Determining weather radar antenna pointing using signals detected from the sun at low antenna elevations

A method to determine the elevation and azimuth biases of the radar antenna using solar signals observed by a scanning radar is presented. Data recorded at low elevation angles, where the atmospheric refraction has a significant effect on the propagation of the radio wave, are used and a method to take the effect of the refraction into account in the analysis is presented. A set of equations is given by which the refraction of the radio waves as a function of the relative humidity can easily be calculated. Also, a simplified model for the calculation of the atmospheric attenuation is presented. The consistency of the adopted models for the atmospheric refraction and atmospheric attenuation is confirmed by data collected at a single elevation pointing, but over a long observing time. Finally, the method is applied to data sets based on operational measurements at FMI and KNMI, and elevation and azimuth biases of the radars are shown.