Downslope Windstorms. Part I: Effect of Air Density Decrease with Height

Abstract

In 1985 Smith published a solution of a nonlinear, steady-state, two-dimensional, mesoscale problem concerning airflow crossing a mountain ridge. He used his solution to explain the mechanism of severe downslope winds. In particular, Smith considered the 11 January 1972 windstorm in Boulder, when an undisturbed flow approaching the ridge embraced almost the entire thickness of the troposphere. It is known that in this case the continuity equation should allow for the fact that air density decreases with height. In the present paper we generalize Smith's solution by retaining a term in the continuity equation, which in the first approximation takes into account the decrease of air density with height. The solution obtained is analyzed in detail and compared with Smith's solution. The error of solution due to neglect of the aforementioned factor is evaluated. Some physical conclusions are drawn.