190-00709-04 Rev. A
Garmin G1000 Pilot’s Guide for the Socata TBM 850
359
HAZARD AVOIDANCE
No Radar Coverage
Figure 6-68 Precipitation Data Legend
Boundary of weather
data request
The display of radar coverage is enabled active when Precipitation is selected for display. Areas where
precipitation radar coverage is not currently available or is not being collected are indicated in gray shade
of purple. A white boundary line depicting the selected coverage area of the GFDS weather data request
encloses the precipitation data when this weather product is displayed.
R
eFlectivity
Reflectivity is the amount of transmitted power returned to the radar receiver. Colors on the Precipitation
display directly correlate 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 radar echo intensities are measured in decibels (dB) relative to reflectivity (Z). Weather
radars measure the reflectivity ratio, or the energy reflected
back to
the radar receiver (designated by the
letter Z). The value of Z increases as the returned signal strength increases.
P
ReciPitatiOn
l
imitatiOns
Radar images may have certain limitations:
• Radar composite reflectivity does not provide sufficient information to determine precipitation
characteristics (wet hail vs. rain). For example, it is not possible to distinguish between wet snow, wet
hail, and rain.
• The radar beam may overshoot precipitation occurring below the lowest antenna beam tilt angle (0.5°),
causing no precipitation to be displayed. An individual radar site cannot depict high altitude storms at
close ranges. It has no information about storms directly over the radar site.
• When zoomed in to a range of 30 nm, each square block on the display represents an area of four square
kilometers.
Summary of Contents for SOCATA TBM850
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