Summary
We have used a two dimensional version of a nonhydrostatic mesoscale model to simulate atmospheric gravity currents for different thermal stratification. The horizontal and vertical grid increments are chosen such, that the major features of a current like head and elevated nose are resolvable.
When the density current propagates into a neutral stratified environment it was found, that frontspeed agrees well with an empirical formula. Also characteristic length scales like depth of the head or height of the following cold air body agree well with observations found in water tank experiments.
When a stable atmosphere is adopted, the front moves faster and the generated gravity waves have a significant influence on the atmospheric variables ahead of the current. This results especially in a pressure increase before the front arrives, an effect, which was found in observations, too.
Finally, it is shown, that an elevated inversion, embedded in a stable layer, intensifies the vertical velocities and therefore the mesoscale heat flux, which results in a stronger entrainment. For this case a remarkable decrease of front speed is simulated with time.
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Bischoff-Gauss, I., Gross, G. Numerical studies on cold fronts Part I: Gravity flows in a neutral and stratified atmosphere. Meteorl. Atmos. Phys. 40, 150–158 (1989). https://doi.org/10.1007/BF01032455
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DOI: https://doi.org/10.1007/BF01032455