A modified nonhydrostatic moist global spectral dynamical core using a dry‐mass vertical coordinate

Abstract

AbstractMost global models employ a vertical coordinate based on the moist hydrostatic pressure, and therefore do not conserve dry air mass. Such an issue should be taken seriously into account, especially in developing global high‐resolution atmospheric models to address nonhydrostatic motions explicitly. In this article, we present a modified nonhydrostatic moist global spectral dynamical core using a dry‐mass vertical coordinate, which conserves the mass of dry air naturally. In addition to the vertical coordinate, the modified dynamical core differs from the original Aladin‐NH like dynamical kernel in the state variables employed. Specifically, a new temperature variable is introduced to formulate the governing equations and the mass continuity equation is expressed in terms of the dry air density. To assess its performance, an idealized splitting supercell test is conducted. Simulation results from both the modified and original dynamical cores are presented and compared. The results indicate that only the modified dynamic core is able to simulate the splitting supercell with good accuracy comparable to reference solutions from the Model for Prediction Across Scales (MPAS).