Garmin G1000H Pilot's Manual page 334

HAZARD AVOIDANCE
The display of radar coverage is enabled 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 with white tick marks depicts the selected coverage area of the GFDS weather data
request. This boundary 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
letter Z). The value of Z increases as the returned signal strength increases.
P l
ReciPitatiOn
Radar images may have certain limitations:
• Radar base reflectivity does not provide sufficient information to determine cloud layers or precipitation
characteristics (wet hail vs. rain). For example, it is not possible to distinguish between wet snow, wet
hail, and rain.
• Radar base reflectivity is sampled at the minimum antenna elevation angle. An individual radar site
cannot depict high altitude storms at close ranges. It has no information about storms directly over the
site.
• When zoomed in to a range of 30 nm, each square block on the display represents an area of four square
kilometers.
322
Figure 6-57 Precipitation Data Legend
imitatiOns
Garmin G1000H
™
No Radar Coverage
Boundary of GFDS
weather data request
back to
Pilot's Guide for the Bell 407GX
the radar receiver (designated by the
190-01255-00 Rev. A