Pilot's Guide

190-00552-05 Rev. A
Garmin G1000 Pilot’s Guide for the Corvalis/Corvalis TT
SYSTEM
OVERVIEW
FLIGHT
INSTRUMENTS
EIS
AUDIO PANEL
& CNS
FLIGHT
MANAGEMENT
HAZARD
AVOIDANCE
AFCS
ADDITIONAL
FEATURES
APPENDICES INDEX
295
HAZARD AVOIDANCE
Figure 6-11 NEXRAD Data with Legend and Areas
with No Radar Coverage
No Radar
Coverage
Thedisplayofno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 a gray shade of purple.
reFlectivity
Reectivityistheamountoftransmittedpowerreturnedtotheradarreceiver.ColorsontheNEXRAD
displaydirectlycorrelatetothelevelofdetectedreectivity.Reectivity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
reectradarbetterthanothers.Theintensityofaradarreectionisnotnecessarilyanindicationofthe
weatherhazardlevel.Forinstance,wethailreturnsastrongradarreection,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reectivity(Z).NEXRAD
measurestheradarreectivityratio,ortheenergyreectedbacktotheradarreceiver(designatedbythe
letterZ).ThevalueofZincreasesasthereturnedsignalstrengthincreases.
neXraD limitations
NEXRADradarimagesmayhavecertainlimitations:
•NEXRADbasereectivitydoesnotprovidesufcientinformationtodeterminecloudlayersorprecipitation
characteristics.Forexample,itisnotpossibletodistinguishbetweenwetsnow,wethail,andrain.
•NEXRADbasereectivityissampledattheminimumantennaelevationangle.AnindividualNEXRAD
sitecannotdepicthighaltitudestormsatcloseranges.Ithasnoinformationaboutstormsdirectlyover
the site.