Comparison of Ensemble Predictions of a New Probabilistic Fast-Time Wake Vortex Model and Lidar Observed Vortex Circulation Intensities and Trajectories

Lidar observations of wake vortex circulation intensity and trajectories are compared to the predictions of a new probabilistic fast-time wake vortex model. The new probabilistic model utilizes several different deterministic fast-time vortex models and produces ensemble model predictions of wake vortex behavior. Multiple numerical predictions are conducted in the form of a Monte Carlo analysis with slightly different initial conditions that are all plausible given the past or current set of observations and measurements. The probabilistic model predictions attempt to account for the two primary sources of uncertainty in fast-time wake vortex models: the errors introduced by sensitivity to the initial aircraft parameters and environmental conditions; and errors introduced because of imperfections in the model assumptions and simplifications. There are three main findings of this study. First, the new probabilistic fast-time wake vortex prediction model reproduces observed vortex behavior and predicts approximately the same mean and spread as the observations. Second, uncertainties in the generator aircraft parameters are as important as uncertainties in the atmospheric conditions in generating estimated spread in the model predictions. And third, the spread between the different deterministic fast-time wake vortex models overlaps when plausible uncertainties in initial conditions are used. While development and validation of the new probabilistic fast-time wake vortex model is on-going, it appears that it will develop into a useful tool to help assess deterministic fast-time model performance, to assist in planning future wake vortex field observation campaigns, and eventually to examine current or proposed wake separation standards.