Garmin G1000 King Air C90GT - Manual (Page 315)

190-00663-01 Rev. A Garmin G1000 Pilot’s Guide for the Hawker Beechcraft C90A/GT 301
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
Displaying NEXRAD weather information:
1) Select the MAP Softkey (for the PFD Inset Map, press the INSET Softkey). This step is not necessary on the
Weather Data Link Page.
2) Select the NEXRAD Softkey.
Composite data from all the NEXRAD radar sites in the United States is shown. This data is composed of
the maximum reflectivity from the individual radar sweeps. The display of the information is color-coded to
indicate the weather severity level. All weather product legends can be viewed on the Weather Data Link Page.
For the NEXRAD legend (Figure 6-11), press the LEGEND Softkey when NEXRAD is selected for display.
No Radar Coverage
Figure 6-11 NEXRAD Data with Legend
The display of radar coverage is always active when either NEXRAD or ECHO TOPS is selected. Areas
where NEXRAD radar coverage and Echo Tops information is not currently available or is not being collected
are indicated in grayish-purple. Radar capability exists in these areas, but it is not active or is off-line.
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 back to the radar receiver (designated by the
letter Z). The value of Z increases as the returned signal strength increases.
neXraD l
imitations
NEXRAD radar images may have certain limitations:
• NEXRAD 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.