The Simple Cloud Resolving E3SM Atmosphere Model (SCREAM) is a new global atmosphere model designed for 3 km horizontal grid spacing. Obtaining reasonable simulation speed at this resolution requires use of graphical processing units (GPUs). SCREAM is written in C++ using the Kokkos library to achieve performance both on GPUs and on conventional computer architectures. By keeping the SCREAM code base simple, implementation of SCREAM version 1 was achieved by a relatively small team in less than 4 years. Minimizing complexity also has the benefit of making results easier to understand and therefore trust. Another pillar of the SCREAM project is exhaustive unit testing, which has helped avoid bugs. To guide C++ implementation and provide early science results, a prototype of SCREAM was created by extending the existing F90 E3SM atmosphere model. In this presentation, we will provide lessons learned from SCREAM development and analysis of existing SCREAM simulations, which shows that increased resolution fixes many but not all biases in the standard E3SM model.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-825049.