diff --git a/cmake/ctest/drivers/atdm/ats2/local-driver.sh b/cmake/ctest/drivers/atdm/ats2/local-driver.sh
index 8f12bd099d07..eaeab9c33132 100755
--- a/cmake/ctest/drivers/atdm/ats2/local-driver.sh
+++ b/cmake/ctest/drivers/atdm/ats2/local-driver.sh
@@ -16,6 +16,9 @@ source $WORKSPACE/Trilinos/cmake/std/atdm/load-env.sh $JOB_NAME
 
 set -x
 
+# Allow default setting for TPETRA_ASSUME_CUDA_AWARE_MPI=0 in trilinos_jsrun
+unset TPETRA_ASSUME_CUDA_AWARE_MPI
+
 atdm_run_script_on_compute_node \
   $WORKSPACE/Trilinos/cmake/ctest/drivers/atdm/ctest-s-driver.sh \
   $PWD/ctest-s-driver.out \
diff --git a/cmake/std/atdm/README.md b/cmake/std/atdm/README.md
index 61c1808590e3..e3cdc553edb1 100644
--- a/cmake/std/atdm/README.md
+++ b/cmake/std/atdm/README.md
@@ -1037,12 +1037,12 @@ $ bsub -x -Is -n 20 \
 
 ### ATS-2
 
-Once logged on a suppported ATS-2 system like 'vortex' (SRN), one can either
-build and configure on the login node or the compute node. Make sure to setup
-SSH keys as described in `/opt/VORTEX_INTRO` before trying to build on a
-compute node. For example to configure, build and run the tests for the
-default `cuda-debug` build for `Kokkos` (after cloning Trilinos on the
-`develop` branch), do:
+Once logged on a supported ATS-2 system like 'vortex' (SRN), one can either
+build and configure on a login node or a compute node.  Make sure to setup SSH
+keys as described in `/opt/VORTEX_INTRO` before trying to build on a compute
+node.  For example, to configure, build and run the tests for the default
+`cuda-debug` build for `Kokkos` (after cloning Trilinos on the `develop`
+branch), do:
 
 ```bash
 $ cd <some_build_dir>/
@@ -1058,7 +1058,8 @@ $ cmake -GNinja \
 $ make NP=20
 ```
 
-You may run the above commands from an interactive bsub session as well:
+You may run the above commands from an interactive bsub session as well using:
+
 ```bash
 $ bsub -J <YOUR_JOB_NAME> -W 4:00 -Is bash
 ```
@@ -1067,10 +1068,36 @@ CTest runs everything using the `jsrun` command. You must run jsrun from a
 compute node which can be acquired using the above bsub command.
 
 Once you're on a compute node, you can run ctest. For example:
+
 ```bash
 $ ctest -j4
 ```
 
+The MPI test exectuables are run by a wrapper script `trilinos_jsrun` which
+calls the `jsrun` command which modifies the input arguments to accommodate
+the MPI test suite in Trilinos (see the implementation of the script
+`trilinos_jsrun` for details).  By default, the script `trilinos_jsrun` will
+set `export TPETRA_ASSUME_CUDA_AWARE_MPI=0` if `TPETRA_ASSUME_CUDA_AWARE_MPI`
+is unset in the environment.  Therefore, by default, the tests are run without
+CUDA-aware MPI on this system.
+
+To explicitly **disable CUDA-aware MPI** when running the test suite, set the
+environment variable:
+
+```bash
+$ export TPETRA_ASSUME_CUDA_AWARE_MPI=0
+$ ctest -j4
+```
+
+and to explicitly **enable CUDA-aware MPI** when running the test suite set:
+
+```bash
+$ export TPETRA_ASSUME_CUDA_AWARE_MPI=1
+$ ctest -j4
+```
+
+before running `ctest`.
+
 **NOTES:**
 - Do NOT do `module purge` before loading the environment. Simply start off with
   a clean default environment on vortex.
diff --git a/cmake/std/atdm/ats2/environment.sh b/cmake/std/atdm/ats2/environment.sh
index bfd8b093d1d1..539277be4546 100644
--- a/cmake/std/atdm/ats2/environment.sh
+++ b/cmake/std/atdm/ats2/environment.sh
@@ -186,8 +186,6 @@ if [[ "$ATDM_CONFIG_COMPILER" == "CUDA-10.1.243_"* ]]; then
   export KOKKOS_NUM_DEVICES=4
 
   # CTEST Settings
-  # TPETRA_ASSUME_CUDA_AWARE_MPI is used by cmake/std/atdm/ats2/trilinos_jsrun
-  export TPETRA_ASSUME_CUDA_AWARE_MPI=0
   # Trilinos_CTEST_RUN_CUDA_AWARE_MPI is used by cmake/ctest/driver/atdm/ats2/local-driver.sh
   export Trilinos_CTEST_RUN_CUDA_AWARE_MPI=1
 
diff --git a/cmake/std/atdm/ats2/trilinos_jsrun b/cmake/std/atdm/ats2/trilinos_jsrun
index 7b952e7cbfbb..c6289bc4c22a 100755
--- a/cmake/std/atdm/ats2/trilinos_jsrun
+++ b/cmake/std/atdm/ats2/trilinos_jsrun
@@ -72,7 +72,7 @@ function evaluate_jsrun_command {
 # Check if TPETRA_ASSUME_CUDA_AWARE_MPI is set and default to 0 if unset.
 if [[ "$TPETRA_ASSUME_CUDA_AWARE_MPI" != "0" ]] && [[ "$TPETRA_ASSUME_CUDA_AWARE_MPI" != "1" ]]; then
   echo "WARNING, you have not set TPETRA_ASSUME_CUDA_AWARE_MPI=0 or 1, defaulting to TPETRA_ASSUME_CUDA_AWARE_MPI=0"
-  export TPETRA_ASSUME_CUDA_AWARE=0
+  export TPETRA_ASSUME_CUDA_AWARE_MPI=0
 fi
 
 # Parse input arguments and modify them for jsrun
diff --git a/cmake/std/atdm/utils/unset_atdm_config_vars_environment.sh b/cmake/std/atdm/utils/unset_atdm_config_vars_environment.sh
index 4312ded823f8..2fefbf12f49a 100644
--- a/cmake/std/atdm/utils/unset_atdm_config_vars_environment.sh
+++ b/cmake/std/atdm/utils/unset_atdm_config_vars_environment.sh
@@ -9,7 +9,6 @@ unset OMP_PLACES
 unset OMPI_CC
 unset OMPI_CXX
 unset OMPI_FC
-unset TPETRA_ASSUME_CUDA_AWARE_MPI
 unset Trilinos_CTEST_RUN_CUDA_AWARE_MPI
 unset ATDM_CONFIG_ENABLE_SPARC_SETTINGS
 unset ATDM_CONFIG_USE_NINJA