13-HYSPLIT Trajectory Model Exercise

  1. Open browser and access the following site:

Under the “HYSPLIT-WEB (Internet-based)” option, select “Run HYSPLIT Trajectory Model”

  1. You will have the option to either Compute Forecast Trajectories, or to Compute Archived Trajectories. Select the archived trajectories.

  1. Use the default setting

Number of Trajectory Starting Locations / 1
Type of Trajectory / Normal

Click the “Next” button

4. On the next screen, enter the following information:

Meteorological Data / EDAS 40km (U.S., 2004-present)
Latitude & Longitude / 33.447867, -117.088649

Then click “Continue.

  1. Copy and paste your lat/long coordinates into Google Maps ( to be sure that you have entered the values correctly. For this exercise, the coordinates should correspond to one of the Pechanga air quality monitoring stations.

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  1. Under “Select the EDAS40 File”, select “edas.may12.001”

NOTE: EDAS 40km and EDAS 80km meteorological data appear in a unique format (ex: edas.may12.002). This format simply indicates the month (May), the year (12 or 2012), and the first of second half of the month (001 for the first half of the month, 002 for the second half of the month).

Click the “Next” button

  1. Enter the following values into the corresponding fields:

Trajectory direction / Backward
Vertical motiona / Model vertical velocity
Start time (UTC)b / Change hour to 7 (represents 0700)
Total run time (hours) / 24
Start a new trajectory every / 4
Maximum number of trajectories / 6
Start 1 latitude / 33.456293 (default)
Start 1 longitude / -117.105675 (default)
Level 1 heightc / 500 (default)
Plot resolution (dpi) / 96 (default)
Zoom factor / 70 (default)
Plot projection / Default
Vertical plot height units / Meters AGL
Label interval / 6 hours (default)
Plot color trajectories? / Yes (default)
Plot source location symbols? / Yes (default)
Distance circle overlay / None (default)
U.S. county borders? / No (default)
GIS ouput? / None (default)
Postscript file? / Yes
PDF file? / Yes
Plot meteorological field along trajectory? / No
Dump meteorological data along trajectory? / (default)

a) Vertical Motion (can select between):

Model Vertical velocity – describes the influence of the velocity in displacing the projectile vertically

Isobaric – thermodynamic process in which the pressure stays constant

Isentropic – assumes that the process takes place from initiation to completion without an increase or decrease in the entropy of the system < entropy is assumed to be constant >

b) Start time (UTC): Enter year, month, day, hour

Because this is a backward trajectory, we need to consider thearrival time of the parcels.

Note! When converting from GMT (Greenwich mean time) to UTC (Coordinated universal time), use conversion tool. For more information, please see NOAA’s website on UTC versus GCM (

c) Height: AGL is above ground level, and AMSL is above mean sea level

Finally, click the “Request Trajectory” button

RESULTS:

Based on your earlier selections, HYSPLIT will have three trajectory file results: GIF Plots, PostScript Plots, and PDF Plots. Additionally, there will be a “Trajectory endpoints file”.

There is also an option to modify the scenario – see, “Modify this scenario and rerun the model.” This option is very useful when running multiple similar trajectory analyses.

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If you have finished this exercise, please feel free to modify the scenario to review other options (ex: forward trajectory, different run time, number of new trajectories, etc.).

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