Comparison of Turbulence Indicators Obtained from In Situ Flight Data

Two indicators of turbulence—the eddy dissipation rate (EDR) and derived equivalent vertical gust velocity (DEVG)—are calculated using aircraft observations from Hong Kong–based airlines, whose aircraft included Boeing and Airbus models, for 39 months from February 2011 to April 2014. Characteristics of the two turbulence indicators that were calculated at 1-min intervals from the flight data are investigated. For Boeing and Airbus aircraft, there are large seasonal variations in the 90th and 99th percentiles of EDR and DEVG, whereas there are relatively small seasonal variations in the medians of EDR and DEVG. For the turbulence encounters estimated from EDR and DEVG, the authors compute their correlations for each level of turbulence and each type of aircraft. Strong correlations (larger than 0.7) occurred for all levels of turbulence encounters for Boeing aircraft, whereas relatively weak correlations (less than 0.5) occurred for Airbus aircraft. This difference is due to the different characteristics of recorded Boeing and Airbus aircraft data (the number of decimals and data sampling frequency). Based on correlation analyses, the authors construct the best-fit curves using mean EDR values for each DEVG bin and mean DEVG values for each EDR bin and obtain relationships between EDR and DEVG for Boeing and Airbus aircraft. The EDR and DEVG-derived EDR for moderate-or-greater-level turbulence are generally similar for Boeing aircraft.