CLIMATOLOGICAL ANALYSIS Page 3 of 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Trajectory Cluster Analysis - Example As an example, let us use the following set of 25 back-trajectories. They correspond to a subset of precipitation samples taken in 1993 at State College, PA (AIRMoN site PA15). The trajectories originate at 09 UTC at an altitude of 2000 m agl and have a duration of 36 hours. Trajectory cluster analysis identified five clusters, depicted below by the mean trajectory for each of the clusters. Each cluster represents a unique transport path and associated travel time. In this case, the clusters are all composed of five trajectories. The cluster number is arbitrary.