Streamline Density


I've been looking at the quality of streamline analyses (of atmospheric wind fields) lately.

I was experimenting with streamline displays in the McIDAS system, and thought (IMHO) that the streamline analyses looked better as the density of the streamlines increased.

I then tried to increase the density of the streamlines in a visad display, and but wasn't able to generate the same density as the McIDAS display.
Should I be able to do this? If so how?

Tried changing "streamlineDensity" from the default of 1.0 to higher values of 10.0, 100.0, 1000.0 and 1000.0, but didn't notice much change beyond 100.0.

Further details:
1) In McIDAS I did this:
GRDDISP <modelname> FHOUR=0 PARAM=STREAML LEV=SFC LAT=-20 20 LON=-160 -100 CINT=0 COLOR=15

Image is attached as "mcidas_streamline.png"

2) In Visad/jython I did this:

maps = (xMap, yMap, rngUMap, rngVMap)

disp = subs.makeDisplay(maps)
flowcontrol = rngUMap.getControl()
strmDensity = flowcontrol.getStreamlineDensity()
stepFactor = flowcontrol.getStepFactor()
print " streamline density " , strmDensity, " stepFactor ", stepFactor

drLAPSuv=subs.addData("windbarbs", uv, disp)

Image is attached as "visad_streamline.png"



James Kelly Australian Bureau of Meteorology

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