Rocky Mountain Simulation

This page describes a numerical simulation of gravity waves over the Rocky Mountains in Colorado.

Computational Domain

The layout of the of the simulation is shown in the figure below. Note that the computational domain is rotated at 7o with respect to lines of constant latitude.

surface

The mesh is clustered in both horizontal directions in order to achieve 250 x 250 meter spacing over the mountain range in the region shown by the black rectangle. Weak stretching of ~1.5% is used to the edges. The domain extends to an altitude of 40 km and uses uniform vertical spacing of 250 m. A total of 768 x 520 x 160 mesh points are used. Characteristic boundary conditions are used on all sides except the surface.

Wind and Thermodynamic Profiles

The mean winds and temperature profile are taken from radiosonde data on February 19th, 2016, from launch site in Grand Junction. These profiles extend to an altitude of 31 km. A third order interpolating polynomial is then used to smoothly extend the winds above this altitude using the condition that U=V=0 at the upper boundary. Plots of various profiles for the balloon measurements are shown below.

winds

winds

winds

winds

winds

winds

Wind Condition


The mean winds near the surface are increased in time. Forcing terms gradually introduce winds near the surface with the objective of achieving the wind profile within a two hour period. A hyperbolic tangent function is used in order to produce gentle acceleration of the wind near the beginning and end of the forcing period. The maximum forcing rate is equivalent to that of a linear ramp with a duration of thirty minutes.

Results

Animation of w' in the xz plane at the position y = 0




Animation of w' in the xy plane at altitude of 20 km




Frames of w' in the xy plane at altitude of 25 km




Frames of w' in the xy plane at altitude of 30 km




Frames of w' in the xy plane at altitude of 35 km