[Ref Safety first #22 July 2016 – 1/23]
Q: Why pilots should know the freezing level?
A: Pilots should know the freezing level because they could have more expectation about the threat of icing. Indeed, it might relate to the usage of WX radar.
In order to get accurate weather detection, the weather radar antenna should also be pointed toward lower levels (i.e. below freezing level), where water can still be found.
If a red area is found at a lower level, the antenna tilt should then be used to scan the area vertically. Presence of yellow or green areas at high altitudes, above a red cell, may indicate a very turbulent area.