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NEXRAD Intensity
Colors are used to identify the different NEXRAD
echo intensities (reflectivity) measured in dBZ (deci-
bels of Z). "Reflectivity" is the amount of transmitted
power returned to the radar receiver. Reflectivity
(designated by the letter Z) covers a wide range of
signals (from very weak to very strong). So, a more
convenient number for calculations and comparison, a
decibel (or logarithmic) scale (dBZ), is used. The dBZ
values increase as the strength of the signal returned
to the radar increases. There are seven gradations for
rain, two gradations for mixed rain and snow, and two
gradations for snow.
To display the NEXRAD Intensity Legend:
1.
While viewing the XM Weather page, press the
MENU key to display the Page Menu.
2.
Turn the large or small knob to select "Display
legend?"
3.
Press ENT to display the NEXRAD Intensity
Legend.
All manuals and user guides at all-guides.com
190-00356-30 Rev H
4.
Turn the large or small knob to scroll through
the full table. Press CLR to return to the normal
view.
NEXRAD Abnormalities
There are possible abnormalities regarding dis-
played NEXRAD images. Some, but not all, causes of
abnormal displayed information include:
• Ground Clutter
• Strobes and spurious radar data
• Sun strobes, when the radar antenna points
directly at the sun
• Military aircraft deploy metallic dust which can
cause alterations in radar scans
• Interference from buildings or mountains,
which may cause shadows
• Scheduled maintenance may put a radar off-line
Part Two: Section 2
XM Weather
15
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