Verification of a Modified Nonhydrostatic Global Spectral Dynamical Core Based on the Dry-Mass Vertical Coordinate: Three-Dimensional Idealized Test Cases

The newly developed nonhydrostatic (NH) global spectral dynamical core is evaluated by using three-dimensional (3D) benchmark tests with/without moisture. This new dynamical core differs from the original Aladin-NH like one in the combined use of a dry-mass vertical coordinate and a new temperature variable, and thus, it inherently conserves the dry air mass and includes the mass sink effect associated with precipitation flux. Some 3D dry benchmark tests are first conducted, including steady state, dry baroclinic waves, mountain waves in non-sheared and sheared background flows, and a dry Held-Suarez test. The results from these test cases demonstrate that the present dynamical core is accurate and robust in applications on the sphere, especially for addressing the nonhydrostatic effects. Then, three additional moist test cases are conducted to further explore the improvement of the new dynamical core. Importantly, in contrast to the original Aladin-NH like one, the new dynamical core prefers to obtain simulated tropical cyclone with lower pressure, stronger wind speeds, and faster northward movement, which is much closer to the results from the Model for Prediction Across Scales (MPAS), and it also enhances the updrafts and provides enhanced precipitation rate in the tropics, which partially compensates the inefficient vertical transport due to the absence of the deep convection parameterization in the moist Held-Suarez test, thus demonstrating its potential value for full-physics global NH numerical weather prediction application.