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Process for modifying landcover data?

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G

gabriel_bromley

New member
What would be the best process for modifying the land cover data? I would like to change gridpoints from Ag to Barren (simulating an unplanted field). Should I modify geo_em.nc variables for land use fraction and dominant land use? Is there a better way to do this? I am using Noah-MP(dveg=2) and 4km WRF.

Thanks!

Gabe
 
Gabe,
You can modify either geo_em.nc or wrfinput_d01. Note that land use change may also be related to other variables like vegetation fraction, leaf area index, etc. If you set rdlai = .false., then LAI will be derived from the VEGPARM.TBL based on the land use type. This will make things less complicated. However, vegfra (in wrfinput) or greenfrac (in geo_em) needs to be changed if land use is changed.

NCL or the utility we provide can be used to modify the variables.
For NCL, you can find the example here: https://www.ncl.ucar.edu/Applications/change_netCDF.shtml
For WRF utility, please go to: http://www2.mmm.ucar.edu/wrf/users/utilities/util.htm, where you can click read_wrf_nc and find how to use it to change variables in netCDF file.
 
Hi Ming,

I changed the wrfinput but the changes don't propagate through the model. I have sst_update=1. Does this mean I should change every time step of that file? Otherwise if I change land use in the geo_em file, will the LAI and VEGFRA from wrflowinput override these changes?

Thanks,

Gabe
 
Gabe,

If you set set_update =1, then time varying ST and SEAICE from met_em and month LAI/ALBEDO from static WPS input data will be included in wrflowinp. These variables will be updated during your integration. In this case, they will remain the same as the values from static and met_em data and won't change following your changes of landuse type. I believe this is the reason why you don't see changes in the simulation even if you have changed the land use type.

In addition, noahMP is pretty complicated and you need to look at the options used for this scheme (e.g., dveg). How the model processes LAI and VEGFRA is dependent on this option.
 
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