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

[Dennis Shea]

The wind barbs are 'independent' of the units. If m/s are the input units,
then the 'half-barb' is at 5 m/s, full barb is a 10 m/s, etc . If knots,
'half-barb' is at 5 knots, full barb is a 10 knots.

I am not aware of any international standard for 'wind barbs'.

On Sat, Oct 18, 2014 at 1:44 AM, 李嘉鹏 <lijpbasin at 126.com> wrote:

> 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
>
>
>
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