Update readme with UFS module file info

and remove most of the Ubuntu instructions

README.md

@@ -23,15 +23,19 @@ pre-commit install --install-hooks
 
 ### Setup
 
-#### NOAA Hera
+#### Supported UFS machines
 
-Use the official setup.
+UFS spack-stack module files are included for Hera, WCOSS2, Orion, etc.
 ```
 module use ./modulefiles
-module load hera.intel
 ```
 
-Input data:
+Then, on Hera, for example:
+```
+module load ufs_hera.intel
+```
+
+Hera input data:
 ```
 /scratch1/NCEPDEV/rstprod/nexus_emissions
 ```
@@ -41,6 +45,7 @@ Input data:
 
 #### GMU Hopper
 
+Custom modules.
 ```
 . /groups/ESS3/zmoon/nexus/env5
 ```
@@ -52,58 +57,10 @@ Input data:
 
 #### Ubuntu
 
-Tested with Ubuntu 22.04.
-Using GCC v12 available via `apt`.
-
-Dependencies:
-```bash
-sudo apt install build-essential gfortran-12 libnetcdf-dev libnetcdff-dev liblapack-dev libopenblas-dev mpi-default-dev mpi-default-bin
-```
-
-Build ESMF and prepare for NEXUS build:
-```bash
-v="8.3.1"  # ESMF
-gcc="12"
-esmf_base=$HOME/esmf
-
-export ESMF_DIR=${esmf_base}/${v}-gcc-${gcc}
-cd $esmf_base
-mkdir -p $ESMF_DIR
-wget https://github.com/esmf-org/esmf/archive/refs/tags/v${v}.tar.gz
-tar xzvf v${v}.tar.gz --directory=/tmp && mv /tmp/esmf-${v}/* $ESMF_DIR
-
-export ESMF_COMPILER=gfortran
-export ESMF_LAPACK=netlib
-export ESMF_COMM=mpi
-export ESMF_PIO=internal
-export ESMF_NETCDF=nc-config
-
-export OMPI_FC=gfortran-${gcc}
-export OMPI_CC=gcc-${gcc}
-export OMPI_CXX=g++-${gcc}
-export ESMF_F90COMPILER=mpifort
-export ESMF_CCOMPILER=mpicc
-export ESMF_CXXCOMPILER=mpic++
-export ESMF_F90LINKER=/usr/bin/ld
-export ESMF_CLINKER=/usr/bin/ld
-export ESMF_CXXLINKER=/usr/bin/ld
-
-cd $ESMF_DIR
-make lib
-
-# Location of the corresponding `esmf.mk` is needed for CMake to find the lib later
-# You can find these with, e.g., `find . -name 'esmf.mk' -exec realpath {} \;`,
-# but it should be the following:
-ESMFMKFILE=${ESMF_DIR}/lib/libO/Linux.gfortran.64.mpi.default/esmf.mk
-
-# For NEXUS
-export CMAKE_Fortran_COMPILER=$ESMF_F90COMPILER
-```
-
-To build NEXUS, at least these env vars should be set:
-- `ESMFMKFILE`
-- `OMPI_FC`
-- `CMAKE_Fortran_COMPILER`
+See https://github.com/zmoon/gha-esmf for examples of how to build ESMF,
+or follow the steps to download and use a pre-built ESMF.
+
+Remember to set `ESMFMKFILE` to point to the `esmf.mk` file of your ESMF build.
 
 ### Build