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Initialising em_tropical_cyclone for the southern hemisphere


New member
I am attempting to run an idealised tropical cyclone simulation for the southern hemisphere, however I am running into some trouble when initialising the vortex.

In order to change the starting conditions, I am modifying 'module_initialize_tropical_cyclone.F' (user settings shown below).

Flipping the sign of the Coriolis parameter results in the intended Coriolis force for the southern hemisphere, however the actual winds of the initial vortex remain spinning counter-clockwise:


! Parameters for analytic vortex:
! Reference: Rotunno and Emanuel, 1987, JAS, p. 549

r0 = 600000.0 ! outer radius (m)
rmax = 135000.0 ! approximate radius of max winds (m)
vmax = 15.0 ! approximate value of max wind speed (m/s)
zdd = 20000.0 ! depth of vortex (m)

! other settings:

fcor = -5.0e-5 ! Coriolis parameter (1/s)
sst = 30.0 ! sea-surface temperature (Celsius)


For context, below is an ncview visualisation of horizontal-axis winds using the above settings:

Unfortunately, flipping the sign of vmax seemingly has no effect, with the vortex appearing identical to the image above.

Flipping the signs of r0 and rmax results in the complete absence of a vortex.

What actions can I take to create the desired simulation? Is there something here I have missed?
Last edited:
I would like to apologize for the long delay in response. Can you let me know if you are still experiencing this issue? Thanks!
Have you also tried changing the center lat/lon so that the domain is located in the southern hemisphere? Near the top of module_initialize_tropical_cyclone.F, these are the default settings:

  CALL nl_set_cen_lat(1,20.)
  CALL nl_set_cen_lon(1,-105.)

What happens if you change those, as well?

Just to note: I'm sure you are, but make sure you are recompiling the code each time you make a change to the module_* file. Because you aren't modifying anything with the registry, you don't need to clean or reconfigure the code each time. Just simply recompile.