Differential reflectivity calibration and antenna temperature

Using data from the Multi-Angle Snowflake Camera-Ready (MASCRAD) Experiment, S-Pol measurements over extended periods reveal a significant correlation between the ambient temperature at the radar site and the Z(dr) bias. Using radar scans of the sun and the ratio of cross-polar powers, the components of the radar that cause the variation of the Z(dr) bias are identified.

It is postulated that the thermal expansion of the antenna is likely the primary cause of the observed Z(dr) bias variation. The cross-polar power (CP) Z(dr) calibration technique, which is based on the solar and cross-polar power measurements, is applied to data from the Plains Elevated Convection at Night (PECAN) field project. The Z(dr) bias from the CP technique is compared to vertical-pointing Z(dr) bias measurements, and the uncertainty of the Z(dr) bias estimates is given.