A Nested Grid, Nonhydrostatic, Elastic Model Using a Terrain-following Coordinate Transformation: The Radiative-nesting Boundary Conditions

Abstract

A nested grid, nonhydrostatic, elastic model using a terrain-following coordinate transformation is presented with a unique application of grid-nesting techniques to the time-splitting elastic model. To minimize the wave reflection along the lateral and the upper boundaries of the nested fine-grid model, the conventional nested-grid scheme has been modified so that the fine-grid model has its own “independent” radiative boundary conditions as well as “dependent” nested boundary conditions. This modification is crucial to the success of nested grid simulations. A simulation of the 10-m-high Witch of Agnesi Mountain provides the control to test this new model. The results show that the model produces the same solution as that derived from a simple linear analytic model. The model used in the control case is then double-nested by a fine-grid model that has its primary domain zoomed into the area around the mountain. Using this configuration, one-way and two-way grid-nesting sensitivity experiments with various boundary conditions are performed. In order to examine the robustness of the newly developed nesting scheme, the model is further tested by conducting the triple-nesting case, the high-mountain case, and the downslope windstorm case.