Garmin aera 560 Pilot's Guide - Page 93

Overview GPS Navigation Flight Planning Hazard Avoidance Additional Features Hazard Avoidance NEXRAD Abnormalities There are possible abnormalities regarding displayed NEXRAD images. Some, but not all, of those include: • Ground clutter • Strobes and spurious radar data • Sun strobes, when the radar antenna points directly at the sun • Military aircraft deploy metallic dust (chaff) which can cause alterations in radar scans • Interference from buildings or mountains, which may cause shadows NEXRAD Limitations Certain limitations exist regarding the NEXRAD radar displays. Some, but not all, are listed for the user's awareness: • NEXRAD base reflectivity does not provide sufficient information to determine cloud layers or precipitation characteristics (hail vs. rain). For example, it is not possible to distinguish between wet snow, wet hail, and rain. • NEXRAD base reflectivity is sampled at the minimum antenna elevation angle. An individual NEXRAD site cannot depict high altitude storms at close ranges, and has no information about storms directly over the site. • Radar coverage only extends to 55°N. • Any precipitation displayed between 52°N and 55°N is unknown. NEXRAD Intensity Colors are used to identify the different NEXRAD echo intensities (reflectivity) measured in dBZ (decibels of Z). "Reflectivity" (designated by the letter Z) is the amount of transmitted power returned to the radar receiver. The dBZ values increase as returned signal strength increases. Precipitation intensity is displayed using colors corresponding to the dBZ values. Appendices Index 190-01117-02 Rev. A Garmin aera 500 Series Pilot's Guide 81