Help for java ACARS Display

HELP FOR THE MAP (the main page)

Detailed video tutorials are available at

HELP FOR SOUNDINGS (the soundings window)

Once you have clicked on the map to generate a sounding, it will appear in the sounding window. Sounding points further than 100 nm from the airport are coded in gray. The sounding consists of a Skew-T plot, a hodograph or flight track map, and a wind speed plot. The following thermodynamic indices are also shown, if available: A parcel may be specified by clicking with the mouse at any point. The parcel will ascend from that point (using the environmental dewpoint at that pressure), and regions of CAPE and CIn will be indicated. The Lifted Condensation Level (cloud base) for the parcel is indicated by a short horizontal black line on the parcel trajectory. Right-clicking with the mouse will bring up a selection window that will allow you to select the initial parcel dewpoint, temperature, and pressure. Click on a sounding's button to remove the parcel trajectory. Thanks to Tom Whittaker of the University of Wisconsin for providing the core of the code that performs this task.

(Against Tom's advice, and to facilitate stability calculations using ACARS soundings that often lack humidity data, iCAPE and iCIn are calculated using the temperature difference between the parcel and the sounding, rather than the virtual temperature difference. According to Doswell and Rasumssen (1994, Weather and Forecasting, 9, pp 625-629), this may cause errors > 30% for values of CAPE below 500 J/Kg and similar errors in CIn, but smaller error for larger values.)

The hodograph shows wind speed in kts, and height in km. For aircraft soundings, the hodograph window optionally shows the bearing and range from the airport to the aircraft. A "Toggle button" in the hodograph window switches between the two.

The sounding has two default altitude ranges, one extending up to 150 mb and the other to 10 mb. Each of these ranges can be zoomed by dragging the mouse diagonally across the portion of the Skew-T plot desired. Unzoom by clicking a 'scale' button. (To drag, hold the mouse button down while moving the mouse. When you release the mouse button, the zoomed region will fill the plot.) (The zoomed region will have the same aspect ratio as the main plot, so the red rectangle that appears may not follow the mouse quite the way you think it should.)

Some aircraft, because of hardware limitations, report altitude as barometrically-adjusted below 17,000 ft (the AMDAR standard is to always report altitude with respect to a standard atmosphere). For these aircraft, we use barometric-altitude if standard pressure altitude is not available. On sounding plots, the temperature trace is shown in brown is the altitude reported was barometrically adujsted.

Other functions are as follows:

Move the mouse along the sounding to see the following printed at the level of the mouse point (from left to right):

In addition, the temperature and pressure for the cursor point is indicated below the cursor.

Click on the Load Other Soundings button to pop up the choose sounding window. In this window you can

Once a sounding is loaded, you can use its button to (re)display it.

The sounding information shown on each button consists of the site name, and a code:


Unfortunately, java doesn't have convenient printing capabilities, so you will have to use a screen capture program, or cut-and-paste, to capture and print windows showing graphical data. In Microsoft Windows, you can use alt+prtscn to capture the browser window, then use ctrl+v to paste the image into MS paint or some graphics manipulation package. You can crop the imaage by drawing a box around the area of interest, then select, copy, and paste the cropped region into, for instance, powerpoint or word. We have also had good experiences with HyperSnap-Dx, a shareware program from Hyperionics.

In Unix, a shareware program called XView does the job.

For java windows that show textual data, you can copy the data in the usual way and paste it into another program for printing, e-mailing, or other processing.

Known bugs, or "issues"

Detailed help

Solid lines connect data points that can probably make useful soundings. Lines are shown if:

Data points taken within the last 20 min (with respect to the latest time loaded) are plotted at twice the size of other points (unless barbs are being displayed).

Buttons on the map window:

Several of the buttons reveal other windows. These windows can be closed in the normal way, or by clicking the button again.

(If a button is indented, it means its corresponding window is displayed, but it may be covered by other windows. To bring a window to the front, click the indented button twice.)

Other information

Please send comments or suggestions to Bill Moninger at If you're reporting a problem, please indicate what browser (with version number), operating system, and hardware you are running on. Also, it would be helpful if you could open your browser's 'java console' and send me the last several lines.

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Prepared by Bill Moninger,
Last modified: Tue Nov 17 17:26:16 GMT 2009