Notice the color on each scale remains the same in both operational modes, only the values change.The value of the d BZ depends upon the mode the radar is in at the time the image was created.The scale of d BZ values is also related to the intensity of rainfall.

The colors are the different echo intensities (reflectivity) measured in d BZ (decibels of Z) during each elevation scan.

"Reflectivity" is the amount of transmitted power returned to the radar receiver.

Reflectivity (designated by the letter Z) covers a wide range of signals (from very weak to very strong).

So, a more convenient number for calculations and comparison, a decibel (or logarithmic) scale (d BZ), is used.

S., forecasters use a set of rainrates which are associated to the d BZ values.

These values are estimates of the rainfall per hour, updated each volume scan, with rainfall accumulated over time.

Hail is a good reflector of energy and will return very high d BZ values.

The d BZ values increase as the strength of the signal returned to the radar increases.

Each reflectivity image you see includes one of two color scales.

One scale (far left) represents d BZ values when the radar is in clear air mode (d BZ values from -28 to +28).

The other scale (near left) represents d BZ values when the radar is in precipitation mode (d BZ values from 5 to 75).