Real-World Tests of a Tensor Stress Boundary Condition in a Regional Atmospheric Model: Mount Rainier and Mount Ngauruhoe

This study considers tests of a new tensor stress boundary condition in a regional atmospheric model, using Mount Rainier (US) and Mount Ngauruhoe (NZ) as real-world test cases. Current generation numerical weather prediction models, while capable of satisfying the kinematic boundary condition, do not adequately apply the stress condition in areas with steep and complex terrain. Modelers have attempted to avoid the situation of modeling complex surfaces by assuming the region is smoothed out and relatively flat. Using smaller slopes, the surface stress condition is applied using the flat boundary approximation, reducing the condition to three components. With improving model resolutions, however, this method is becoming increasingly inaccurate. 30-meter resolution topographic data for Mount Rainier was downloaded from the National Elevation Data page on the United States Geographic Survey's website, along with 90-meter resolution data for Mount Ngauruhoe in New Zealand from the Shuttle Radar Topography Mission's elevation data. The two examples were introduced into an idealized regional atmospheric model with the full tenor stress condition implemented. To determine the level of error in current generation models, the results are compared to simulations using the approximate flat boundary condition.