Performance of an airborne radar turbulence detection algorithm

Encounters with convective turbulence continue to be a key factor in commercial transport accidents. Providing accurate short-term forecasts of these turbulence events is not yet a reality; hence, the ability to detect and warn pilots of an impending encounter is important. Many commercial transport aircraft are currently outfitted with a predictive windshear radar system. Therefore, as part of the U.S. National Aeronautics and Space Administration’s (NASA) Aviation Safety Program (AvSP), the Turbulence Prediction and Warning System (TPAWS) team has developed real-time detection algorithms that can provide timely and accurate warnings of convective turbulence in low reflectivity situations (<30 dBZ). In the near-term, only software modifications to the existing radar systems will be implemented and NASA is working with the radar manufacturers, FAA and airlines to expedite the certification of this technology.

As part of the these R&D activities, the National Center for Atmospheric Research (NCAR) has developed new turbulence detection and data quality control algorithms for use with airborne radars. A brief description of these algorithms is presented, along with verification results. A thorough verification exercise was performed in 2001 using NASA’s 757 research aircraft. Fifty-five cases were analyzed by a team of human experts. Forty-two of these cases contained moderate of greater turbulence encounters. A comparison of the radar-based turbulence algorithm and in situ aircraft data shows that the current algorithm can provide reliable detection well in front of the aircraft, even at very low reflectivities.