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Re: 20011218: Computing wind shear

Hi Steve,

Thanks for the reply.  I guess the answer is that there is no way to get the 
shear
for a specified layer (height AGL) depth directly using SNLIST.  The NSHARP 
display
gives the 0-2km, 0-6km etc shear vector, but I need to do it automatically.  
SNLIST
looks like it will give me an interpolated value for parameters like PRES, 
SPED, DRCT
at a specified height.  I could get the wind vectors at levels like 1km, 3km 
AGL and
then do a vector difference between the surface and that level.  Do you think 
that is
my only option with SNLIST?

thanks again,

Matt

Unidata Support wrote:

> Matt,
>
> The station elevation can be obtained with the STNDEX parameter "SELV".
> SELV is also output in the station information at the top of the output
> along with station lat/lon and time.
>
> The surface should be the first level of the sounding output. The hght of that
> levels will be the height of the station.
>
> The SHRM parameter will be the value in each layer of the sounding. That is,
> the value is calculated using each successive level of the sounding. To
> only get the the 1091km level, you would use: levels = 1091. However, the
> value of SHRM that would be output would be the shear in the layer in which
> the 1091 meter level occurs. It would not be the mean from surface to that 
> layer.
> There is no function that would give you the mean of shear in a specified 
> layer.
> The STNDEX functions allow the user to specify the layer depth and surface 
> using
> the "!" characters. However, SHRM is a level parameter, not a STNDEX function.
>
> Steve Chiswell
> Unidata User Support
>
> >From: "Matthew Menne" <address@hidden>
> >Organization: National Climatic Data Center, NOAA
> >Keywords: 200112181525.fBIFPsN07532
>
> >This is a multi-part message in MIME format.
> >--------------615C49252F8A820704026C58
> >Content-Type: text/plain; charset=us-ascii
> >Content-Transfer-Encoding: 7bit
> >
> >I would like to calculate the wind shear magnitude between the surface
> >and a specified height above ground level (AGL) and I'm not sure that I
> >am doing it correctly (using SNLIST).
> >
> >Is there a way to specify height AGL directly or do I need to know the
> >station's elevation and then add some height value to it?
> >
> >I tried the latter in an attempt to get the mean wind shear for the
> >layer 0-1km AGL for JAN (wmo=72235) whose elevation is 91 meters
> >
> >
> >   snlist << EOF
> >      snfile = ${file}_upa.gem
> >      dattim = all
> >      output = f/shear_${STN}_19${YEAR}${mon_str}
> >      snparm = SHRM
> >      stndex =
> >      levels = 91-1091-1000
> >      vcoord = hght
> >      mrgdat = y
> >      area = @${STN}
> >      r
> >
> >
> >When I run a script like the one above I get two numbers: one for 91 m
> >and another for 1091 m, but I only expected one number (the mean between
> >91 and 1091 m).  Could you help me interpret these numbers or suggest
> >how to extract the shear values that I'm looking for?  Also, is there
> >any way to obtain and use the station elevation value automatically in a
> >script somehow?
> >
> >Thanks for the help.
> >
> >
> >--------------615C49252F8A820704026C58
> >Content-Type: text/x-vcard; charset=us-ascii;
> > name="Matthew.Menne.vcf"
> >Content-Transfer-Encoding: 7bit
> >Content-Description: Card for Matthew.Menne
> >Content-Disposition: attachment;
> > filename="Matthew.Menne.vcf"
> >
> >begin:vcard
> >n:Menne;Matthew
> >tel;work:(828) 271-4449
> >x-mozilla-html:FALSE
> >org:National Climatic Data Center/NOAA;Scientific Services Division
> >version:2.1
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> >adr;quoted-printable:;;151 Patton Avenue=0D=0A;Asheville;NC;28801;USA
> >fn:Matthew Menne
> >end:vcard
> >
> >--------------615C49252F8A820704026C58--
> >
>
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