190-00728-04 Rev. A
Embraer Prodigy® Flight Deck 100 Pilot’s Guide
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HAZARD AVOIDANCE
No Radar Coverage
Figure 6-11 NEXRAD 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 gray shade of purple.
reflectivity
Reectivityistheamountoftransmitted powerreturnedtotheradarreceiver.Colors ontheNEXRAD
displayaredirectly correlative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 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 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(wethailvs.rain). 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.
•Whenzoomedintoarangeof30nm,eachsquareblockonthedisplayrepresentsanareaoffoursquare
kilometers.The intensitylevel reectedbyeach squarerepresents the
highest
levelof NEXRADdata
sampledwithinthearea(Figure6-12).
•Below52ºN, ifthetype ofprecipitationis unavailable,thesystem displaysthe precipitationusingthe
color codes associated with rain.