Andes Simulation Resolution Study
This page describes a set of numerical simulations at progressively coarser
resolution to compare with the
Andes07 results, which
use 500 m isotropic mesh spacing. Four new simulations were conducted, having
horizontal resolutions of 1000, 2000, 4000 and 8000 m. The same vertical
mesh was used for all three simulations and it has 500 m spacing at the
surface,stretching to 1000 m spacing at an altitude of 40 km and then uniform
spacing at 1000 m to the top of the domain. The intent here is to mimic
mesoscale simulations, which are typically able to have higher resolution in
the vertical direction as opposed to the horizontal. This analysis is
focused on x-z views over the Southern Massif, and x-y views at 70 km altitude.
An extention of this study using identical vertical meshes can be found here Andes_Vertical_Mesh
Mesh Comparison
Horizontal Spacings
Each computational grid uses the same strategy as in Andes07 with uniform high
resolution used over the Andes and then progressively coarser mesh in the
horizontal directions when moving towards the lateral boundaries. The white
lines in the image below show the region of uniform spacing and this is
identical to what was used in the Andes07 simulation. The only difference is
that the horizontal spacings in the high-resolution zone is increased from 500
m in the Andes07 simulation to 1000, 2000, 4000, and 8000 m here. The dotted
white line in the image below indicates the location of the x-z views shown
below.
Vertical Spacing
Each computational domain extends to an altitude of 201 km and uses 500 m
resolution at the surface followed by stretching to 1000 m at an altitude
of 40 km. The vertical mesh is then uniform at 1000 m above 40 km.
NOTE: The reference simulation Andes07 uses a vertical mesh spacing of 500 m to an altitude of 144 km and then very gentle stretching to the top of the domain (200 km).
Stretching
The the rate at which the mesh is stretched in all three directions is
approximately equal ~1.6%, which is nearly identical to what was used in
the Andes07 run.
Wind and Thermodynamic Profiles
Forcing
Forcing terms gradually introduce winds near the surface with the
objective of achieving the wind profile within a twelve 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 four hours.
The wind profile and forcing strategy are idetical to what was done in the Andes07 run.
The wind profile and forcing strategy are idetical to what was done in the Andes07 run.
