[gradsusr] converting omega to vertical velocity

[Ricardo Hallak]

Hi Alireza,

next to surface, where the air density (rho) is about 1.2 kg/m^3, a w=1 m/s gives omg=11.8 Pa/s.
In your example, your omg~0.1 Pa/s, so it is a low value. In large-scale, the vertical motion is actually low.

In thunderstorms (and clusters of thunderstorms as well, which are mesoscale in temporal and spatial range), however, w can frequently be > 20 m/s. If you are dealing with large-scale (synoptic scale) data, your data will not be able to "see" thunderstorms.

What are the dx and dy intervals of your data? Probably your data can not explicitly resolve big vertical motions. Try to compute w in a region where there is a cold front in activity at, for example, 700 mb level.

Hope this helps,
Ricardo

On Wed, 16 Nov 2011 04:32:43 +0330, Alireza Azargoun wrote
> 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> 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
> > _______________________________________________
> > gradsusr mailing list
> > gradsusr at gradsusr.org
> > http://gradsusr.org/mailman/listinfo/gradsusr
> >
> 
> 
> --
> Tereza Cavazos
> Departamento de Oceanografia Fisica
> CICESE
> Ensenada, Baja California, MEXICO
> http://usuario.cicese.mx/~tcavazos/
> 
> _______________________________________________
> gradsusr mailing list
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> 
> 
> -- 
> Alireza Azargoun
 
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