Characteristics of the derived energy dissipation rate using the 1 Hz commercial aircraft quick access recorder (QAR) data

Abstract

The cube root of the energy dissipation rate (EDR), as a standard reporting metric of atmospheric turbulence, is estimated using 1 Hz quick access recorder (QAR) data from Korean-based national air carriers with two different types of aircraft (Boeing 737 (B737) and Boeing 777 (B777)), archived for 12 months from January to December 2012. The EDRs are estimated using three wind components (zonal, meridional, and derived vertical wind) and the derived equivalent vertical gust (DEVG) of the 1 Hz post-flight data by applying all possible EDR methods. Wind components are used to calculate three different EDRs, utilizing the second-order structure function, power spectral density, and von Karman wind spectrum and maximum-likelihood method. In addition, two DEVG-based EDRs are calculated using the lognormal mapping technique and the predefined parabolic relationship between the observed EDR and DEVG. When the reliability of lower-rate (1 Hz) data to estimate the EDR is examined using the higher-rate (20 Hz) wind data obtained from a tall tower observatory, it is found that the 1 Hz EDR can be underestimated (2.19 %-12.56 %) or overestimated (9.32 %-10.91 %). In this study, it is also found that the structure-function-based EDR shows lower uncertainty (2.19 %-8.14 %) than the energy spectrum-based EDRs (9.32 %-12.56 %) when the 1 Hz datasets are used. The observed EDR estimates using 1 Hz QAR data are examined in three strong turbulence cases that are relevant to clear-air turbulence (CAT), mountain wave turbulence (MWT), and convectively induced turbulence (CIT). The observed EDR estimates derived from three different wind components show different characteristics depending on potential sources of atmospheric turbulence at cruising altitudes, indicating good agreement with selected strong turbulence cases with respect to turbulence intensity and incident time. Zonal wind-based EDRs are stronger in the CAT case that is affected by synoptic-scale forcing such as upper-level jet/frontal system. In the CIT case, vertical wind-based EDRs are stronger, which is related to convectively induced gravity waves outside the cloud boundary. The MWT case has a peak of the EDR based on both the zonal and vertical winds, which can be related to the propagation of mountain waves and their subsequent breaking. It is also found that the CAT and MWT cases occurred by synoptic-scale forcing have longer variations in the observed EDRs before and after the turbulence incident, while the CIT case triggered by a mesoscale convective cell has an isolated peak of the EDR. Current results suggest that the 1 Hz aircraft data can be an additional source of the EDR estimations contributing to expand more EDR information at the cruising altitudes in the world and that these data can be helpful to provide a better climatology of aviation turbulence and a situational awareness of cruising aircraft.