20030512: Cross section terrain

Dave,

When plotting a cross section, the X-Z grid box is missing if
one of the end points is below ground, which will be the case when
the terrain rises above the horizontal level. The box spacing in the
horizontal will be affected by your model grid spacing, and
the vertical will be affected by the vertical levels you have.

The contouring program does not perform a one sided interpolation of the
data to the approximate position of the topography.

You can improve your graphic by increasing the vertical levels (looks like
every 50Mb in your plot) by using GDVINT to interpolate to a finer
vertical resolution in the lowest layers where you experience the
terrain effect.

Steve Chiswell

On Mon, 12 May 2003, David Novak wrote:

> Hello -
>
> In creating cross sections in GEMPAK from Eta model data I am seeing
> missing data close to the ground where the model terrain rises to or
> above model levels. This results in a stepped appearance to the data
> rather than continous data down to the ground. I've attached a figure
> in which the problem is most evident in panels b and d. I ran gdlist to
> see if the model data was indeed there at those pressure levels and it
> appeared to be present. My question is are there any variables that
> would allow one to plot data continously down to the ground, or is this
> how the GEMPAK plotting routine works?
>
> Thanks,
> Dave
>