Ground Scattering Analysis to Identify Targets for Refractivity Field Estimation

Efforts to estimate the near-surface moisture field using weather radar returns from coherent ground targets has been successfully demonstrated in recent years. A very crucial step to make the moisture retrieval successful is the identification of appropriate targets. The estimation process also depends on adequate spatial distribution of these targets, so it is actually more important to have a good distribution than to have every target be extremely coherent. Presently, however, there is no fully automated technique to identify the targets. The currently accepted method is to manually examine phase difference scans that span approximately an hour to identify a time period where the phase gradient is approximately the same across all azimuths. Unfortunately, this is not simple and improper selection can have drastically different results. In order to design an algorithm to automate this process, one must first understand the phase behavior of ground reflections for this purpose. Previous analysis of ground returns were for the purpose of eliminating them, but the work presented here aims to identify suitable targets for refractivity estimation.