Re: [ferret_users] Stream function

[Jian Ma <jianma@xxxxxxxxxx>]

Hi William,

Thanks. But the meteorologist normally do it on global horizontal
fields. That way you are easier to solve the Poisson equation to get
both stream function and velocity potential. However, for walker
circulation, it is a integration within limited latitudes with up and
surface boundaries and continuous longitudinal boundary condition. It
seems hard for me to get the solution. The P coordinate also increases
the complexity of doing vorticity calculation. I guess the divergence is
OK so I plan to solve the divergent wind first and then subtract it from
the total to get rotational wind. But still I need to solve the Poisson
equation with boundary conditions.

Many thanks,
Tony

On Wed, 2010-01-20 at 19:04 -0800, William S. Kessler wrote:
> Yes, you are right. This script does not distinguish the divergent  
> and nondivergent part of a circulation. It assumes that the input is  
> already nondivergent.
> 
> In fact, I don't know how to make this separation! In oceanography we  
> typically do this by integrating vertically top-to-bottom or coast-to- 
> coast, which ensures nondivergence.
> 
> So I'm really not sure how to answer your question, but I know that  
> meteorologists routinely do this separation, so you should be able to  
> find out.
> 
> Good luck, and when you find out and write the script, please post it  
> to the group!
> 
> Billy K
> 
> On 20 Jan 10, at 6:49 PM, Jian Ma wrote:
> 
> > Hi Billy,
> >
> > Thanks. I think you are talking about this:
> > http://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2002/ 
> > msg00155.html
> >
> > But I think this simple integration can only be applied on wind fields
> > that is non-divergent. Will it be suitable for Walker circulation?
> >
> > Tony
> >
> > On Wed, 2010-01-20 at 17:28 -0800, William S. Kessler wrote:
> >> I think you can search the user group archives for "streamfunction".
> >> I wrote a script to do this a long time ago and posted it to the
> >> group. Billy K
> >>
> >> On 20 Jan 10, at 4:01 PM, Jian Ma wrote:
> >>
> >>> Hi All,
> >>>
> >>> Maybe this is not a question very related to Ferret. Is there any  
> >>> good
> >>> method to plot the stream function of the non-divergent component
> >>> of any
> >>> flow field? Specifically, I want to plot the Walker circulation. The
> >>> Hadley cell seems easier since it is non-divergent when zonally
> >>> integrated.
> >>>
> >>> Many thanks,
> >>> Tony
> >>>
> >>
> >
>