Remote detection of turbulence using ground-based Doppler radars

Real-time remote detection of in-cloud turbulence would provide a valuable new input to decision support systems that help pilots and air traffic controllers assess weather-related aviation hazards, and in particular offers the potential to improve safety and air traffic flow during convective events. This capability may be provided, in part, by a new Doppler radar turbulence detection algorithm designed for use on the operational NEXRAD and TDWR radars that effectively cover the continental US. The new fuzzy logic algorithm, developed at NCAR under the auspices of the FAA's Aviation Weather Research Program, makes use of the radar-measured reflectivity, radial velocity, and spectrum width to perform data quality control and produce estimates of eddy dissipation rate (EDR), an aircraft-independent turbulence metric. It is anticipated that the algorithm will eventually be installed on all NEXRAD and TDWR radars, and that the radar-derived EDRs will be combined with satellite, in situ, and numerical weather model data to produce a nationwide integrated turbulence detection product.

In addition to describing the new turbulence detection algorithm, the authors present highlights of the verification process that has demonstrated the algorithm's skill and potential operational utility. This process has included extensive comparisons of radar-derived EDR estimates with in situ EDR values obtained from aircraft winds data, including both post-processed data from the NASA Boeing 757's spring 2002 flight tests and EDRs produced by an automated turbulence reporting system developed by NCAR and currently operating on a number of commercial aircraft. In addition, analysis of Flight Data Recorder information provided by the NTSB shows that the NCAR turbulence detection algorithm often detected hazardous in-cloud turbulence well in advance of the aircraft encounter.