Scientific documentation of the NCEP nonhydrostatic multiscale model on the B grid (NMMB). Part 1 Dynamics

This technical note focuses on the scientific and algorithmic approaches in the NMMB dynamics. Discussed are the NMMB dynamics solver, boundary conditions and the horizontal diffusion and other dissipative processes. The other components of the NMMB such as physical package, data assimilation, verification and the software framework are discussed elsewhere. The NMMB dynamics solver includes fast waves, advection, thermodynamic processes, a nonhydrostatic add-on module, lateral diffusion, horizontal divergence damping, coupling of the sub-grids of the semi-staggered grid B, boundary conditions, polar filtering and nesting capabilities. It also includes transport of various components of the atmosphere such as moisture variables and other tracers. This system together with various options for physics, initialization and post processing are combined within the NEMS framework to produce end-to-end multiscale simulations. The Developmental Testbed Center (DTC) and the Joint Numerical Testbed (JNT) Program in NCAR's Research Applications Laboratory supported the preparation of this Technical Note. Dr. Robert Gall is a UCAR employee who was the first National Director the DTC and formerly the Director of the JNT Program. He currently is on assignment as the Development Manager, Hurricane Forecast Improvement Program, NOAA/OST, Silver Spring, MD. Zavisa Janjic is affiliated with the Environmental Modeling Center, National Centers for Environmental Prediction, College Park, MD.