Example 7 Meteorological Analysis along a Trajectory

11

Example 7Example 7Meteorological Analysis along a TrajectoryMeteorological Analysis along a Trajectory

• Configure a trajectory run to plot the model terrain height along the trajectory path.• Change the vertical motion method from “Model Vertical Velocity” to Isentropic to view differences.

22

Run a forward trajectory with NAMF12 Run a forward trajectory with NAMF12 forecast data from the Workshop archive.forecast data from the Workshop archive.

33

Choose Source LocationChoose Source Location

Enter a starting location at: 39.92N and 105.12W

44

Total run time: 84 hours

Starting height: 1500 m AGL

Model Runtime Options

55

Vertical plot height units: Pressure

Check Terrain Height to plot along trajectory. Note: this will not plot the terrain heights, but will calculate them.

Display Options

66

Submit the job and view the resultsSubmit the job and view the results

77

The resulting trajectory proceeds to the southeast into central Texas, descending from 700 hPa to nearly 950 hPa. Now click on “Modify the trajectory plot without rerunning the model” from the results page.

88

Vertical plot height units: Above model ground level

Click “Request plot.”

99

Submit the graphics job and view the resultsSubmit the graphics job and view the results

1010

The same trajectory is plotted, and since the terrain height along the trajectory was already saved, it is plotted below the trajectory (this can also be done by rerunning the model and clicking Yes to plot the meteorological data along the trajectory).

The trajectory actually follows the terrain for the most part, so care must be exercised when interpreting the up or down movement of trajectories wrt terrain.

The terrian heights (MAGL) along the trajectory can be viewed as the right-most column of the trajectory endpoints file.

1111

Use the option to rerun the jobUse the option to rerun the job

A recently added option, allows a user to rerun a model case from the results page without having to re-enter all the inputs previously entered.

Click on “Rerun the model with user entered defaults” from the results page.

Uncheck Terrain Height and check Mixed Layer Depth.

Check “Plot meteorological field along trajectory.”

1212

Submit the job and view the resultsSubmit the job and view the results

1313

This plot shows the mixed layer depth along the trajectory varied from 250 m to 687 m. (The HYSPLIT trajectory model sets the minimum mixing height to 250 m.)

1414

Review Vertical Motion Options discussion before proceeding….

1515

Use the option to rerun the jobUse the option to rerun the job

Now we will rerun the model using the Isentropic vertical motion option to demonstrate the differences observed between model vertical motion and Isentropic motion.

Vertical plot height units: Theta

Also, Uncheck “Plot meteorological field along trajectory” and uncheck “Mixed Layer Depth.”

Click on “Rerun the model with user entered defaults” from the results page.

Vertical Motion: Isentropic

1616

Submit the job and view the resultsSubmit the job and view the results

1717

Shown below left is the trajectory from Example 7 using the NAM 12 km vertical velocity fields.  To the right is the same trajectory computed using the isentropic flow assumption and choosing the Theta vertical coordinate option. This graphic shows that the potential temperature varied by only about 1 degree, however by assuming adiabatic flow conditions the second trajectory ended in northeastern Louisiana after 84 hours instead of north central Texas. The validity of the adiabatic flow assumption would need to be assessed for this case (no precipitation, cloud, etc).

IsentropicModel Vertical Velocity