**Local Application Documentation**

**Name: radfog.pl 2.0 Radiation Fog Potential**

**Code Author(s): Anthony Petrolito**

**Code language(s): PERL/Tk**

**INTRODUCTION:**

This application calculates potential for radiation fog based on United
Parcel Service (UPS) methods (Baker et al., 2002). The user may select a
MOS station from a menu or input the forecaster overnight minimum
temperature. The user must also input a cross over temperature and soil
temperature. Output is in a table format for the period 0000 UTC to 1200
UTC. Cross over technique and modified Richardson number (Mri) are
included, along with the potential soil temperature contribution to fog
formation. Output display in red indicates a high chance of fog, yellow
a moderate chance of fog, and green suggests a low chance of fog. It is
best to combine the results from the cross over technique and Mri. There
is higher confidence in the forecast when the two methods are in
agreement. The application GUI is shown in Fig. 1.

![](media/image1.png){width="5.992361111111111in"
height="5.602777777777778in"}

**Figure 1.** Radiation Fog Potential GUI.

**INSTALLATION:**

To extract the needed files from **radfog.tar**:

Create the directory radfog. The default and recommended location is
/home/local/lclapps/:

**mkdir radfog**

Move or copy the tar file, **radfog.tar**, to the radfog directory.

Change (**cd**) to the radfog directory.

As user fxa, extract the files from **radfog.tar** by:

**tar --xvf radfog.tar**

In the radfog directory:

**mkdir data**

There should be two directories. The main directory should be radfog and
there should be one sub-directory. The two directories are listed below,
along with their function or use.

-   radfog - Contains two Perl/Tk scripts.

-   data - Contains the **config** file, and all the data files used for
    decoding.

SETUP: **configradfog.pl**

This Perl/Tk program will create the configuration file. The user will
input the required information for configuration using a GUI. The
configuration GUI is shown in Fig. 2. The various required inputs for
configuration are explained in Table 1. A sample FRH (FOUS) product
showing the sections and subsections needed for proper decoding is shown
in Fig. 3.

![](media/image2.png){width="5.992361111111111in"
height="5.914583333333334in"}

**Figure 2.** Configradfog.pl GUI.

+-----------------------+-----------------------------------------------+
| Path to config file:  | The default path to the **data**              |
|                       | sub-directory is automatically inserted and   |
|                       | recommended. This path can be changed,        |
|                       |                                               |
|                       | however the **require** statement in the main |
|                       | program                                       |
|                       |                                               |
|                       | (radfog.pl) will have to be changed as well.  |
+-----------------------+-----------------------------------------------+
| Path to store MOS and | The default path to the data sub-directory is |
| FRH                   | automatically inserted and recommended.       |
|                       | However, the user can                         |
| data files:           |                                               |
|                       | change this path.                             |
+-----------------------+-----------------------------------------------+
| Input the number of   | This input sets up the number of MOS stations |
| MOS                   | that will be                                  |
|                       |                                               |
| stations:             | included in the menu. The limit is 10         |
|                       | stations, but this                            |
|                       |                                               |
|                       | limit can be increased by adding to the       |
|                       | stations and menu                             |
|                       |                                               |
|                       | sections of the main program (radfog.pl).     |
+-----------------------+-----------------------------------------------+
| Input the MOS         | Input the MOS station identifiers that will   |
| stations:             | be included                                   |
|                       |                                               |
|                       | in the menu. Type in the 3 letter identifiers |
|                       | with a space between them. Example: CAE CUB   |
|                       | AGS...etc.                                    |
+-----------------------+-----------------------------------------------+
| Input FRH Product Key | Input the FRH Product representative of the   |
|                       | forecast area.                                |
|                       |                                               |
|                       | The product will be used for Boundary Layer   |
|                       | data needed                                   |
|                       |                                               |
|                       | for Modified Richardson Number (MRi)          |
|                       | calculations.                                 |
+-----------------------+-----------------------------------------------+
| Input FRH Section     | FRH Section numbers are identified in Fig. 3. |
| number                |                                               |
|                       | Input the FRH Section number needed for       |
|                       | decoding the                                  |
|                       |                                               |
|                       | station of choice.                            |
+-----------------------+-----------------------------------------------+
| Input FRH Subsection  | FRH Subsection numbers are identified in Fig. |
|                       | 3.                                            |
| number                |                                               |
|                       | Input the FRH Subsection number needed for    |
|                       | decoding                                      |
|                       |                                               |
|                       | the station of choice.                        |
+-----------------------+-----------------------------------------------+
| Input FRH Station id  | FRH Station id #'s are identified in Fig. 3.  |
| \# 1, 2,              | Input the FRH                                 |
|                       |                                               |
| and 3                 | Station id #'s as shown in Fig. 3 for your    |
|                       | particular FRH product. (3 letter             |
|                       | identifiers)                                  |
+-----------------------+-----------------------------------------------+

**Table 1.** Configuration Inputs.

![](media/image3.png){width="5.992361111111111in" height="5.01875in"}

**Figure 3.** FRH (FOUS) product example.

From Fig. 3, example FRH inputs for SAV (Savannah, Ga) are as follows:

Section number = 0

Subsection number = 1

Station id #1 = CAE

Station id #2 = MIA

Station id #3 = TLH

**radfog.pl 2.0**

This is the main Perl/Tk program and can be executed at the command line
or a local menu when needed. Although the configuration is set up for no
more than ten MOS Stations, only minor changes to the Stations and Menu
sections are needed to increase the number of MOS Stations. The local
version of this program has been in use since 2002 and the soil
temperature is automatically ingested into the program from the CAE
Hydro Area Temps and Precipitation product (HYDCAE). Since the format of
the HYD product is not standardized, the soil temperature subroutine was
changed to allow simple forecaster input from the GUI. The code to
decode the soil temperature from the HYD or a similar product is
included (Soil Temperature subroutine) and may be modified for local
use.

METHODOLOGY:

1\) Select a station and either MAVMOS or METMOS from the menu.

2\) Input the crossover temperature (lowest dew point during the
afternoon).

3\) Input the soil temperature.

4\) Press 'Compute'.

5\) Output is displayed.

Alternate input method:

1\) Input the forecaster overnight minimum temperature instead of using
MOS. Make sure to clear the station and MOS if previously selected. This
can be done by selecting clear from the menu.

If the program is executed during the late evening and early morning
hours (0000 UTC-

0800 UTC) a dialog box will appear giving the user the option of either
selecting output for the rest of the morning period (to 1200 UTC) or the
next night period.

**Reference**

Baker, R., J. Cramer and J. Peters, 2002: Radiation Fog: UPS Airlines
Conceptual Models and Forecast Methods. Preprint, 2002 Portland Aviation
Conference, 6 pp. \[available online at:
http://www.meted.ucar.edu/dlac/website/resources/upspaper.pdf\]