[ferret_users] Re: HOw to convert potential temperature to in-situ temperature?

[James Orr <James.Orr@xxxxxxxxxxxx>]

Here's a response to an old unanswered question to this group:

To convert from potential temperature to in-situ temperature, it is very 
easy. It can be done simply by using the existing Ferret function that 
does the opposite.

As documented in the Ferret user manual, the function THETA_FO is designed to 
convert from in-situ temperature to potential temperature (only).  The 
arguments are

  THETA_FO( salt, temp, P, P_reference)

What is undocumented in the manual is that to do the opposite (convert in-situ 
to potential temperature), we only need to inverse the 3rd and 4th arguments. 
For example

  let Tpot     = theta_fo(35,20,5000,0)
  let Tinsitu  = theta_fo(35,19,0,5000)
  list Tpot, Tinsitu
! Results should be Tpot=19 and Tinsitu=20

This might be useful for some, e.g., ocean modelers who typically store out 
potential temperature fields but sometimes need in-situ temperature in 
post-treatments.  It would be nice if this currently undocumented feature of 
THETA_FO would be added to the user's manual.

Thanks,

Jim

-----------------------------------------------------------
Old unanswered Question from Ferret archive:
-----------------------------------------------------------
 * To: ferret_users
 * Subject: HOw to convert potential temperature to in-situ temperature?
 * From: Yang Kun
 * Date: Fri, 25 Feb 2000 15:13:43 -0600 (CST)

HI, all

I know theta_fo can calculate potential temperature.
Is there also a fuction to do the contrary thing in ferret?
Or, I have to write Fortran to do this?
Thanks.

yours,
Kun