Trajectory / Special Simulations / Run Cluster Analysis

The Trajectory Cluster Analysis window has the series of tasks necessary for running a trajectory cluster analysis. This differs from most, if not all, other HYSPLIT GUI windows that only run one program or do one task. Given a set of trajectories beginning at one location, the cluster analysis will objectively result in sub-sets of trajectories, called clusters, that are each different from the other sub-sets. The program will usually produce at least one possible outcome set of clusters. If more than one outcome is given, the user must then subjectively choose one for the final result.

Step 1. Inputs.

Step 2. Run Cluster Program. Possible solutions to the cluster analysis are available at the end of this step.

The cluster process is as follows: Initially, each trajectory is defined to be a cluster. There are N trajectories and N clusters. The cluster process is an iterative process consisting of N-1 passes through all the clusters. In the 1st pass, the two closest clusters (trajectories) are paired, resulting in N-1 clusters. Similarly in the 2nd pass, the two closest clusters are paired, resulting in N-2 clusters. In this case, either the cluster having two trajectories could be paired with another trajectory or two clusters, each with one trajectory, could be paired. This process continues until all trajectories are in 1 cluster. The cluster program produces six output files:

On a typical PC, a cluster run with 365 trajectories, 36-h duration, and using every hourly endpoint, will take a couple minutes. Going beyond several years of trajectories will result in a run that will take a long time and/or use much memory. A warning message is given for larger runs, but there is no simple way to identify how large a cluster job is possible.

Step 3 Get Results. This step may be repeated using different numbers of clusters. If you exit the GUI, but have not archived your results, enter the Run_ID and the Archive parent folder again from Step 1, then continue with Step 3. If you have already archived the results, but want to try a different number of clusters, manually copy everything from the archive directory to /hysplit/working, then enter the number of clusters, etc.



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