Numerical Simulations of Waves over Large Crater Topography in the Atmosphere

Abstract

umerical simulations are used to investigate waves generated by flow over crater topography of diameter 100 km in an idealized atmosphere. The atmosphere is stratified with a constant buoyancy frequency profile and the background wind is constant. This study describes the development of a low-level jet along the upstream crater slope and its interaction with the cooler air within the crater valley. This interaction results in a hydraulic jump?like structure that acts as a modified topography, forcing a beam of secondary waves. The hydraulic jump is formed by a retreating gravity current as the cool air within the crater readjusts after the initial tilting of potential temperature contours. A two-dimensional simulation is used to compare features such as wave overturning in two and three dimensions. Several variations on the atmosphere?s profile are considered, including an atmosphere with reduced constant stratification and an atmosphere that is unstratified within the crater. These results indicate that the stratification within the crater is an important component in the development of the hydraulic jump. Also, several topographic modifications are included, such as a crater with no rims and a crater with reduced diameter. These comparisons reveal that the crater rims have little impact on the general wave pattern and that the crater curvature can influence wave breaking and lateral deflections. In addition, cases with rotation break the symmetry and induce more overturning in one-half of the crater.