Garmin GXM 40 - Manual (Page 37)

GXM 40 Owner’s Manual 
Appendix
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 represented by the dBZ values listed
in the dBZ Values/Precipitation Table.
Display
Rain
Display
Snow
dBZ
Rain
(inches per
hour)
Snow
(inches per
hour)
Remarks
Rain Snow
≤ -10 0.00 in. 0.00 in.
-5 0.00 in. trace
0 0.00 in. trace–0.05 in. Very Light
5 0.00 in. trace–0.10 in. Light
10 0.00 in.–trace 0.01 in. Light Light
15 0.01 in. 0.1–0.2 in. Light Light
20 0.02 in. 0.2–0.3 in. Light Light
25 0.05 in. 0.3–0.5 in. Light Light–Moderate
30 0.09 in. 0.5–0.7 in. Light–Moderate Moderate
35 0.24 in. 0.7–1.0 in. Moderate Heavy
40 0.48 in. 1 in.+ or sleet Heavy Heavy
45 1.25 in. 1 in.+ or sleet Heavy Heavy
50 2.5 in. sleet Intense
55 5.7 in. sleet Extreme
55+ 12.7 in. Extreme
dBZ Values/Precipitation Table