MPAS Version 5.1

This minor release of MPAS introduces fixes for several issues in the MPAS v5.0 major release of the atmosphere core, including:

• Re-engineering of the 3-d divergence damping mechanism to improve model stability in some variable-resolution simulations
• Making the upper gravity-wave absorbing layer scale aware, which is necessary to effectively damp vertically propagating waves in the coarse part of variable-resolution meshes
• A fix for patches of high 2-m theta sometimes found in simulations with the MYNN surface layer scheme (part of the 'convection_permitting' suite)
• A new initialization option to extrapolate temperature below the first-guess surface with a lapse rate, needed for usable initialization in some cases
• A fix for an issue in which writing 'mslp', but not an isobaric temperature field, to an output stream lead to garbage for MSLP field
• Changes to fix compilation issues on macOS case-insensitive filesystems with GEN_F90=true
• Changes to properly handle the ECMWF 100-289 cm soil layer
• A fix for initializing with hybrid-level first-guess data that provides a 3-d 'PRESSURE' field
• A fix for compiling on BlueGene systems
• Fixes for various memory issues, mostly related to the expanded use of 'packages' in the v5.0 release

Note that namelist files used with MPAS v5.0 must be modified before they can be used with MPAS v5.1. Specifically, the 'config_smdiv_p_forward' namelist option has been removed, and the default value for 'config_smdiv' has been changed to 0.1.