Manning's N Values for RTM, CESM-LME

[Kamm23]

I have been using Land Use Harmonization^2 data (https://luh.umd.edu/) in order to create a visual of land use land change over the last thousand years. I have been looking at pasture, range, non-forested/forested land, c3/c4 crops, and urban (units are fraction of grid cell).

I was told that the CESM water routing model uses a simplified version of manning’s equation to calculate water flux - does anyone know of a dataset or technote that includes the manning's n values associated with CLM5 surface data or LUH2 data?

 

[oleson]

I think the Manning n values are part of the MOSART frivinp_rtm file found in mosart_in:

frivinp_rtm = "/glade/p/cesmdata/cseg/inputdata/rof/mosart/MOSART_routing_Global_0.5x0.5_c170601.nc"

double nr(lat, lon) ;
nr:units = "unitless" ;
nr:long_name = "Manning\'s roughness coefficient for main channel flow" ;
nr:_FillValue = -9999. ;
nr:coordinates = "latixy longxy" ;
double nt(lat, lon) ;
nt:units = "unitless" ;
nt:long_name = "Manning\'s roughness coefficient for tributary channel flow" ;
nt:_FillValue = -9999. ;
nt:coordinates = "latixy longxy" ;
double nh(lat, lon) ;
nh:units = "unitless" ;
nh:long_name = "Manning\'s roughness coefficient for overland flow" ;
nh:_FillValue = -9999. ;
nh:coordinates = "latixy longxy" ;

MOSART is briefly described in the CLM5 technical note:

2.14. Model for Scale Adaptive River Transport (MOSART) — ctsm release-clm5.0 documentation

More information is probably available in the papers by Li et al. cited in the technical note.

 

[Kamm23]

Thanks! I'll take a look

 

[Kamm23]

Hello. I've read through the tech note, as well as the Li et al and Getirana et al papers. I see there is only mention of spatial distribution and there are no time dimensions for the Manning's n values in the file mentioned above. Are the n values assumed to be constant when running model simulations over long time periods?

 

[oleson]

Yes, that is my assumption as well.