[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

19990510: gdcross circ function

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: 19990510: gdcross circ function
  • Date: Mon, 10 May 1999 14:29:32 -0600
John,

The OMEG values (V component of circ) will be in mb/sec.

Circ returns a vector whose U component is the tangential
component of V (in your case age()) and the V component is the
vertical motion. The cross sectional representation of the vectors
will be scaled be the aspect ratio of the plot due to the scale
exaggeration between the horizontal and vertical distances on
a plot.

To see what the values of the V component (aka omeg) are,
GFUNC    = vr(circ(age,omeg))
SCALE    = 
for todays' eta running CXSTNS   = den>bna,

shows:
 Grid file:                 $HDS/1999051012_eta_grid211.gem
 Date/time:                 f000
 Vertical coordinate:       pres
 Grid function:             vr(circ(age,omeg))
 Vector function:           circ(age,omeg)
 Endpoints:                 den>bna           Number of points:    21
 Scaling factor:        10** 3      Panel:  0                                   
                                    


 LEVELS:        -4.00    -2.00     0.00     2.00     4.00
 COLORS:            3        3        3        3        3
 LINTYP:            1        1        1        1        1
 LINWID:            1        1        1        1        1
 LABEL:             1        1        1        1        1


When scale is set to "blank" so the program picks its own, you
see that the omeg values range from -4 x10-3 to 4x10-3 mb/sec
(or roughly -4 to 4 microbars per second).

If you set SCALE=0, you see that the range is -.004 to .004 mb/sec
which is equivalent to the above -4 to 4 microbars.

Since the units aren't actually m/s, it really makes more since to
denote the vector with wind = bn rather than wind=bm.

Steve Chiswell
Unidata User SUpport




On Mon, 10 May 1999, John Egentowich wrote:

> Steve,
> I have a quick gempak question.  When I create cross sections to include      
> ageostrophic winds using "circ(age,omeg)" and displaying wind barbs in m/s -- 
>   
> are the vertical speeds scaled up?  I get cross sections that have great 
> looking
> ageo circulations however the vertical wind speeds are unreasonable.  In 
> "quiet"
> environments (without convection) I have vertical ageo wind speeds of 10-20 
> m/s.
> That can't be right unless the vertical component is scale up.  Please 
> enlighten
>  me.  Thanks for your help.
> John
> 
> ----------------------------------
> E-Mail: John Egentowich <address@hidden>
> Date: 10-May-99    Time: 07:29:37
> Phone: 919-515-1437
> ---------------------------------
>