Wind gradients and their impact on trajectory prediction

Wind gradients affect the accuracy of 4D trajectories (4DT) in several ways: a) wind shear encountered by the aircraft along a climb or descent segment translate into a pseudo-force present in the inertial reference frame; b) gradients of the wind speed along the path could introduce modeling errors due to acceleration; and c) variations of the wind vector taken at the same location but different times, if not taken into account in the model could introduce prediction errors. This paper presents an analysis of the various wind gradients listed above and their effect on trajectory prediction. A sample of 90 days of wind grid data obtained from the National Centers for Environmental Prediction (NCEP) server was analyzed to compute the gradients. The operational impacts of these results are explored and statistics of the wind gradients and their associated trajectory effects are presented.