Coupling NWP Physics to a Three-Dimensional Spectral Element MODEL

The Navy Environmental Prediction System Using the NUMA Core (NEPTUNE) is a next generation global cloud resolving numerical weather prediction (NWP) system being developed at the Naval Research Laboratory (NRL) and the Naval Postgraduate School (NPS). The dynamical core of NEPTUNE is based upon a three-dimensional spectral element numerical representation of the continuous non-hydrostatic, deep-atmosphere Euler equations. While the spectral-element technique allows the numerical solution to be represented with an arbitrarily high order of accuracy, the irregularly spaced vertical grid points associated with the roots of the underlying basis functions complicates the coupling of physical parameterizations to dynamics. Several techniques to remap the vertical grid to a staggered, regularly spaced grid will be discussed. The remapping techniques are designed to be (i) positive definite, (ii) conservative, and (iii) invertible. Several examples using both idealized test cases and real-date global simulations will be presented. The performance of each remapping technique will be evaluated.