[gradsusr] converting omega to vertical velocity

[Rowell, Mason D.]

Hello,

What Tereza means is that typical synoptic scale vertical motion is on the order of cm/sec, or 10^-2m/sec. If you covert your W to these units you get something very near 1 cm/sec, so synoptically speaking, there is nothing wrong with this magnitude. I do know that this conversion formula that you are using is based on synoptic scaling arguments and thus ignores other effects that need be taken into account as well for different scales of motion. I believe those effects are upslope motion (possibly) and also that the local pressure tendency, both of which are ignored or assumed small for synoptic application. I will crack open my synoptic meteorology book when I get a chance to confirm this, but if your scales of motion are not synoptic you may want to include other terms in your conversion, then maybe you might get a W value about as large as you are expecting for the scale your operating on. Hope this helps! Again, I'll confirm what my memory limits me to as of right now come tomorrow.

Mason
________________________________
From: gradsusr-bounces at gradsusr.org [gradsusr-bounces at gradsusr.org] on behalf of Alireza Azargoun [alireza.azargoun at gmail.com]
Sent: Tuesday, November 15, 2011 7:02 PM
To: GrADS Users Forum
Subject: Re: [gradsusr] converting omega to vertical velocity

thnx Tereza

but I don't understand it. did you mean that my answer [W=0.00912 (m/s)]  is not (m/s) and it's in (cm/sec)!? supposing that isn't a 0.912 cm/sec a low speed vertical velocity airflow!? if there's any reference on this subject I'll be glad if you anyone notify me about it.

On Wed, Nov 16, 2011 at 4:18 AM, <tcavazos at cicese.mx<mailto:tcavazos at cicese.mx>> wrote:
Hi

The usual unit (magnitude) of vertical velocity is in cm/seg.
So, it is fine.

Cheers,
Tereza

> Dear GrADS users
> Hi
>
> I'm recently working on a project about the vertical speed of air in
> different elevations. I'm using CFSR data in grb2 format. these data sets
> have omega (Pa/s) instead . I tried to convert them to vertical velocity
> (m/s) using this equation:
> omega=  - rho * g * w  ( or omega=- (P/RT) *g * w )
> but the results in (m/s ) are in the order of 10^-3. I know it's not a
> Grads problem. but I'm an aerospace student and I need to find out if
> anything is wrong with this equation or the results or not. ( I'm not
> really familiar with meteorology!)
>
> for example:
> if  omega= 0.10595
> & g=9.807
> & R=287
> & P= 100000 Pa
> & T=294.27
> resulted value is W=0.00912 (m/s)
>
>
> Thanks in advance,
> Alireza
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--
Tereza Cavazos
Departamento de Oceanografia Fisica
CICESE
Ensenada, Baja California, MEXICO
http://usuario.cicese.mx/~tcavazos/<http://usuario.cicese.mx/%7Etcavazos/>

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--
Alireza Azargoun
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