Valparaiso University Doppler Radar current reflectivity image. Use your browser refresh button to update the image. Caution! The VU Doppler Radar is an educational and research tool. Images may not be current.
The reflectivity image is a result of energy from the radar reflecting off of hydrometeors, such as cloud drops, rain drops, hail, and snow. Sometimes dust, insects, birds, airplanes, and buildings reflect the energy back to the radar. Reflectivity is measured in dBZ, or decibels of the radar reflectivity factor. The radar is in effect "listening" for the return of energy. The radar spends a vast majority of the time listening. Higher dBZ values indicate more intense precipitation or larger objects. Hail stones will have a large value of dBZ because of their large size. Melting snowflakes also tend to have a large value as the ice changes phase into water.
Radar data are typically collected in a volume. The radar rotates 360° at a constant elevation angle, then moves up to a new elevation angle and rotates 360°, and so on. Once it finishes the highest elevation angle, it drops down and starts the process over. Depending on how fast the radar is rotating and how many elevation steps it takes, each volume can take from 7-12 minutes. We are showing the lowest elevation angle of 0.5° (or 0.49°) because it provides a broad view of precipitation. Keep in mind that the Earth is curving below the radar beam, so the larger the distance from the radar, the higher up in the air the precipitation at 0.5° is occurring. Higher elevation angles tell us more about where snow is melting into rain, how high a storm reaches into the atmosphere, and how the vertical structure of the storm is arranged.
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