CASA
CASA Main Home Page
 CASA OU Page
 

This page is for collaborating my contributions to the CASA Project



(02.23.05)

Currently I am working on providing a Tornado Vortex Signature (TVS) Detection Algorithm (TDA) "Lite" version for the CASA Project. 

Due to the potentially close proximity of a tornado to the radar(s), we are incorporating a version of the National Severe Storms Laboratory's (NSSL) Mesocyclone Detection Algorithm (MDA) instead of the NSSL TDA.  This is because the TDA searches for areas of maximum gate-to-gate velocity differences that would meet TVS thresholds.  Compare this WSR-88D TVS to what we anticipate the CASA radar will be sampling.

The NSSL MDA* consists of 4 basic steps:

  1. Locate runs of increasing azimuthal velocity across adjacent radar gates.  This process of identifying cyclonic "shear segments" is considered 1D processing.
  2. After 1D processing is complete, identify clusters of shear segments that meet certain range-dependent threshold criteria on the same elevation scan.  This is known as 2D processing.
  3. At the end of a volume scan, look for vertical association of 2D features.  This is 3D processing.
  4. For consecutive volume scans, identify 3D features from previous scans that fit storm motion criteria.  This is the time association, or 4D processing.
I have completed the 1D processing (except for dbZ thresholding) and provide examples in the table below.  The examples show the Doppler radar velocity in the left panel and the respective product in the right panel.

*Gregory J. Stumpf, Arthur Witt, E. DeWayne Mitchell, Phillip L. Spencer, J. T. Johnson, Michael D. Eilts, Kevin W. Thomas and Donald W. Burgess. 1998: The National Severe Storms Laboratory Mesocyclone Detection Algorithm for the WSR-88D. Weather and Forecasting: Vol. 13, No. 2, pp. 304–326.
Product
 Description
 Link
MDA 1D Max Velocity Difference
 The difference between the max and min velocities in a shear segment.   (m/s)
 delta_v
MDA 1D Max Gate-to-Gate Velocity Difference
 The maximum gate-to-gate velocity difference within the shear segment.   (m/s)
 gtg_delta_v
MDA 1D Shear
 The shear ( Velocity Diff / Segment Length) of the segment.   (m/s/km)
 shear
MDA 1D Strength Rank
 The strength rank of the segment.   (non-dimensional) strength_rank