An analytical solution of the stationary fully-compressible linear Euler equations over orography

TL;DR

This paper derives an analytical solution for the stationary fully compressible Euler equations over orography, providing a benchmark for testing numerical weather prediction models.

Contribution

It introduces a covariant formulation-based analytical solution for stationary compressible flow over orography, validated against a spectral semi-implicit numerical model.

Findings

Numerical solutions converge to the analytical solution with increased resolution.

The analytical solution covers hydrostatic, non-hydrostatic, and potential flow regimes.

The method serves as an idealized test for numerical weather models.

Abstract

An analytical linear solution of the fully compressible Euler equations is found, in the particular case of a stationary two dimensional flow that passes over an orographic feature with small height-width ratio. A method based on the covariant formulation of the Euler equations is used, and the analytical vertical velocity as well as the horizontal velocity, density and pressure, are obtained. The analytical solution is tested against a numerical model in three different regimes, hydrostatic, non-hydrostatic and potential flow. The model used is a non-hydrostatic spectral semi-implicit model, with a height-based vertical coordinate. It is shown that there is a clear and consistent convergence of the numerical solution towards the analytical solution, when the resolution increases. The method described is intended to be used as an idealized test for numerical weather models.