glaciers, lakes/wetlands, and PFTs and produce new mksrf_glacier_myrun.nc, mksrf_lanwat_myrun.nc and mksrf_pft_myrun.nc files.  The program requires a netcdf file containing your surface variables at 10min resolution:

Tool:  convert_mksrf.F90

 

filenameresolution
Input: topography/ice 10min
Output:    
  mksrf_lanwat.myrun.nc 0.5o
  mksrf_pft.myrun.nc 0.5o
  mksrf_glacier.myrun.nc 0.5o

 

Usage: 

  1.  cp convert_mksrf.template convert_mksrf.template.myrun 
  2.  modify convert_mksrf.template.myrun to point to your input files 
  3. cp convert_mksrf.template.myrun convert_mksrf.F90
  4.  compile (gmake)
  5.  execute:  ./convert_mksrf

 

Input File format for convert_mksrf.F90

 

        float TOP(lat, lon) ;

                TOP:units = "meter" ;

                TOP:long_name = "10-min elevation from USGS 30-sec dataset" ;

        float lat(lat) ;

                lat:long_name = "lat" ;

                lat:units = "degrees north" ;

        float lon(lon) ;

                lon:units = "degrees east" ;

                lon:long_name = "lon" ;

        float ICE(lat, lon) ;

                ICE:units = "%" ;

                ICE:long_name = "Fraction of Grid Cell Covered with Glacier" ;

                ICE:valid_min = 0.f ;

                ICE:valid_max = 100.f ;

        float LANDFRAC(lat, lon) ;

                LANDFRAC:units = "meter" ;

                LANDFRAC:long_name = "10-min elevation from USGS 30-sec dataset" ;

                LANDFRAC:valid_max = 1 ;

                LANDFRAC:valid_min = 0 ;

        float LANDMASK(lat, lon) ;

                LANDMASK:units = "meter" ;

                LANDMASK:long_name = "10-min elevation from USGS 30-sec dataset" ;

                LANDMASK:valid_max = 1 ;

                LANDMASK:valid_min = 0 ;