[IDV #GES-343526]: Isosurfaces

Hi Jerry-

> Full Name: Jerry Blechman
> Email Address: address@hidden
> Organization: SUNY-Oneonta
> Package Version: 2.5 build date:2008-05-08 07:05 UTC
> Operating System: Windows XP
> Hardware: Java: home: C:\Program Files\IDV_2.5\jre version: 1.5.0_11 
> j3d:1.3.2 fcs (build12)
> Description of problem: I'm trying to learn the IDV.  I've been to an IDV 
> workshop and now I've loaded it onto the computers in our lab.

Glad to hear you are going further with this.
 
> I requested a 3D isosurface of the geopotential height at 700 hPa.  It came 
> out as a flat surface (see attachments).

An isosurface of geopotential height will be a flat surface since the
vertical dimension in the IDV box is height.  Therefore, when you select
3000 gpm, you are getting a plot of everywhere the height is 3000
gpm, which will be the same point above the bottom of the box.  However,
the pressure at each point might be different.

> I set the value at 3000 gpm but if the surface is 700 hPa, that should look 
> low in Canada around Hudson Bay and high near the Carolinas.
> It looks like it's plotting the 3000 gpm surface at 3000 gpm.
> 
> How do i get the three-dimensionality in the 3000 gpm isosurface?

I think what you really want here is the topography of the 700 hPa
surface since that will vary across the domain of the grid.  If
you just plot geopotential height at 700 hPa, you will see that 
it is also a flat surface.  That's because the vertical dimension
in the box is altitude.  To get that plot of a pressure surface,
we convert the pressure to the height above ground in the standard
atmosphere which will be the same across the domain.

To get a  plot of the topography of the 700 hPa surface, you will
need to use the 3D Surface->Color Filled  Contour over Topography
option.  In the Field selector, select the Geopotential Height 
field and select the 3D Surface->Color-Filled Contours Over Topography
for the display.  You can select the 700 hPa level from the Level
tab in the data subset panel.  When you click "Create Display", 
you will be prompted to select the Topography field that you want
to drape this over.  From the dialog, select the Geopotential Height
field again and select the 700 hPa Level, then click OK.

Again, you will probably see that at first glance the plot looks
flat, but that's because the vertical scale in the box is 0 to 16 km
and the 700 hPa surface ranges from about 2.5 to 3.5 km.  Change
the vertical scale in the box using the View->Viewpoint->Vertical
Scale dialog and set it to 2500 to 3500 m.  Then you should see
the topography you are expecting.  Using today's model data
(e.g. GFS 80 km CONUS), you get a nice view of how the surface
dips over Hurricane Ike.

You could also drape other fields over the topography like
Temperature.  Follow the same instructions, except select
the particular field (like temperature) first, then select
the geopotential height for the topography field when prompted.

Don Murray

Ticket Details
===================
Ticket ID: GES-343526
Department: Support IDV
Priority: Normal
Status: Open