Prediction errors associated with sparse grid estimates of local atmospheric flows

Abstract

Numerical simulations of geophysical flows have to be done on very sparse grids. This study show that moderately stratified flows can nevertheless be predicted usefully accurate. For better grids than about  ∆x1/H~0.5 or so, recirculating domains and the characteristic wavelength of lee waves are predicted accurately while the lee wave amplitude is predicted with considerable error. The relative error of the turbulence intensity is comparable to  δ √K / √K  ~ 0.25, which is comparable to the large scale flow error and the about as accurate as any turbulence model can be. Strongly stratified flows are predicted with considerable errors even on dense grids.

Oppdragsgiver Avinor AS