190-00962-02 Rev. A
Garmin G1000 Pilot’s Guide for the Diamond DA42NG
325
HAZARD AVOIDANCE
SY
STEM
O
VER
VIEW
FLIGHT
INSTRUMENTS
EIS
AUDIO P
ANEL
& CNS
FLIGHT
MANA
GEMENT
HAZARD
AV
OID
ANCE
AFCS
ADDITIONAL
FEA
TURES
APPENDICES
INDEX
No Radar Coverage
Figure 6-68 Precipitation Data Legend
Boundary of GFDS
weather data request
The display of no 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 tick-marked boundary line 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
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.