[Wrf-users] Query Reg Surface wind speed and direction from WR F

Sam Hawkins s.hawkins at ed.ac.uk
Tue Aug 17 09:29:39 MDT 2010


I don't think you will see any difference when using a Mercator projection.

As far as I understand, U and V refer to wind speed components relative
to the model grid. If you are using a projection such as a rotated polar
stereographic projection, the model's x and y axes will not align
west-east and south-north. In this case, to find the Earth relative
winds, U and V must be rotated using the variables SINALPHA and
COSALPHA.   This is done  automatically for the U10 and V10 variables.

When using a Mercator projection, the model grid will align west-east
and south-north, so there will be no difference between the two.


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>    1. Query Reg Surface wind speed and direction from WR F (Geeta Geeta)
> ----------------------------------------------------------------------
> Message: 1
> Date: Mon, 16 Aug 2010 07:31:54 +0000
> From: Geeta Geeta <geeta124 at hotmail.com>
> Subject: [Wrf-users] Query Reg Surface wind speed and direction from
> 	WR F
> To: wrf users group <wrf-users at ucar.edu>
> Message-ID: <BLU152-w22758D9B5136DAA49DA4688A9B0 at phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
> Dear WRF Users. 
> This is Query Reg Surface wind speed and direction from WRF. 
> I am getting the U10 and V10 (the ROTATED wind components) as one of the diagnostics from WRF. I have used mercator projection for the domain. 
> Also,
> ws10 and wd10, are the Wind Speed (m s-1) and Direction (Degrees) at 10
> M  is also available as one of the outputs. What is the Difference
> between the two. 
> Pls clarify how to compute the actual wind speed and direction at a particular point. 
> I have plotted all the 3 variables ie, the U10 and V10, and wd10 (attatched wind.gif). 
> ga-> d skip(U10,2,2);V10
> ga-> c
> ga-> set cint 20
> cint = 20 
> ga-> d wd10
> Contouring: 20 to 340 interval 20 
> ga-> d skip(U10,2,2);V10
> ga-> printim wind.gif
> I am unable to find any significant difference between the U10;V10 and the ws10 and wd10. 
> Pls clarify this doubt. 
> geeta
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Sam Hawkins
Institute for Energy Systems
School of Engineering and Electronics
The King's Buildings
University of Edinburgh
0131 6505612

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