Question Regarding Negative Reflectivity (dBZ) Values in Contour Plot Scale

[ADgit7]

Hi,

I have created a few charts and seen a few examples of making colour contour plots of reflectivity (dBZ) and I noticed that on the scale there are negative values. Typically radar reflectivity chart have only positive values on the scale and range from say 0 - 75dBZ for example.
What is the reason behind having or including negative dBZ values? Do they represent what would be weak or spurious radar returns especially at the edges of large positive contours?

[anikfal]

I am not expert in radar data. However, if having negative values is not technically wrong, you can display only positive values by specifying manual for the inquiry below, and then, set the minimum value equal to 0:

 Specify The Method Of Drawing Contours (1 or 2) for dbz:
1) Automatic
2) Manual