A non-hydrostatic semi-Lagrangian scheme on convective dynamics

A non-hydrostatic, semi-Lagrangian transport scheme is proposed. The scheme is able to solve the fully-compressible Euler equations with a minimum of filtering and approximations, allowing high-speed waves such as acoustic waves. Acoustic waves put severe limitations on the maximum time step that can be taken ensuring stability by not violating the Courant-Friedrich-Lewy criterion. Therefore, a time-split technique is incorporated such that the pressure type waves are treated with an Eulerian forward-backward method, and the advective part is treated with a semi- Lagrangian method. The scheme is able to reliably simulate convective thermals in both neutrally and stably stratified environments, including features as gravity wave oscillations and Kelvin-Helmholtz instability. A review of Eulerian and semi-Lagrangian methods is given along with a discussion of previous methods used in compressible models. Qualitative comparisons to earlier non-hydrostatic model studies are made.

Achieved the degree of M.Sc in meteorology from Niels Bohr Institute, University of Copenhagen, Denmark in 2013 with the submission of this work. Studied at Meteorologisches Institut, Freie Universität Berlin, Germany in 2011 as an integrated part of the master studies.