Iterative PhiDP Correction

For segments identified as rain, a first guess of intrinsic reflectivity is created. The approach is to use the same expression seen in Equation 2 in Dual-polarimetric attenuation correction, but substituting the change of PhiDP from the beginning to the end of the segment for Z.

This appears as:

Equation 3

dBZc = dBZc + 2C∆r ∑ (θr min-θr max)E

For the first rain segment nearest to the radar, the system PhiDP values are initially set by a configuration setting in the RVP10 dspx menus. However, this system PhiDP value is constantly updated with the average PhiDP values seen in the first bins of the rain segments.

The initial guess of the intrinsic reflectivity is adjusted using an iterative process, which is constrained by the total attenuation along the entire radial. The total attenuation is now determined by:

Equation 4

A = ½ αh ∆ ΦDP

where the α coefficient is a constant, slightly dependent on temperature. The adjustment is performed by using the ratio of the total attenuation and a summation of measured reflectivity values to the particular range bin to scale the correction.

Equation 5

d B Z c = d B Z ( r ) + A ∑ r = min ⁡ r = max ⁡ 10 0.1 b ( d B Z ( r − 1 ) ) ∑ r = min ⁡ r ⁡ 10 0.1 ( d B Z b ( r − 1 ) )

In this manner, the sum of the corrections applied to each range bin are equivalent to the total attenuation, as determined by ∆ΦDP.

This first guess of intrinsic reflectivity, sometimes called the DP method, may be output from IRIS or the RVP10 software for research purposes. For operational radars, the full IDPC methodology should be used and is the default selection.