Annuals of the Disaster Prevention Research Institute, 46 B, 337-346
Accuracy of terrain following coordinates over isolated mountain: Steep mountain model intercomparison project (St-MIP).
By
Satomura, T., T. Iwasaki, K. Saito, C. Muroi and K. Tsuboki
Abstract
Following the recent rapid increase of computational power, resolutions of atmospheric
numerical models increase and steep slopes are resolved in models in mountainous areas.To
examine the accuracy of the
z*
coordinates, which is one of the most common coordinates
over complex terrain for atmospheric models and to study the ability of representation of
flows over steep slope, a Steep Mountain Model Intercomparison Project (St-MIP) was
completed with three nonhydrostatic atmospheric models. Mountain waves over bell-shaped
mountains with various half-widths and heights ranging from 0.6 to more than 45 degrees of
averaged inclination angles were compared with theoretical calculations and also among
models. It is shown that models using the
z*
coordinates simulates waves unexpectedly well
over very steep mountains provided that the horizontal grid size is small enough to represent
the mountain shape smoothly. However, only a model which uses implicit method both in the
horizontal and vertical direction cannot complete the time integration.