Interpretation and use of NTDA page

The NCAR Turbulence Detection Algorithm (NTDA) provides a 3-D radar-based product that identifies regions of in-cloud turbulence. NTDA provides a measurement of atmospheric turbulence intensity called eddy dissipation rate, EDR. EDR has units m2/3 s-1.and is the ICAO standard quantity for atmospheric turbulence. NTDA differs from ITFA in that NTDA uses Doppler radar data to provide a current picture of detected in-cloud turbulence, including convective turbulence, whereas ITFA uses WRF model data to provide forecasts of turbulence, particularly clear air turbulence. The two products are complementary. The specific NTDA EDR threshold values for each turbulence intensity category are: Smooth: NTDA EDR < 0.15 Light: 0.15 ? NTDA EDR < 0.30 Moderate: 0.30 ? NTDA EDR < 0.50 Severe: 0.50 ? NTDA EDR < 0.70 Extreme: 0.70 ? NTDA EDR Similar to ITFA, the NTDA intensity categories are tuned for large to heavy aircraft, with a B757 being in about the center of the range. Heavy aircraft include B757, B767, B777, B747, A300, A310, A330, and A340. A B737 is in the large or medium category. The ICAO categorizes aircraft as follows: Heavy: weight ? 136,000 kg (300,000 lbs) Medium or Large: 7,000 kg < weight < 136,000 kg Light: weight ? 7,000 kg (15,400 lbs)

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