Watching the hurricane come in and I’m trying to figure out what the dBZ ranking means. The equivalent reflectivity factor goes right over my head. Thanks!
In: Planetary Science
dBZ stands for decibels of reflectivity. I know, that doesn’t help much, so:
Weather radar is used to (try to) measure the amount of precipitation (like rain, sleet, or snow) that is falling. Radar can’t directly measure rain — instead, the radar sends out a radio signal and measures how much was reflected back. Individual raindrops (or hailstones or snowflakes) will reflect a certain amount of the radio signal back to the radar. The radar measures the strength of this reflection in decibels (dB) of reflectivity (abbreviated Z) and — along with other information about the reflected signal — uses it to estimate how much rain is currently falling.
In the US, the National Oceanic and Atmospheric Administration (NOAA) has a standard scale for weather radar dBZ that is used to color code the radar images you see. This is how you get the blue and green for light rain, yellow and orange for moderate, and red to purple for really heavy rain.
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