Radar measurements may be affected by errors such as calibrations errors (in reflectivity (Z_h) and differential reflectivity (Z_dr) ), attenuation and differential attenuation. Any type of study that involves these measurements should be sure that these errors have been properly corrected.

Z_dr is easy to calibrate by pointing the radar at the vertical during a rain event, preferably with weak winds. If raindrops fall steadily, their dimensions seen from below should all be similar, producing a 0dB Z_dr. Reflectivity may be calibrated through a method that uses the redundancy of the polarimetric variables in rain. The specific differential phase (K_dp), defined as the range derivative of the differential phase shift Phi_DP, is immune to calibration errors. Combined, the three variables Z_h, Z_dr and K_dp provide redundant information in rain, and this characteristic is used to calibrate Z_h (provided that Z_dr was previously calibrated). We will also attempt to calibrate using a more classical approach: using a metal sphere attached to a tethered balloon. Knowing the size of the sphere, and the distance from the radar we can calculate the theoretical value for reflectivity and compare with the measured reflectivity.

Attenuation and differential attenuation are corrected using Phi_DP, which has been shown to be proportional to the attenuation and differential attenuation coefficients (a_h and a_d respectively). We calculate a_h and a_d for each radial, instead of using the same coefficients for the whole domain. This should produce a more realistic correction, especially in cases of convective rain, since attenuation is stronger along the radial where rainfall is heavier.

Examples and results from each of these methods will be presented