Using Trajectory Analysis - Research



Using Trajectory Analysis.exe:

Analysis and Plotting of Trajectories Generated with

HYSPLIT Batch Generator

Version 1.0 (last updated December 18, 2006)

Prepared by Will Hafner

University of Washington – Bothell

whafner@uwb.edu

About the Program:

Trajectory Analysis uses the output from HYSPLIT Batch Generator to identify trajectories in a given folder, approximate the source regions of the trajectories, and prepare an output for plotting trajectories in ArcGIS 9.x. The text output of this program is formatted to plot trajectory hourly points as a point feature class or raster in ArcGIS 9.0. This guide will show the steps necessary to plot your trajectories, but for a better introduction to ArcGIS go to Ormsby et al., 2004.

This program and code are freely available from me through the University of Washington-Bothell. I welcome any comments and will provide help whenever possible. Any suggestions for improvement will be incorporated into later versions of the program. Feel free to make changes to the code to suit your own modeling purposes. However, if you do make changes to the original code, I am released from providing help if the program ceases to function.

Listed below are the current features of Trajectory Analysis, Version 1.0, plus one known problem.

Features include:

• Quick identification of the input parameters that were used in making the trajectories with HYSPLIT Batch Generator.

• Determination of the approximate source regions of the trajectories using a box approach (how often trajectories come from a given box). The altitude distribution of the hourly points within this box is also given.

• Comma delimited output of the results from the box approach.

• Comma delimited output of the hourly points for any number of selected trajectories. Output parameters include: latitude, longitude, altitude, hour, rain, potential temperature, ambient temperature, relative humidity, mixing height, and pressure. This output file is used by ArcGIS to plot the trajectories.

• ASCII outputs of: the number of hourly points in each 1° x 1° cell covering the Northern Hemisphere, the amount of precipitation from selected trajectories in each 1° x 1° cell, and the percent of hourly points in each 1° x 1° cell that are under the HYSPLIT calculated mixing height. These output files are used by ArcGIS to produce raster plots of the trajectories.

Known Problems:

• This program was written to work only with the trajectory text files generated with HYSPLIT Ver4.8. The character spacing is different in previous versions of HYSPLIT. Either download Ver4.8, or adjust the locations of latitude, longitude, etc… in the code to align with your text files output.

Prior to Running the Program:

• This program was written to work with trajectories created using my HYSPLIT Batch Generator. Learn how to use that program by reading “How to Create Trajectories Using the Visual HYSPLIT Batch Generator”

• If you wish to plot the trajectories, have access to ArcGIS 9.x.

• If you only plan on running the executable version of the Trajectory Generator program, download the newest (Version 3.0) framework from:



• If you would like to modify the code of HYSPLIT Batch Generator, you must have Microsoft Visual 2003 or newer.

Running the Program:

I have worked to make this program as user-friendly as possible, but the layout of the user interface and options available may cause some confusion. In this document, I will present examples for analyzing and plotting the 144 trajectories that were created in the example from the HYSPLIT Batch Generator Instructions. As with those instructions, italics indicate field values for our example analysis.

In the following example, we will plot trajectories in ArcGIS. The shapefile (global country outline in this case) necessary to display 10-day trajectories is provided. I have already projected this shapefile to the desired coordinate system. When you make your own trajectories, you may want different shapefiles or layers in the background. I have all of the common political boundaries (U.S., Europe, and world countries) as well as global population. Other files can be found free online. You are responsible for choosing your projections. The book ArcGIS 9: Understanding Map Projections, 2004, offers an overview of common projections plus their common uses.

To run the compiled program, open Trajectory Analysis.exe. To run the program from code in Visual , press the start button (►) in the task bar. Once open, the program should look like Figure 1 (except most of the text fields will be blank).

Opening Files and Box Analysis:

With every batch of trajectories generated, HYSPLIT Batch Generator creates a text file with a .traj extension. This file is named after the site code, end year, end month, and end day. It contains all the input parameters and the names of all the trajectories.

[pic]

Figure 1: The graphic user interface for Trajectory Analysis.

1. Click on Open File and browse for the folder where the desired batch of trajectories is stored. Select the .traj file in that folder. For our example, that file is called MBO20040425.traj.

2. Click Open in the dialog box. The input parameters for this batch of trajectories are listed on the top of the form (example: -240 hours trajectories for MBO on 4/5/2004). All of the trajectory names are listed in the scrolling list box.

3. Click Asia, California, or Alaska as the potential source region (or enter your own coordinates). For our example, use the Asian box. To determine whether your back trajectories have spent any time within this area, click the Are Trajectories in this Box? button. Depending on the number of trajectories, this may take some time. When done, note the additional columns that have appeared (see Figure 1). The “Total” column on the right side of the list box represents the number of hourly points from the trajectory that are within the box coordinates. In Figure 1 (our example), the first trajectory listed spent 9 of its 240 hours in the Asian box. The ................
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