Abstract

Moves to increasingly high-resolution models give rise to more variations in the underlying orography being captured by the model grid. Consequently, high-resolution models must overcome instabilities associated with terrain-following approaches. This work further explores the capabilities of a cut-cell representation of orography for idealised orographically-forced and moist microscale flows. The model is based on terrain-intersecting coordinates and solves flow in the resulting cut-cells using a finite-volume approximation. The model has been designed for the purposes of very high-resolution simulations. Comparisons with benchmark orographic and moist test cases demonstrate very good results. Further tests show the potential for the cut-cell approach for stably resolving flows over very steep orography.