The TVAMet software application provides means to view real-world and simulated fifteen-minute and hourly meteorological data averages provided by the Nuclear Power Group (NPG) of the Tennessee Valley Authority (TVA). This dataset is available to all users, internal and external to TVA, who possess a valid TVA Network ID (NTID). This interface was designed specifically to provide the aforementioned data to the Emergency Management Agencies of the states of Tennessee and Alabama.
This software in limited in scope to use by authenticated NTID holders. A web browser must be used to access this software.
Authorized users are free to use the data presented on TVAMet as needed. However, real-time data collected on the TVA towers is PROPRIETARY and should not be released to the general public in a raw, unverified form. The data are collected specifically to support TVA Emergency Preparedness activities, and the general public may not properly interpret the information during an emergency. TVA will provide the data to any requester after it has been validated.
The meteorological data interface is composed of four pages per operating site:
- 15 Minute Meteorological Data
- Hourly Meteorological Data
- 15 Minute Simulated Meteorological Data
- Hourly Simulated Meteorological Data
These pages can be found by navigating to an operating site's portal page by clicking that site's name on the home page or on the navigation bar. Data are available on a rolling 168-hour (7 day) window.
The meteorological data pages provide the user with the options to:
- Specify the number of hours of data to show ("Show past XX hours" input). This option allows the user to view any subset of data between 1 and 168 hours into the past.
- Turn automatic data refresh on ("Refresh On" button) or off ("Refresh Off" button). This option, if enabled, automatically reloads the meteorological data every fifteen minutes on the quarter hour.
- Print the current data view ("Print" button). This option allows the user to generate a printer-friendly version of the data currently being viewed.
Meteorological data are presented in the local prevailing time zone; Browns Ferry data are in Central time, while Sequoyah and Watts Bar data are in Eastern time.
3.1.1 Description of Meteorological Data Points
Meteorological sensor outputs (except rainfall) are measured every five seconds (720 per hour). Rainfall is measured continuously as it occurs.
With the exception of rainfall, data are averages ending at the time listed (15-minute or hourly). Rainfall is the total for the time period.
The data logger accumulates output and performs data calculations to generate the following for display on the website:
- Vector Wind Direction is the vector sum of all wind directions during the period (180/15 minutes, 720/hour) weighted by the associated wind speed.
- Vector Wind Speed is the length of the wind direction vector divided by the number of observations.
- Average Wind Speed is the arithmetic average of the individual wind speed observations during the period (regardless of wind direction).
A comparison between Vector and Average Wind speeds provides an indication of how steady the wind is blowing. Values close together indicate there is little variability in wind direction, while much lower vector values indicate more variability.
- Horizontal WD Sigma Theta is the standard deviation of wind directions (regardless of wind speed).
The magnitude of Sigma Theta indicates the variability of the wind direction. A small value (25° or less) indicates a generally steady wind direction. A larger value indicates the wind direction is fluctuating.
- Air Temperature is the arithmetic average of the individual air temperature observations during the period.
- Lapse Rate/Stability Class indicates the vertical stability characteristics. It is calculated by subtracting the lower elevation temperature from the higher elevation temperature and adjusting to a 100m layer. Stability class is determined based on the following table:
- Rainfall is the amount of precipitation recorded during the period (15 minutes or hourly).
- Dewpoint is the arithmetic average of the individual dewpoint observations during the hour.
- Solar Radiation is the arithmetic average of the individual dewpoint observations during the hour.
Solar Radiation for a clear sky ranges from 0.00 langleys/minute (ly/min) at night to maximums near 0.80 y/min during the winter, and 1.50 y/min during the summer.
[1 ly/min = 698 watts/m2]
Each operating site's portal page contains a "Tower Information" table detailing meteorological tower constants. These constants include the tower's physical geographic location and elevation, as well as sensor heights on the tower.
3.3.1 Signing In
A user that is not currently signed in to TVAMet will be automatically taken to the sign in page upon attempting to view any TVAMet page. To sign in to TVAMet, the user must:
- Possess an active and valid TVA NTID.
- Provide his or her TVA NTID in the "NTID" blank.
- Provide his or her NT password in the password blank (denoted by a lock icon).
3.3.2 Signing Out
To sign out of TVAMet, the user simply needs to click the Sign Out button in the top right corner of any TVAMet page.
In the event of an error, the user will be informed there was an error and that an error report has been logged by the system. No user response is required.
Support for TVAMet is available by contacting TVA NPG Emergency Preparedness.
In the event of an error, the user will be informed there was an error and that will be logged by the system. No user-initiated error reporting is required.
TVA NPG Emergency Preparedness should be notified of any errors found within TVAMet related documentation.