Statistical Analyses of Aviation Turbulence Encounters Revealed in Aircraft Observations

Using observational data from Korean Air Lines (KAL) Boeing (B) 737-800, B777-200, and B777-300 from January to December 2012, the derived equivalent vertical gust velocity (DEVG) is calculated as a turbulence indicator. KAL-DEVG is used to evaluate of the operational Korean aviation Turbulence Guidance (KTG) system developed using a combination of the Regional Data Assimilation and Prediction System (RDAPS) of the Korea Meteorological Administration and pilot reports (PIREPs) over East Asia where the observed MOG KAL-DEVG appears mainly following the jet stream. Based on one-minute segments of the calculated DEVG, the highest frequency of moderate-or-greater (MOG) turbulence occurs in the northern hemisphere winter, while the lowest occurs in the northern hemisphere summer. Spatially, KAL-DEVG covers five regions in Asia, Oceania, Western Europe, North America, and South America following major flight routes. Because of variations in the flight density and navigation time, KAL-DEVG is normalized by these factors. Nearly 1 MOG turbulence is observed per flight and per 10 hours of navigation. The forecasting performance evaluated by the skill score (defined as the area under the curve (AUC) based on the probability of detection statistics) on the operational-KTG system against KAL-DEVG and RDAPS analysis data is found to be 0.815, with a 95% confidence bounds ranging from 0.812 to 0.821. Using the RDAPS 6-hour and 12-hour forecast data, the skill score is slightly less than 0.8 against KAL-DEVG, while it is larger than 0.8 against PIREPs.