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.