An automated algorithm for radar beam occultation

The deployment of the Weather Surveillance Radar – 1988 Doppler (WSR-88D) network has provided weather forecasters critical information for issuing warnings on the occurrence of tornadoes, severe storms, and flash floods. Accurate beam blockage information is very important to all radar data applications, especially in mountainous regions. The National Severe Storms Laboratory (NSSL) has developed an automated algorithm that calculates beam occultation based on terrain, radar beam pattern (or power density function), and radar beam propagation path. The algorithm has been used to develop beam occultation data sets for all the WSR-88D radars using 1 arc seconds DEM (digital elevation model) data. The algorithm is independent of radar types (e.g., WSR-88D, Terminal Doppler Weather Radar, etc) and of radar scan strategies.

A new project (an extension of the automated algorithm) is undergoing to develop seasonal and diurnal beam occultation data sets based on reflectivity climatology and to study non-standard beam propagations under different atmospheric thermodynamic conditions. The algorithm and example occultation data from selected radars will be presented at the workshop.