Polarimetric

POLARISATION - Orientation of the electrical field component of an electromagnetic wave
  • Linear (horizontal / vertical)
  • Circular

Determines what type of target is best detected by the radar

Weather Watch Radar usually uses linear horizontal polarisation

Dual polarisation (polarimetric) can determine attenuation, drop size distribution etc. – the future radar

Polarization is a result of the conversion of electrical energy to electromagnetic energy by rapidly varying the polarity of the magnetic dipole

Weather Radars generally employ linear horizontal pulses

Most uses are in the detection of rainfall (horizontally larger due aerodynamic flattening)

Major advantages

  1. Recognition of AP and ground clutter. Rayleigh scatter of spherical raindrops vs non Rayleigh scatter of non-sphere shaped ground clutter
  2. Improved rainrate estimates when rain alone is present. Knowing DSD allows better estimates of R = ∑ND3.67and Z = ∑ND6
  3. Improved rainfall estimates when ice is present. Special signatures of hail and snowflake. Without the info, one overestimate, the other underestimate.
  4. Correction for attenuation. Attenuation is proportional to drop size.
  5. Identification of hydrometeors.