Because of the rapid and continuing increase in air traffic, and perhaps impacts from global warming, there is some evidence that the number of turbulence encounters has been increasing ( Jaeger and Sprenger 2007 Wolff and Sharman 2008 Kim and Chun 2011) and are expected to continue to rise in the future (e.g., Williams and Joshi 2013 Williams 2017 Storer et al. It can be more hazardous at cruising altitudes where flight crew and passengers are likely to be unbuckled, which may lead to serious inflight injuries as well as structural damage and premature aging of the airframe and flight/service delays ( Sharman and Lane 2016).
In-flight bumpiness due to unexpected turbulence encounters can be the most stressful and inconvenient experience for people on board commercial aircraft. We expect that the new G-GTG forecasts will be beneficial to aviation users globally.Ī multidiagnostic-based en route nonconvective turbulence forecasting algorithm has been developed to provide better predictions of clear-air and mountain-wave turbulence for use in global strategic flight planning. This will be improved in the future when we use this methodology with NWP ensembles and more observation data will be available for calibration. The probabilistic G-GTG forecast is more reliable at predicting light-or-greater (EDR > 0.15)- than moderate-or-greater (EDR > 0.22)-level turbulence, although it suffers from overforecasting. Objective evaluations of the G-GTG against global in situ EDR measurement data show that both deterministic and probabilistic G-GTG significantly improve the current WAFS CAT product, mainly because the G-GTG takes into account turbulence from various sources related to CAT and MWT. In addition, a probabilistic EDR forecast is produced by the percentage agreement of the individual CAT and MWT diagnostics that exceed a certain EDR threshold for turbulence (i.e., multidiagnostic ensemble). Deterministic CAT and MWT EDR forecasts are derived from ensembles of calibrated multiple CAT and MWT diagnostics, respectively, with the final forecast provided by the gridpoint-by-gridpoint maximum of the CAT and MWT ensemble means.
The G-GTG provides an atmospheric turbulence intensity metric of energy dissipation rate (EDR) to the 1/3 power (m 2/3 s –1), which is the International Civil Aviation Organization (ICAO) standard for aircraft reporting. For the next generation of the World Area Forecast System (WAFS), the global Graphical Turbulence Guidance (G-GTG) has been developed using global numerical weather prediction (NWP) model outputs as an input to compute a set of turbulence diagnostics, identifying strong spatial gradients of meteorological variables associated with clear-air turbulence (CAT) and mountain-wave turbulence (MWT).
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