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[IDV #ALV-304205]: 0-6km Shear in IDV

> Thanks,
> 
> Yeah I'll have to mess around with that. I guess my main concern is that
> the "Layer Wind Shear" and "Wind Shear Vectors" formulas in the formulas
> section essentially shows zero shear in elevations that happen to be above
> the isobaric surface (the Rockies, etc.), so was trying to find a work
> around so that it's more consistent.
> 
> When I preform the Layer Wind Shear formula, I just get "s-1" as units, so
> I'm not sure on "what per second" IDV trying to plot. I was wondering if
> there was a way to convert that to knots.
> 
> 
> Thanks for your help,
> Cody

Hi Cody,

The wind shear formula in Jython:

def windShear(u, v, z, top, bottom, unit=None):
   """ calculate the wind shear between discrete layers
   <div class=jython>
   shear = sqrt((u(top)-u(bottom))^2 + (v(top)-v(bottom))^2)/zdiff</pre>
   </div>
   """
   udiff = layerDiff(u, top, bottom, unit)
   vdiff = layerDiff(v, top, bottom, unit)
   zdiff = layerDiff(z, top, bottom, unit)
#  adjust to altitude if units are gpm
   zdiff = getAltitude(zdiff)
   windDiff = sqrt(udiff*udiff + vdiff*vdiff)
   return windDiff/zdiff

So, you can actually call the windShear(u, v, z, top, bottom, unit=None): with 
a unit to do
the calculation. You can replace unit=None with Util.parseUnit("m/s") assuming 
the u and v
unit is m/s.


Yuan
> 
> address@hidden> wrote:
> 
> > > Hi,
> > >
> > > I've been working with wind shear using NARR files in IDV. The wind shear
> > > formulas given only allow the differences between isobaric surfaces (ex.
> > > 1000mb-500mb). However, wouldn't this become problematic in areas of
> > higher
> > > elevations, like towards the Rockies?
> > >
> > > So now I'm trying to plot 0-6km shear. I was able to create a formula to
> > > plot 2m to a specific pressure level. Here is the formula I have used so
> > > far for 2m-500mb Wind Shear:
> > >
> > > sqrt((make2D(v500)-make2D(v10))**2+(make2D(u500)-make2D(u10))**2)
> > >
> > >
> > > I had some 2D/3D issues initially, so I added make2D to the equation.
> > >
> > >
> > > I'm wondering if there was a way to get the program to plot the shear
> > from
> > > 2m to 6km rather than 2m to Pressure Level. The only options for the U/V
> > > Specified Height Above Ground options are 10m and 30m.
> > >
> > >
> > > I've also noticed this ordeal on the soundings. They all plot at 1000mb.
> > >
> > >
> > > Thanks,
> > > Cody
> > >
> > >
> > Hi Cody,
> >
> > The wind shear is defined as:
> >
> > shear = sqrt((u(top)-u(bottom))^2 + (v(top)-v(bottom))^2)/zdiff
> >
> > The problem is to figure out the zidff in your situation. The 2 meter
> > surface wind can be at
> > the 1502 meter altitude in the Rockies, it would be trick here to get the
> > zdiff value. You may need to write your own
> > formula. I am open to any solution.
> >
> >
> > Yuan
> >
> > Ticket Details
> > ===================
> > Ticket ID: ALV-304205
> > Department: Support IDV
> > Priority: Normal
> > Status: Open
> > ===================
> > NOTE: All email exchanges with Unidata User Support are recorded in the
> > Unidata inquiry tracking system and then made publicly available through
> > the web.  If you do not want to have your interactions made available in
> > this way, you must let us know in each email you send to us.
> >
> >
> >
> 
> 


Ticket Details
===================
Ticket ID: ALV-304205
Department: Support IDV
Priority: Normal
Status: Closed
===================
NOTE: All email exchanges with Unidata User Support are recorded in the Unidata 
inquiry tracking system and then made publicly available through the web.  If 
you do not want to have your interactions made available in this way, you must 
let us know in each email you send to us.