[RegCNET] Wind direction

[bixq]

On Fri, 27 Aug 2010, Smz Rcm wrote:

> I need to know the speed and the direction of wind. For speed, I can
> know it by ua and va or by wx10m, but I did not find a parameter wich 
> tells about direction (value between 0 and 360).
>
> This is my need actually
>

After you rotate the wind direction to a uniform lat-lon grid
(for example, you run the regrid for RegCM4 output), let's say
you get new fields u and v.

suppose u < 0 and v = 0, it is easterly wind, angle=180

suppose u = 0 and v < 0, it is southward wind, angle=270

......

angle = arctan (v/u)

> --- En date de : Jeu 26.8.10, bixq <bixq at ictp.it> a écrit :
>
> De: bixq <bixq at ictp.it>
> Objet: Re: Wind direction
> À: "Smz Rcm" <smzrcm at yahoo.fr>
> Cc: regcnet at lists.ictp.it
> Date: Jeudi 26 août 2010, 16h50
>
>
> Hi,
>
> I think the wind direction at the center of your domain is not required to
> be rotated. For LAMCON and ROTMER projection, for those points far away from the center are required to rotate the wind direction if you want to
> compare with the lat-lon grid data.
>
>
> On Thu, 26 Aug 2010, Smz Rcm wrote:
>
>> Dear all,
>>
>> I turned the model RegCM3 with ECHAM50 and need to extract the wind direction in the central point, but don't know how!
>>
>> Please can you help me?
>>
>> Cordially
>>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   Dr. Xunqiang Bi         email:bixq at ictp.it
>   Earth System Physics Group
>   The Abdus Salam ICTP
>   Strada Costiera, 11
>   P.O. BOX 586, 34100 Trieste, ITALY
>   Tel: +39-040-2240302  Fax: +39-040-2240449
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Dr. Xunqiang Bi         email:bixq at ictp.it
   Earth System Physics Group
   The Abdus Salam ICTP
   Strada Costiera, 11
   P.O. BOX 586, 34100 Trieste, ITALY
   Tel: +39-040-2240302  Fax: +39-040-2240449
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~