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[IDV #HVX-641068]: 20130530: need simple example of back trajectories in IDV

> >
> > Hi Guys,
> >
> > Can you give me a quick ABC on how to do back trajectories in the
> > IDV?
> >
> > One group of students here at the PASI will be working on transport
> > of Saharan dust to the Caribbean, and it would be very useful to
> > be able to illustrate the likely origins of air parcels sampled.
> >
> > This will be used Friday afternoon in a computer lab.
> >
> > Thanks in advance...
> >
> > Cheers,
> >
> > Tom
> 
> Tom,
> It is very easy to do.
> 1)Open a globe view window.
> 
> 2)Load a dataset, gfs 1 degree, you may need more than one dataset since it 
> takes pretty long time to move dust from Saharan to Caribbean, if so, 
> aggregate them.
> 
> 3)In the field Selector,  select momentum > derived > Grid 3D trajectory, 
> click create display, when a window popup, select the colored by parameter. 
> Note: it would be good to use property window to subset the time, use every 
> other, or something, otherwise, it is too big to load every time step.
> 
> 4)In the trajectory control, select level to 85000, inital area as 
> "Rectangle",  and check the "Backward trajectory" box,  and draw a rectangle 
> in the globe view window around the Caribbean region, and click "Create 
> Trajectory"
> 
> The only thing I worry about is the internet speed if you are getting data 
> from remote server.
> 
> 

After the trajectory display created:

1)In the control, select Times tab, and change the time mode to: Start time as 
Relative to End Time, offset to -6 hour, and End time:  from Animation Time.


2) You can use the animation widget to run the animation backward.

3) Note: you need to aggregate 2 gfs data to cover the period of movement, but 
there should be no time overlapped. 

have fun!

Yuan
> Yuan
> 
> > --
> > +----------------------------------------------------------------------------+
> > * Tom Yoksas                                            UCAR Unidata 
> > Program *
> > * (303) 497-8642 (last resort)                                 P.O. Box 
> > 3000 *
> > * address@hidden                                  Boulder, CO 80307 *
> > * Unidata WWW Service                           
> > http://www.unidata.ucar.edu/ *
> > +----------------------------------------------------------------------------+
> >
> >
> 


Ticket Details
===================
Ticket ID: HVX-641068
Department: Support IDV
Priority: Normal
Status: Closed