Per #2949, updating installation instructions

docs/Users_Guide/installation.rst

@@ -162,18 +162,35 @@ Environment Variables to Run Script
 Before running the compilation script, there are five environment variables
 that are required: 
 **TEST_BASE**, **COMPILER**, **MET_SUBDIR**, **MET_TARBALL**, and **USE_MODULES**.  
+
 If compiling support for Python embedding, the script will need the following
 additional environment variables: **MET_PYTHON**, **MET_PYTHON_CC**, and
-**MET_PYTHON_LD**. All of these environment variables are discussed
-in further detail in the Environment Variable Descriptions section below.
-An easy way to set these environment variables is in an environment
-configuration file  (for example, **install_met_env.<machine_name>**). An
-example environment configuration file to start from (**install_met_env.generic_gnu**),
-as well as environment configuration files used on HPCs at NCAR and NOAA,
+**MET_PYTHON_LD**.
+
+All of these environment variables are discussed in further detail in the
+Environment Variable Descriptions section below. An easy way to set these
+environment variables is in an environment configuration file
+(for example, **install_met_env.<machine_name>**). An example environment
+configuration file to start with (**install_met_env.generic_gnu**),
+as well as the environment configuration files used on HPCs at NCAR and NOAA,
 can be found in the `MET GitHub repository <https://github.com/dtcenter/MET>`_ in the 
 `scripts/installation/config <https://github.com/dtcenter/MET/tree/main_v12.0/internal/scripts/installation/config>`_
 directory.
 
+.. note:
+
+   Starting with MET-12.0.0, the C++17 standard is the default standard for
+   MET, due to the C++17 standard being a requirement for the dependent
+   library, ATLAS, in versions 0.33.0 and greater. The ATLAS library is
+   conditionally required, if support for unstructured grids is desired.
+
+   At this time, users with systems that do not yet support the C++17
+   standard, can still compile MET with an older C++ standard, using an
+   older version of ATLAS, by adding the MET_CXX_STANDARD variable to
+   the environment configuration file as described in the **OPTIONAL**
+   section below.
+   
+
 Environment Variable Descriptions
 ---------------------------------
 
@@ -218,6 +235,7 @@ Environment Variable Descriptions
     following environment variables if using the Intel compilers: 
 
     | For non-oneAPI Intel compilers:
+    |
     | export FC=ifort
     | export F77=ifort
     | export F90=ifort
@@ -226,6 +244,7 @@ Environment Variable Descriptions
 
 
     | For oneAPI Intel compilers:
+    | 
     | export FC=ifx
     | export F77=ifx
     | export F90=ifx
@@ -289,13 +308,13 @@ Environment Variable Descriptions
 
     **export MET_CXX_STANDARD** - Specify the version of the supported
     C++ standard. Values may be 11, 14, or 17. The default value is 17.
-    (e.g. export MET_CXX_STANDARD=11).
+    (e.g. export MET_CXX_STANDARD=11)
 
 
 External Library Handling in compile_MET_all.sh
 -----------------------------------------------
 
-.. dropdown:: IF THE USER WANTS TO HAVE THE COMPILATION SCRIPT DOWNLOAD THE LIBRARY DEPENDENCIES
+.. dropdown:: IF THE USER WANTS TO HAVE THE COMPILATION SCRIPT INSTALL THE LIBRARY DEPENDENCIES
 
     The **compile_MET_all.sh** script will compile and install MET and its
     :ref:`required_external_libraries_to_build_MET`, if needed. 
@@ -399,7 +418,21 @@ particular system’s needs, MET is ready for installation. The screenshot below
 contents of the installation directory followed by the tar_files subdirectory at 
 this step on the machine ‘hera’.
 
-.. image:: figure/installation_dir.png
+.. code-block:: ini
+
+  /contrib/met/12.0.0$ ls
+  compile_MET_all.sh  install_met_env.hera  tar_files
+  
+  /contrib/met/12.0.0$ ls tar_files
+  HDF-EOS2.16v1.00.tar.Z         eckit-1.24.4.tar.gz            netcdf-4.7.4.tar.gz
+  HDF4.2r3.tar.gz                freetype-2.11.0.tar.gz         netcdf-cxx4-4.3.1.tar.gz
+  atlas-0.30.0.tar.gz            g2clib-1.6.4.tar.gz            pixman-0.40.0.tar.gz
+  atlas-0.35.0.tar.gz            gsl-1.11.tar.gz                proj-7.1.0.tar.gz
+  bufr_v11.6.0.tar.gz            gsl-2.7.1.tar.gz               sqlite-autoconf-3430100.tar.gz
+  cairo-1.16.0.tar.xz            hdf5-1.12.2.tar.gz             tiff-4.6.0.tar.gz
+  ecbuild-3.5.0.tar.gz           jasper-2.0.25.tar.gz           zlib-1.2.11.tar.gz
+  ecbuild-3.7.0.tar.gz           jpegsrc.v9e.tar.gz
+  eckit-1.20.2.tar.gz            libpng-1.6.37.tar.gz
 
 Simply enter the following into the terminal to execute the script:
 
@@ -409,13 +442,16 @@ Simply enter the following into the terminal to execute the script:
 
 The screenshot below shows the contents of the installation directory after installation:
 
-.. image:: figure/installation_dir_after.png
+.. code-block:: ini
+
+  /contrib/met/12.0.0$ ls
+  MET-12.0.0  bin  compile_MET_all.sh  external_libs  install_met_env.hera  share  tar_files
 
 To confirm that MET was installed successfully, run the following command from the installation directory to check for errors in the test file:
 
 .. code-block:: ini
 		
-  grep -i error MET12.0.0/met.make_test.log
+  grep -i error MET-12.0.0/met.make_test.log
   
 If no errors are returned, the installation was successful.
 Due to the highly variable nature of hardware systems, users may encounter issues during