IDV: Vertical cross section of flow vectors
IDV users,
I wanted to plot a vertical cross section of streamlines, but that
capability doesn't seem to be present in the IDV v2.0, unless I'm
missing something. Could this be another programming project for IDV
users comfortable with Jython? (I'm not there yet.)
As an alternative, I figured out how to use the existing system
formula "Make flow vectors from u, v, and w data" to plot a vertical
cross section of flow vectors. The formula requires u, v, and w
fields as input. However, the NAM and GFS model output files contain
pressure vertical velocity (omega) fields rather than w fields. Does
this mean that the formula will get the sign of the vertical
component reversed? (It certainly doesn't seem capable of converting
omega fields to w fields, given that that would seem to require the
geopotential height field at multiple times and the temperature
field, but if it got the sign right then there'd still be useful
qualitative info in the vector computed from omega and horizontal
velocity.)
I'm not an object-oriented programmer so I got lost trying to trace
the code that renders the 3-D flow vectors to see how it treats the
sign of the vertical velocity. The formula invokes the
ucar.unidata.data.grid.DerivedGridFactory class, which invokes the
createFlowVectors method, which invokes the visad class FieldImpl,
which invokes ....
Can anyone comment on what the "Make flow vectors from u, v, and w
data" formula does with u, v, and omega fields?
-- Dave
