This lesson is still being designed and assembled (Pre-Alpha version)

# Himalaya experiment

## Overview

Teaching: 0 min
Exercises: 0 min
Questions
• How to remove Himalaya mountains?

Objectives
• Learn to remove the Himalaya mountains in a CESM experiment

### Himalaya Mountains: how to update the input dataset?

Copy the original surface geopotential file into your case directory.

On Saga:
``````export EXPNAME=himalaya
cd \$HOME/cases/F2000climo-f19_g17.\$EXPNAME

cp /cluster/projects/nn1000k/cesm/inputdata/./atm/cam/topo/fv_1.9x2.5_nc3000_Nsw084_Nrs016_Co120_Fi001_ZR_061116.nc .
``````

Use nco utilities to edit the values in the file (http://nco.sourgeforce.net). We will use a function called ncap2 – (netCDF Arithmetic Averager) single line command below.

On Saga:
``````module load NCO/4.7.9-intel-2018b

ncap2 -O -s 'lat2d[lat,lon]=lat ; lon2d[lat,lon]=lon' -s 'omask=(lat2d >= 30.0 && lat2d <= 50.0) && (lon2d >=70.0 && lon2d <= 100.0)' -s 'PHIS=(PHIS*(1-omask))' fv_1.9x2.5_nc3000_Nsw084_Nrs016_Co120_Fi001_ZR_061116.nc fv_1.9x2.5_nc3000_Nsw084_Nrs016_Co120_Fi001_ZR_061116_\$EXPNAME.nc
``````

Apply this change.

On Saga:
``````echo "bnd_topo = './fv_1.9x2.5_nc3000_Nsw084_Nrs016_Co120_Fi001_ZR_061116_\$EXPNAME.nc'" >> user_nl_cam

./preview_namelists

grep topo /cluster/work/users/\$USER/cesm/F2000climo-f19_g17.\$EXPNAME/run/atm_in
``````

Copy the modified surface geopotential data file into your run directory.

On Saga:
``````cp fv_1.9x2.5_nc3000_Nsw084_Nrs016_Co120_Fi001_ZR_061116_\$EXPNAME.nc /cluster/work/users/\$USER/cesm/F2000climo-f19_g17.\$EXPNAME/run/.
``````

• Himalaya