diff --git a/definition-files/almalinux/Singularity.base b/definition-files/almalinux/Singularity.base
index 03700390c5dc004a51bef72ff1a98a04c97265da..ddcf79da1d781d1eaa826411bceead54ceda960d 100644
--- a/definition-files/almalinux/Singularity.base
+++ b/definition-files/almalinux/Singularity.base
@@ -18,6 +18,7 @@ From: almalinux:8
echo "linux $(cat /etc/os-release | grep PRETTY_NAME | cut -d'=' -f2)" >> "$SINGULARITY_LABELS"
%environment
+ export LC_ALL=C
export LANG=C.UTF-8
export LIBRARY=/usr/lib64:/lib64:/lib
export INCLUDE=/usr/include
\ No newline at end of file
diff --git a/definition-files/almalinux/Singularity.imagemagick b/definition-files/almalinux/Singularity.imagemagick
index e47c7c92e0a63ea57a18b2c53022d85cafc9894c..8b3744ee562388e25d28237ee544f377cb934f4e 100644
--- a/definition-files/almalinux/Singularity.imagemagick
+++ b/definition-files/almalinux/Singularity.imagemagick
@@ -27,6 +27,7 @@ From: almalinux:8
echo "linux $(cat /etc/os-release | grep PRETTY_NAME | cut -d'=' -f2)" >> "$SINGULARITY_LABELS"
%environment
+ export LC_ALL=C
export LANG=C.UTF-8
export LIBRARY=/usr/lib64:/lib64:/lib
export INCLUDE=/usr/include
\ No newline at end of file
diff --git a/definition-files/almalinux/Singularity.met b/definition-files/almalinux/Singularity.met
index 86dbcbe10fc43ee073e72220d439e07d5f2307e1..53e21f17a785d91feaf4d9552168d138ce93c7db 100644
--- a/definition-files/almalinux/Singularity.met
+++ b/definition-files/almalinux/Singularity.met
@@ -53,6 +53,8 @@ From: almalinux:8
echo "linux $(cat /etc/os-release | grep PRETTY_NAME | cut -d'=' -f2)" >> "$SINGULARITY_LABELS"
%environment
+ export LC_ALL=C
+ export LANG=C.UTF-8
export LIBRARY=/usr/lib64:/lib64:/lib
export INCLUDE=/usr/lib64/gfortran/modules:/usr/include
diff --git a/definition-files/almalinux/Singularity.met.ompi b/definition-files/almalinux/Singularity.met.ompi
index c5c1d6122926ea87db5082d8fbb436b4bfc2dcfc..e5fa89576cef92d5aa77b014447d518fde0338a4 100644
--- a/definition-files/almalinux/Singularity.met.ompi
+++ b/definition-files/almalinux/Singularity.met.ompi
@@ -48,6 +48,8 @@ From: almalinux:8
echo "linux $(cat /etc/os-release | grep PRETTY_NAME | cut -d'=' -f2)" >> "$SINGULARITY_LABELS"
%environment
+ export LC_ALL=C
+ export LANG=C.UTF-8
# need to add openmpi to PATH
export PATH=/usr/lib64/openmpi/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
export LIBRARY=/usr/lib64/openmpi/lib:/usr/lib64:/lib64:/lib
diff --git a/definition-files/almalinux/Singularity.spack b/definition-files/almalinux/Singularity.spack
index bc2ff4421095789e7305629c855fda48a3fe15f0..b2494aee20b7c72c0bf0b9ca47540141387b9ccb 100644
--- a/definition-files/almalinux/Singularity.spack
+++ b/definition-files/almalinux/Singularity.spack
@@ -69,6 +69,8 @@ From: almalinux:8
spack gc -y
%environment
+ export LC_ALL=C
+ export LANG=C.UTF-8
export SPACK_ROOT=/opt/spack
export DEBIAN_FRONTEND=noninteractive
diff --git a/definition-files/ubuntu/Singularity.18.04.base b/definition-files/ubuntu/Singularity.18.04.base
index 0080fccd018317a5c4452ca91df0993b1c7350fe..6aa685d9c3b24e9474bf8318af92dcf99681ac12 100644
--- a/definition-files/ubuntu/Singularity.18.04.base
+++ b/definition-files/ubuntu/Singularity.18.04.base
@@ -18,6 +18,7 @@ From: ubuntu:18.04
echo "linux $(cat /etc/os-release | grep PRETTY_NAME | cut -d'=' -f2)" >> "$SINGULARITY_LABELS"
%environment
+ export LC_ALL=C
export LANG=C.UTF-8
export LIBRARY=/usr/lib64:/lib64:/lib
export INCLUDE=/usr/include
\ No newline at end of file
diff --git a/models/ICON/Singularity.gcc b/models/ICON/Singularity.gcc
new file mode 100644
index 0000000000000000000000000000000000000000..a5e78c821ad5ed3f251a87ab2912b2cb879707da
--- /dev/null
+++ b/models/ICON/Singularity.gcc
@@ -0,0 +1,55 @@
+Bootstrap: docker
+From: ubuntu:20.04
+
+%labels
+ maintainer IT-IMGW <it.img-wien@univie.ac.at>
+
+%post
+# set noninteractive installation
+export DEBIAN_FRONTEND=noninteractive
+# Install building tools and ICON dependencies:
+apt update -y \
+&& apt install -y \
+ build-essential \
+ python3 \
+ gcc \
+ gfortran \
+ libopenmpi-dev \
+ libhdf5-dev \
+ libnetcdf-dev \
+ libnetcdff-dev \
+ libeccodes-dev \
+ libblas-dev \
+ liblapack-dev \
+ libxml2-dev
+
+
+# Select the compiler:
+#update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-6 50 \
+# --slave /usr/bin/gfortran gfortran /usr/bin/gfortran-6
+
+# The command above can be reverted as follows:
+# sudo update-alternatives --remove gcc /usr/bin/gcc-6
+
+# Select MPI libraries and compiler wrappers
+# update-alternatives --set mpi /usr/include/mpich
+# update-alternatives --set mpirun /usr/bin/mpirun.mpich
+# update-alternatives --set mpi /usr/lib/x86_64-linux-gnu/openmpi/include
+# update-alternatives --set mpirun /usr/bin/mpirun.openmpi
+
+# If the two non-interactive commands above do not work,
+# try the interactive analogues:
+# sudo update-alternatives --config mpirun
+# sudo update-alternatives --config mpi
+
+# Install optional tools:
+apt install -y ksh cdo
+
+# set timezone manually
+ln -fs /usr/share/zoneinfo/UTC /etc/localtime
+dpkg-reconfigure --frontend noninteractive tzdata
+
+%environment
+ # What do we need to build ICON?
+ export INCLUDE=/usr/include/x86_64-linux-gnu
+ export LIBRARY=/usr/lib/x86_64-linux-gnu
diff --git a/models/ICON/Singularity.gcc6 b/models/ICON/Singularity.gcc6
deleted file mode 100644
index 99d6eb46d66cc2f511cf141304af4d21ba882929..0000000000000000000000000000000000000000
--- a/models/ICON/Singularity.gcc6
+++ /dev/null
@@ -1,44 +0,0 @@
-Bootstrap: docker
-From: ubuntu:18.04
-
-%labels
- maintainer IT-IMGW <it.img-wien@univie.ac.at>
-
-%post
-# Install building tools and ICON dependencies:
-apt install -y \
- build-essential \
- python3 \
- gcc-6 \
- gfortran-6 \
- libopenmpi-dev \
- libmpich-dev \
- libhdf5-dev \
- libnetcdf-dev \
- libnetcdff-dev \
- libeccodes-dev \
- libblas-dev \
- liblapack-dev \
- libxml2-dev
-
-# Select the compiler:
-update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-6 50 \
- --slave /usr/bin/gfortran gfortran /usr/bin/gfortran-6
-
-# The command above can be reverted as follows:
-# sudo update-alternatives --remove gcc /usr/bin/gcc-6
-
-# Select MPI libraries and compiler wrappers
-update-alternatives --set mpi /usr/include/mpich
-update-alternatives --set mpirun /usr/bin/mpirun.mpich
-
-# If the two non-interactive commands above do not work,
-# try the interactive analogues:
-# sudo update-alternatives --config mpirun
-# sudo update-alternatives --config mpi
-
-# Install optional tools:
-apt install -y ksh cdo
-
-%environment
-#What do we need to build ICON?
\ No newline at end of file