Why use Radar Data?
What kind of data is available from the radar?
How can radar data be used to track storms?


Why use Radar Data?
Radar was developed during World War II as a way to detect enemy aircraft. Radar works by transmitting a beam of electromagnetic energy (radio waves) into the atmosphere then "listening" for some of the energy to be returned (the echo). Enemy airplanes could be detected because they reflected some of the transmitted energy. It was soon discovered that not only did airplanes reflect radio waves, but clouds and precipitation did as well. This led to the birth of radar meteorology.

When radar energy from the transmitter strikes water particles in the atmosphere some of the energy is returned. The amount of reflected energy indicates the density of the water droplets. Extremely dense droplets, like those encountered during severe weather, are easily detected by plotting an image of the intensity of the reflected radar signal. A color scale is typically used to show how much energy was returned from a radar scan. The more energy returned, the more severe the weather. In addition to the intensity of the severe weather, modern meteorological radars can also determine the speed and movement of the weather. These data can be analyzed by a computer program to gather additional information such as estimates of rainfall amounts, determination of cloud tops, and the location and movement of storms.

What kind of data is available from the radar?
RadarLabGIS allows the user to view several types of radar data:

Reflectivity
Reflectivity is used to find the location of precipitation and severe weather. The "base" reflectivity refers to a radar scan in which the radar dish is tilted just 0.5 degrees above the horizon. This is the most commonly used radar product and is what is typically seen on the local news or The Weather Channel. RadarLabGIS also provides data from additional tilts. The additional data is useful for analyzing the 3-D structure of storm cells and other weather events.

Storm Attributes
Computer analysis of the radar data may indicate the presence of storm cells. "Storm attributes" indicate the position, speed, movement, and intensity of each identified cell. Additionally, the computer analysis may indicate the presence of a tornado signature or a mesoscale rotation. RadarLabGIS allows you to view the storm attributes and plot them on a map in a graphical form.

Radial Velocity
This dataset portrays the speed of the radar echoes with respect to the radar site. This product is often used by meteorologists to find rotation in a weather event.

Precipitation Totals
RadarLabGIS provides three types of precipitation totals: the "1 Hour" precipitation total, the "3-Hour" precipitation total, and the "Storm" precipitation total. The 1-Hour and 3-Hour totals indicate the estimated amount of rainfall for the past one hour and three hours respectively. The "Storm" precipitation total indicates the amount of rainfall associated with the entire weather event. Technically speaking, it begins accumulating when the radar switches from clear-air to precipitation mode.

Echo Tops
This product shows the estimated tops of clouds.

VIL
This product shows the amount of vertically integrated liquid water in the atmosphere. High VIL values are a good indicator of severe weather. Extremely high values are usually associated with hail.

VAD Wind Profile
This product shows the wind speed at various elevations within the atmosphere.

How can radar data be used to track storms?
RadarLabGIS can create "storm tracks," or graphical depictions of the storm attributes produced by analysis of the radar data (this analysis is done at the radar site itself). A storm track marks the current location of the storm cell (the centroid) and draws a line indicating the future movement of the cell based on its current speed and direction. Markers along the line mark the future location of the cell after 15, 30, 45, and 60 minutes.

For more information, e-mail us or call 800-337-5263.