Sierra Nevada/Owens Valley Simulation

This page describes a numerical Simulation of waves over the Owen's Valley generated by winds over the Sierra Nevada Mountain Range.

Computational Domain

The layout of the of the simulation is shown in the figure below. Note that the computational domain (thin white line) is rotated at 300 with respect to lines of constant latitude.

domain

Just the computational domain is shown in the figure below. In this plot, and those that follow the results are shown in the computational frame, which is rotated 300 with respect to earth longitude/latitude coordinates. The terrain is damped around the domain edges in order to achieve a fixed elevation around the perimeter.

surface

The mesh is clustered in both horizontal directions in order to achieve 1000 x 1000 meter spacing over the Sierra Nevada mountain range. Very weak stretching is used so that the resolution is still ~1000x1000 m over the Owen's valley. The domain extends to an altitude of 96 km and uses a uniform vertical spacing of 1000 m. A total of 200 x 440 x 96 mesh points are used. Sponge layers are used on all external boundaries in order to absorb outgoing waves.

Wind and Thermodynamic Profiles

Wind and temperature profiles were taken from the climatology study of Fleming et al. (1988) for February at 400 N. This is the same data that was used by Woods and Smith (2011). The climatology does not provide profiles of meridional wind so that component was simply set to zero. Plots of the various profiles are shown below.

winds

magnitude

direction

direction

temperature

N_sq

N_sq

Mean wind evolution

Here the winds are initially set to zero from the surface to an altitude of about 20 km. At this point the wind transitions to the profiles shown in the plots above. Forcing terms then gradually introduce winds near the surface with the objective of achieving the profile shown above 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 45 minutes.

Animation of u' in the xz plane at the position of maximum mountain height






Animation of u' in the xy plane at an altitude of 85 km






Animation of w' in the xy plane at an altitude of 85 km