Valparaiso University Doppler Radar current reflectivity
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The VU Doppler Radar is an educational and research
tool. Images may not be current.
Doppler Radar reflectivity
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.
Other Radar Imagery By Server:
National Weather Service (weather.gov) Radar Page
Application Lab (RAP) Radar Page
of DuPage Satellite and Radar Page
Intellicast Radar Page
Last updated March 4, 2008 by Teresa