Exercise #4




  • Problem #1 - The meteorology error tutorial section showed results only using the NARR and GBLR data. Add the ERA40 and WRF27 data to the graphic.

  • Hint - Retrieve traj_fwrd_control.txt to get started.

  • Solution - Note that the first trajectory in the display list determines the image domain.

  • Problem #2 - Determine the sensitivity of the previous result to the integration time step by comparing the calculation using the default time step with an arbitrary one set to the maximum value of 60 minutes. Computational differences can be enhanced using the 3 km resolution WRF data.

  • Hint - Define the WRF03 data file and compute the trajectory (without using SETUP.CFG). Then open the advanced menu and set the time step to 60 minutes. After changing the name of the trajectory endpoints file, rerun the model.

  • Solution - Although trajectories using the smaller domain 3 km data terminate near the Ohio-Pennsylvannia border, it is already clear that the mid-boundary layer trajectories have become quite different from each other. The longer timestep (red trajectory) forces the calculation to skip over data points resulting in a smoother trajectory. Unlike other modeling approaches, Lagrangian calculations will not fail if the time step criteria is violated.