E3SMv3 is the third major E3SM release since the project’s inception a decade ago. The lower-resolution configuration, v3.LR, is the workhorse configuration consisting of a fully coupled physical model with interactive atmosphere, ocean, sea-ice, land and river components and capable of simulating thousands of years. The atmosphere grid spacing of approximately 110 km remains unchanged compared to the previous version. However, ocean and sea-ice have increased resolution in v3.LR with a quasi-uniform grid spacing of 30 km. The land and river components are now on a common ½ deg grid to facilitate feature integrations, such as water management.

We will present an overview of the changes in v3.LR compared to previous versions. They include an updated atmosphere with improved representation of variability (for example tropical wave activity, diurnal cycle of precipitation). The land model now incorporates interactive vegetation that responds climate forcings and an improved representation of radiation over complex terrain. The column physics in the sea-ice has been updated to the latest version of Icepack and numerous other improvements have also been incorporated. The ocean incorporates a new more efficient time-stepping algorithm, as well as new sub-mesoscale parameterizations.

In addition, significant efforts were dedicated on the representation of aerosols in the atmosphere to reduce the excessive forcing in previous versions. With a smaller magnitude aerosol forcing, E3SMv3.LR can now realistically simulate the evolution of the surface temperature over the historical period. The evolution of global ocean heat content is also greatly improved as a result.