ATLAS LAr Calorimeter Commissioning for LHC Run-3

Liquid argon (LAr) sampling calorimeters are employed by ATLAS for all electromagnetic calorimetry in the pseudo-rapidity region $|\eta| < 3.2$, and for hadronic and forward calorimetry in the region from $|\eta| = 1.5$ to $|\eta| < 4.9$. After detector consolidation during a long shutdown, Run-2 started in 2015 and about \SI{150}{\per\femto\barn} of data at a center-of-mass energy of \SI{13}{\TeV} was recorded. Phase-I detector upgrades began after the end of Run-2. New trigger readout electronics of the ATLAS Liquid-Argon Calorimeter have been developed. Installation began at the start of the LHC shut down in 2019 and is expected to be completed in 2021. A commissioning campaign is underway in order to realise the capabilities of the new, higher granularity and higher precision level-1 trigger hardware in Run-3 data taking. This contribution will give an overview of the new trigger readout commissioning, as well as the preparations for Run-3 detector operation