Atmospheric turbulence at commercial aircraft cruising altitudes is a main threat to aviation safety worldwide. As the air transport industry expands and is continuously growing, investigating global response of aviation turbulence under climate change scenarios is required for preparing optimal and safe flying plans for the future. This study examines future frequencies of moderate-or-greater-intensity turbulence generated from various sources, viz., clear-air turbulence and mountain-wave turbulence that are concentrated in midlatitudes, and near-cloud turbulence that is concentrated in tropics and subtropics, using long-term climate model data of high-emissions scenario and historical condition. Here, we show that turbulence generated from all three sources is intensified with higher occurrences globally in changed climate compared to the historical period. Although previous studies have reported intensification of clear-air turbulence in changing climate, implying bumpier flights in the future, we show that intensification of mountain-wave turbulence and near-cloud turbulence can also be expected with changing climate.

A commercial aircraft, departing from Seoul to Jeju Island in South Korea, encountered a convectively induced turbulence (CIT) at about z = 2.2 km near Seoul on 28 October 2018. At this time, the observed radar reflectivity showed that the convective band with cloud tops of z = 6–7 km passed the CIT region with high values of spectral width (SW; larger than 4 m s^–1). Using the 1 Hz wind data recorded by the aircraft, we estimated an objective intensity of the CIT as a cube root of eddy dissipation rate (EDR) based on the inertial range technique, which was about 0.33–0.37 m^2/3 s⁻¹. Radar-based EDR was also derived by lognormal mapping technique (LMT), showing that the EDR was about 0.3–0.35 m^2/3 s⁻¹ near the CIT location, which is consistent with in situ EDR. In addition, a feasibility of the CIT forecast was tested using the weather and research forecast (WRF) model with a 3 km horizontal grid spacing. The model accurately reproduced the convective band passing the CIT event with an hour delay, which allows the use of two methods to calculate EDR: The first is using both the sub-grid and resolved turbulent kinetic energy to infer the EDR; the second is using the LMT for converting absolute vertical velocity (and its combination with the Richardson number) to EDR-scale. As a result, we found that the model-based EDRs were about 0.3–0.4 m^2/3 s⁻¹ near the CIT event, which is consistent with the estimated EDRs from both aircraft and radar observations.

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.

Based on a convective gravity wave drag parameterization scheme in a numerical weather prediction (NWP) model, previously proposed near-cloud turbulence (NCT) diagnostics for better detecting turbulence near convection are tested and evaluated by using global in situ flight data and outputs from the operational global NWP model of the Korea Meteorological Administration for one year (from December 2016 to November 2017). For comparison, 11 widely used clear air turbulence (CAT) diagnostics currently used in operational NWP-based aviation turbulence forecasting systems are separately computed. For selected cases, NCT diagnostics predict more accurately localized turbulence events over convective regions with better intensity, which is clearly distinguished from the turbulence areas diagnosed by conventional CAT diagnostics that they mostly failed to forecast with broad areas and low magnitudes. Although overall performance of NCT diagnostics for one whole year is lower than conventional CAT diagnostics due to the fact that NCT diagnostics exclusively focus on the isolated NCT events, adding the NCT diagnostics to CAT diagnostics improves the performance of aviation turbulence forecasting. Especially in the summertime, performance in terms of an area under the curve (AUC) based on probability of detection statistics is the best (AUC = 0.837 with a 4% increase, compared to conventional CAT forecasts) when the mean of all CAT and NCT diagnostics is used, while performance in terms of root-mean-square error is the best when the maximum among combined CAT and single NCT diagnostic is used. This implies that including NCT diagnostics to currently used NWP-based aviation turbulence forecasting systems should be beneficial for safety of air travel.

Turbulence in the upper troposphere and lower stratosphere (UTLS) plays an important role in total energy dissipation and in the transport and mixing of heat, momentum, and atmospheric constituents while also posing significant hazards to aviation. In this study, we leverage high‐altitude in situ observations from the NASA Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) field campaign—including data acquired near convection and at altitudes rarely covered by commercial aircraft—to investigate turbulence and its potential link to UTLS composition. We find that strong turbulence occurs frequently within 2 km above the tropopause, which corresponds to 1–2 km above deep convective cloud tops, particularly within moist convective plumes characterized by enhanced water vapor. The occurrence of strong turbulence increases with proximity to convection with elevated frequencies persisting out to 100 km from convective cores. In particular, enhanced turbulence potential occurs near UTLS convective outflows, which is supported by favorable environmental factors such as strong vertical wind shear, flow deformation, and large divergence tendencies. Furthermore, although turbulence intensity and water vapor are generally weakly correlated, positive correlations occur more frequently near the tropopause and under strong vertical wind shear, suggesting that turbulent mixing may contribute to localized stratospheric moistening under certain atmospheric conditions. The findings demonstrate the utility of high‐altitude in situ observations for advancing our understanding of UTLS turbulence and its influence on atmospheric composition, with implications not only for climate but also for future high‐altitude aviation applications.

Small‐scale turbulence above 10 km is investigated using observations from two recent airborne field campaigns: the Asian Summer Monsoon Chemical & Climate Impact Project (ACCLIP) and the Dynamics and Chemistry of the Summer Stratosphere (DCOTSS). Turbulence is enhanced by factors of 2–24 inside clouds, within 100 km of active deep convection, above atmospheric jets, and above mountains coincident with strong low‐level winds. In DCOTSS, which sampled outflow from overshooting convection over the continental United States, turbulence occurred most frequently near the tropopause, indicating enhanced troposphere‐stratosphere exchange. In ACCLIP, conducted over the northwestern Pacific, turbulence was most common in the upper troposphere. We evaluate the performance of several turbulence diagnostics computed from the European Centre for Medium‐Range Weather Forecasts' fifth reanalysis (ERA5) and operational forecasts, along with the clear‐air turbulence flag recently introduced in the forecasts. Among the diagnostics tested, TI3 computed from operational forecast data is most skillful.