[gradsusr] converting omega to vertical velocity

[Alireza Azargoun]

Dear Mai, Mason and Ricardo
I really appreciate your help since I'm not familiar with the subject. now
i understand the trends in the equation. i had checked out the results in
different levels ( including 700mb). but all these values were about the
same order ( 10^-3 (m/s) ). I'm using reanalysis data of NCEP from the
following link:

html <http://dss.ucar.edu/pub/cfsr.html>http://dss.ucar.edu/pub/cfsr.html

I'm trying to use this data to compute vertical velocities of air which
affect the airplanes passing through these air parcels. (I don't think
values below 1 (m/s) have any effects on airliners) . but it seems either I
used a wrong datasets which cannot simulate reality conditions or these
downwash and upwash streams are local and rapid changes which can't be
found in any datasets!
Regards,
Alireza


On Wed, Nov 16, 2011 at 4:51 AM, Ricardo Hallak <hallak at model.iag.usp.br>wrote:

>  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
>> > gradsusr at gradsusr.org
>> > http://gradsusr.org/mailman/listinfo/gradsusr
>> >
>
>
> >
>
> > --
> > Alireza Azargoun
>
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>


-- 
Alireza Azargoun
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