Sensitivity Studies on a Limited Area Mesoscale Model: An Examination of Lateral Boundary Placement, Grid Resolution and Nesting Type

摘要

With the advances of computer technology in recent years, limited area mesoscale models are being used to produce operational forecasts on a broader scale worldwide than ever before. The past limitations of computational resources have caused previous research efforts to focus more on model physics, thus creating a gap in the number of sensitivity studies conducted on these models. This research is intended to bridge a gap in the apparent paucity of sensitivity studies on the limited area model (LAM). The Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model 5 was utilized to conduct sensitivity studies on lateral boundary placement in regions of strong topography, grid resolution and nesting type. This research has resulted in three significant findings: (1) optimally placing the windward lateral boundary of a LAM with respect to the tallest peaks of a strong orography increases the model's forecast veracity; (2) the paradigm that finer grid resolutions will always produce better forecasts is flawed when there is an absence of strong ageostrophic motions in the troposphere; and (3) two-way nesting will generally produce a more accurate forecast than one-way nesting when significant ageostrophic motions are present in the troposphere.