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 30o 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 30o 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 500 x 500 meter spacing over the Sierra Nevada mountain range. Very weak stretching is used so that the resolution is still ~500 x 500 m over the Owen's valley. The domain extends to an altitude of 120 km and uses uniform vertical spacing of 500 m. A total of 660 x 848 x 240 mesh points are used. Sponge layers are used on all external boundaries in order to absorb outgoing waves.

Wind and Thermodynamic Profiles

Radiosonde data gathered on Febuary 17, 2016 12:00 UTC, launched from Reno, NV was used on the altitude interval (1.5 , 30) km. Wind and temperature profiles above 30 km were taken from the climatology study of Fleming et al. (1988) for February at 40o N. This is the same data that was used by Woods and Smith (2011). These wind profiles were blended together and then linearly extrapolated below 1.5 km to produce a continuous profile. 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 vorticity magnitude in the xz plane at the position y = -136 km






Animation of w' in the xz plane at the position y = -136 km






Animation of vorticity magnitude in the xz plane at a position of -50 km






Animation of w' in the xz plane at a position of -50 km






Animation of vorticity magnitude in the xy plane at an altitude of 15 km






Animation of w' in the xy plane an altitude of 15 km






Animation of vorticity magnitude in the xy plane at an altitude of 85 km






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