Harmonie-Arome on AWS

Cloud computing provides on-demand availability of all computer system resources and is, consequently, of  
general interest to National Meteorological and Hydrological Services. However, how does one get started and is true HPC a real option in the cloud?"
In connection with the work on a forecast benchmark for United Weather Centre-West project and the
upgrade of the operational forecast system at the Danish Meteorological Institute (DMI), both of
which are based on the Harmonie-arome 43h2.1 released by the Hirlam-C consortium, we ported and
tested the Harmonie forecast system on the Amazon Web Services (AWS), a public cloud. In these explorations, we
tested both a stand-alone benchmark configuration and a full system configuration. The latter includes
boundary preparation and observation pre-processing, data assimilation and forecast cycling, and the
subsequent postprocessing; i.e. execution of a full NWP cycling dataflow with the required typical
suite of applications using the Harmonie scripting system.
We will share our experiences of porting the Harmonie-Arome weather forecasting system to AWS.There are both differences and the similarities between running
NWP on-premise versus running it on AWS and we will first focus on describing these. Then we will cross-compare
the performance obtained on the on-premise systems versus the ones obtained on AWS. Finally we will describe
our approach to integrate the on-premise clusters with AWS clusters. The approach will be using layered builds
of AMIs (Amazon Machine Images). Moreover, these builds will be launched in a fully automatic fashion using Git
CI/CD pipelines. This approach has the potential to have 24/7 NWP production systems running on our on-premise clusters that
will have AWS sitting in the back 24/7 both as a fallback option and as a bursting option to our on-premise
production.