[ncl-talk] How to specify the unit of wind speed in `skewT_PlotData`

[李嘉鹏]

Sorry about the previous message, the (HTML) formatting is terrible, post it again:

Hi,

I am trying to figure out the wind speed unit used by the `skewT_PlotData` function,
[the documentation page]
(http://www.ncl.ucar.edu/Document/Functions/Skewt_func/skewT_PlotData.shtml)
and the [skewT example page]
(http://www.ncl.ucar.edu/Document/Functions/Skewt_func/skewT_PlotData.shtml)
says the unit of the wind speed is either knot or m/s, but they are not the same:

    $ udunits2 
    udunits2: Using default XML database
    You have: knot
    You want: m/s
        1 knot = 0.514444 m/s
        x/(m/s) = 0.514444*(x/knot)

If I pass float values to the `WSPD` (`u`) and `WDIR` (`v`) argument, how do I know or
control the way `skewT_PlotData` interpret these values?

[The WMAP documentation on wind barbs]
(http://www.ncarg.ucar.edu//supplements/wmap/index.html#HEADING1-140)
indicates that the unit is knot, and [The WMAP documentation on station data]
(http://www.ncarg.ucar.edu//supplements/wmap/index.html#HEADING1-151)
mentioned a property called `UNT`, but it's not available for the `WMBARB` function.

I tried to get these information from the source code `ni/src/examples/gsun/skewt_func.ncl`,
the function `skewT_PlotData_Original` or `skewT_PlotData_Panel` does not perform unit
conversion, and the properties set for the `WMBARB` function (WDF, COL, WBA) are not related
to wind speed units.

I'll be grateful if someone can provide the exact information.

---
Regards