Inter-comparison and potential synergies of three methods for weather radar antenna pointing assessment

Abstract

Three methods for estimation of the weather radar antenna azimuth and elevation pointing offsets are compared. Two of the methods reviewed use the known location of the sun as a reference. The first of these methods is based on an offline scan of the sun disk. The second method detects and characterizes solar interferences in operative scans. The third method consists of correlating measured ground clutter echoes with echoes simulated using a high-resolution digital elevation model. The main objectives are to review the characteristics in each case, studying their performance in actual operative conditions, and to examine the reasons for the discrepancies between the reported pointing bias estimates, with the aim of laying the groundwork for an optimized individual or combined application and interpretation of the methods. Daily pointing biases estimated through the sun-scanning procedure in a dedicated one-month, short-term campaign are the base for the intercomparison. When applied to the three weather radars operated by the Meteorological Service of Catalonia, the short-term study reveals the advantages and limitations of the methods. A one-year, long-term analysis serves to confirm and clarify the discrepancies inferred from the short-term study and highlights how the antenna position at the time of the measurement may influence the pointing bias estimates. Based on the long-term results, a combination of the two sun-based methods for detection and simultaneous quantification of the pointing bias and the system leveling error is discussed.