Linda

							Effects of Radar Sampling
    on Single-Doppler
  Velocity Signatures of
    Mesocyclones and
        Tornadoes
Mesocyclone Velocity Signatures
• When beam width widens, Doppler
  velocities are degraded
• Pattern of mesocyclone signature fluctuates
  as angular separation changes:
     • Azimuthal separation of the extreme measured
       velocities and size of the core
     • Deduced diameter increases
     • Mean rotational velocity decreases
        Mesocyclone
Rotational Velocity Vs Range
     Tornadic Vortex Signature
• Detection is a function of the diameter core,
  strength and size of the radar sampling
  volume
• Smearing effects of a large radar beam on a
  small tornado vortex:
     • Deduced azimuthal diameter is overestimate
     • Peak rotational velocity is underestimated
           Tornado
Rotational Velocity Vs. Range
             TVS continued
• At 5km
  – Represents a tornado because of diameter of
    beam
  – Deduced core diameter and rotational velocities
    are close to actual value
  – Does not produce significant differences in
    single-Doppler velocity pattern
             TVS continued
• At further distances
  – Radar sampling does affect the appearance of
    Doppler velocity
  – Changes magnitudes and locations of mean
    Doppler velocity peaks
               Conclusion
• Random position of the radar beam can
  change the magnitude and location of peak
  Doppler velocity values
• Variations may be due to evolution or
  chance position of the radar beam relative to
  the vortex’s maximum rotational velocities