From wlee@stout.atd.ucar.edu  Wed Aug  2 13:58:34 1995
From: wlee@stout.atd.ucar.edu (Wen Chau Lee)

Subject: ELDORA data


Hi, VORTEX participants:

I would like to setup a communication channel to document problems and
solutions of VORTEX ELDORA data.  I hope that everyone reports problems
and solutions(?) to ELDORA (eldora@stout.atd.ucar.edu).  These messages 
will be sent to appropriate ELDORA staff.  If you wish to address your
question to a specific person, please mention his/her name in your message.
The confirmed problem will be archived and its solution (if we come up one) 
will be announced to this distribution list. If you know anyone that 
should be or wish to be on this list or if you wish to be taken off this
list, please let me know. The following is 
an example on how we may communicate in the future. 

From: Wen-Chau Lee
To: VORTEX participants
Subject: Unfolding problems and its solution

A bug has been identified in calculating unfolded velocity VR from VL
and VS (velocities from individual PRFs). This error only affects 
VR when abs(VL-VS)> 31.2 (fore) and 31.866 (aft) which is caused by 
improperly handled angle differences near pi and -pi. This error affected 
velocities between VLny and VSny (nyquist velocities of large PRF and 
small PRF) or -VLny and -VSny. In the usual operation mode (Nyquist 
velocity of +-79 m/s), the PRFs are 2500 and 2000 (VLny=19.502 m/s and 
VSny=15.6 m/s for fore radar, VLny=19.916 m/s and VSny=15.933 m/s for 
aft radar). The slight differences in Nyquist velocities between fore 
and aft radars are caused by the differences in frequencies. So this 
problem occurred roughly 16<VR<19.5 and -19.5<VR<16 that created some
speckles in the data.

The solution is to identify abs(VL-VS) > 31.2 and 31.866, and recalculate 
VR from VL and VS. An editing function will be added in solo to deal with 
this problem. It will take a few days to complete this addition. Stay tune. 

This problem is different from the speckles caused by high spectrum 
width. However, the solo editing function may be able to correct part
of the high spectrum width speckles. If you know the correct Nyquist 
interval, you can recalculate VR using the appropriate equation.



Distributions:

UCLA
      Roger Wakimito
      Nolan Atkins
      Ching-Hwang Lie

U of Oklahoma:
      Howie Bluestein
      Steve Gaddy

NSSL 
      Irv Watson

NCAR/ATD
      Peter Hildebrand
      Craig Walther
      Dick Oye
      Mitch Randall
      Eric Loew
      Rich Neitzel
      Sherrie Smith
      Robert Rilling
      Susan Stringer
      Rick Parsons
      Cindy Mueller
      Jon Corbet