Attenuation correction of Z overview

In dual-polarization radars, the measurements consist of measuring the amplitude and phase of the received waveforms in the two separate channels. PhiDP is the phase difference between the two polarization channels at each range bin.

The PhiDP quantity primarily comes from the propagational effects as the RF energy passes through some medium to the measurement point and back again to the transmitter/receiver. The PhiDP measurement tends to be a noisy, unstable quantity, due to the slightly different backscattering phase shifts from the scatterers at the range point and statistical measurement errors.

The unambiguous range of PhiDP is 360° in the simultaneous operation mode. However, phase changes of more than 360° are common, especially with smaller wavelength radars, and cause PhiDP to be phase wrapped.

PhiDP is directly related to the amount of liquid water content the transmitted energy passes through to get to the scatterers at a specific range bin. Therefore, PhiDP has advantages when used to estimate attenuation caused by liquid water. In dual polarization radars, the range derivative, or specific differential phase (Kdp) is also a key data type to indicate rainfall rates.

Before to using PhiDP for any of these applications, it must be conditioned and unfolded. Here, conditioning means to smooth out the inherent noisy properties of the data, yet be able to capture and maintain the range and amplitude resolution common within intense rain cells. See PHiDP Unfolding and Conditioning.

The conditioned PhiDP is fed to:

After these are applied, the IRIS and RDA software makes optimal use of the dual-channel measurements, creating data types for the following applications:

  • Hydrometeor particle identification
  • Lightning hazard potential forecasting
  • Detection of convection and stratiform rain
  • Highway snow removal
  • Airport terminal operation
  • Rain/snow line demarcation
  • Melting height detection
  • Weather modification for hail mitigation
  • Insurance industry claims verification
  • Military detection of chaff
  • Data quality improvement by elimination of non-meteorological targets
  • Improved precipitation forecasting
  • Hydrological modeling

Dual-polarimetric attenuation correction is a collection of algorithms, which may be performed in real-time, in the RVP10 signal processors, or in the IRIS application software. See Dual-polarimetric attenuation correction.