Garmin G1000 NXi Pilot's Manual page 275

If the system has not received all available NEXRAD weather data (such as during initial FIS-B signal
NOTE:
acquisition or in areas of marginal or poor signal reception), the system may display areas of no radar
coverage which are subsequently removed as radar data is received. It may take up to approximately ten
minutes to receive all FIS-B data, when adequate reception is available.
r
efleCTIvITy
Reflectivity is the amount of transmitted power returned to the radar receiver. Colors on the NEXRAD
display are directly correlative to the level of detected reflectivity. Reflectivity as it relates to hazardous
weather can be very complex.
The role of radar is essentially to detect moisture in the atmosphere. Simply put, certain types of weather
reflect radar better than others. The intensity of a radar reflection is not necessarily an indication of the
weather hazard level. For instance, wet hail returns a strong radar reflection, while dry hail does not. Both
wet and dry hail can be extremely hazardous.
The different NEXRAD echo intensities are measured in decibels (dB) relative to reflectivity (Z). NEXRAD
measures the radar reflectivity ratio, or the energy reflected
letter Z). The value of Z increases as the returned signal strength increases.
neXraD l
NEXRAD radar images may have certain limitations:
• At smaller map ranges, individual blocks of NEXRAD weather data are viewable. For the regional version
of the NEXRAD weather product, the smallest block represents 1.5 nm wide by 1 nm tall. For the
continental United States version of the NEXRAD weather product, each block is 7.5 nm wide by 5 nm
wide. The color of each block represents the highest radar reflectivity detected within that area.
• The continental US version of the NEXRAD weather product is not available above 60º of latitude.
The following may cause abnormalities in displayed NEXRAD radar images:
• Ground clutter
• Strobes and spurious radar data
• Sun strobes (when the radar antenna points directly at the sun)
• Interference from buildings or mountains, which may cause shadows
• Metallic dust (chaff) from military aircraft, which can cause alterations in radar scans
190-02177-00 Rev. A
IMITaTIonS
Garmin G1000 NXi Pilot's Guide for the Cessna Nav III
HAZARD AVOIDANCE
back to
the radar receiver (designated by the
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