Correcting and enhancing AP mitigation within ORPG composite reflectivity products for FAA systems

NEXRAD Open Radar Product Generator (ORPG) composite reflectivity products (CRP) containing anomalous propagation (AP) mitigation reduce maximum reflectivity values from precipitation returns as much as 15 dBZ compared with CRP without AP mitigation. This has recently led the National Air Traffic Controllers Association to disallow CRP with AP removal from being added to controllers’ displays in Air Route Traffic Control Centers.

An examination of the AP mitigation technique, as part of the FAA's Aviation Weather Research Program (AWRP), has revealed the source of reflectivity reductions. The nature of the problem allows for a modification that neutralizes the adverse effect on precipitation returns but still removes AP as it was originally intended to do.

A set of nineteen adaptable parameters are used within the AP mitigation technique. This set was recently optimized as a result of several case studies and implemented in ORPG Build 1.2. In light of the new modification, the optimized set of parameters is once again tested to determine if any additional adjustment is required.

Focus can now shift solely on the ability of the AP technique to remove AP in a variety of meteorological environments and geographical locations. One weakness of the AP mitigation technique is reflectivity, velocity, and spectrum width information are all required at a range gate before determining if the data is AP or a precipitation return. Adjustments to the technique are being considered that require only reflectivity information before a determination is made.