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The display of the echo intensity
Two modes: Clear Air & Precipitation Mode
The most common base tilt angle is 0.5°
Shows reflectivity closest to the ground
It is possible for hail to be seen when reflectivity values reach 60 dBZ (see image below).
Image Description: Radar Products - Reflectivity
Radar image for Grand Rapids, Michigan (KGRR). Shows a system returning reflectivity values measuring blue, green, then yellow. These colors are associated with values in the color bar to the right. In DBZ, blues range from 5 - 20; greens range from 20 -35; and yellows range from 35 - 45.
Image Description: How a Doppler radar works - Reflectivity
On the left-hand side, the Doppler radar sends out a beam through the two clouds. In the first cloud on the left-hand side, the beam is lower in the cloud. While in the second, farthest cloud, the beam scans the top portion of the cloud.
Near the radar, the beam is lower to the ground and "sees" low in the storms. As distance increases, the beam's altitude also increases and can overshoot the core of heavier precipitation.
Clear Air Mode
Clear Air Mode
Most sensitive mode
The radar operates in this mode 95% of the time (depending on location)
Detects boundaries or smaller objects like dust, birds, wind turbines, etc.
Can also be used to detect light snow
Image Description: Clear Air Mode
Clear air mode of a radar over central Illinois. The yellow returns are from insects and turbulence. The red returns are from ground clutter.
Precipitation Mode
Precipitation Mode
Used when precipitation is occurring or is expected in the forecast area
Stratiform precipitation is shown here to the right, in greens and blues.
Precipitation cells (convective precipitation) in yellows, oranges, and reds.
Image Description: Precipitation Mode
The blues and greens in the top right of the image represent stratiform precipitation.
The yellows, oranges, and reds in the middle of the image represent convective precipitation.
Convective vs. Stratiform Precipitation
Convective vs. Stratiform Precipitation
Convective precipitation has limited aerial coverage
Showers and thunderstorms
The precipitation is more localized
Stratiform precipitation is a more uniform event
All day steady rain
More widespread & even distribution
Image Description: Convective Vs. Stratiform Precipitation
Convective precipitation is seen in the top left of the image with the reds, yellows, and oranges.
Stratiform precipitation is seen on the right-hand side of the image with the greens and blues.
Note the heavier precipitation in a "bullseye" in MN
Surrounding area in green is more widespread and evenly distributed
Image Description: Identifying Stratiform and Convective Precipitation
Image of the NDAWN network, with precipitation totals from June 25th, 2022.
Convective precipitation is located in the area with the 5.22 inches of rain. Shown as the "bullseye" red center to the east.
Stratiform precipitation is located in the green area surrounding the "bullseye".
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