Lorenz 84
Overview
This model was described in Lorenz (1984). [1] In Lorenz 84, DART advances the model, gets the model state and metadata describing this state, find states variables that are close to a given location, and does spatial interpolation for model state variables. The distinctive part of the model interfaces is the namelist.
The system of equations is:
and, within DART, the model parameters have default values of:
that can be altered by editing the &model_nml
namelist in the
input.nml
file.
The Lorenz 84 model has a work/workshop_setup.csh
script that compiles and runs
an example. This example is referenced specifically in Section 7 of the
DART tutorial
and is intended to provide insight into model/assimilation behavior.
The example may or may not result in good (or even decent!) results!
The Lorenz 84 model may be used instead of the Lorenz 63 model in many sections of the Tutorial. It has a more complex attractor, is not as periodic as Lorenz 63 and may be more challenging for certain filter variants.
Namelist
The &model_nml
namelist is read from the input.nml
file. Namelists
start with an ampersand &
and terminate with a slash /
. Character
strings that contain a /
must be enclosed in quotes to prevent them from
prematurely terminating the namelist.
&model_nml
a = 0.25,
b = 4.00,
f = 8.00,
g = 1.25,
deltat = 0.01,
time_step_days = 0,
time_step_seconds = 3600
/
Description of each namelist entry
Item |
Type |
Description |
---|---|---|
a |
real(r8) |
Model parameter. |
b |
real(r8) |
Model parameter. |
f |
real(r8) |
Model parameter. |
g |
real(r8) |
Model parameter. |
deltat |
real(r8) |
Non-dimensional timestep. This is mapped to the dimensional timestep specified by time_step_days and time_step_seconds. |
time_step_days |
integer |
Number of days for dimensional timestep, mapped to deltat. |
time_step_seconds |
integer |
Number of seconds for dimensional timestep, mapped to deltat. |