Further...
You adjust the RADAR antenna tilt, based on the range you're looking at and the aircraft's altitude. This has nothing to do with the aircraft's pitch.
Some SOPs require 4 degrees up on the RADAR for takeoff...some as high as 7. As you climb to altitude, you'll be adjusting downward the RADAR tilt.
Airbus has a great publication, "Optimal Use of Weather RADAR". It explains very well the 'how' and 'why' you adjust the RADAR antenna tilt.
One of the most common errors I see is the overscanning of weather. This is the result of not pointing the RADAR tilt down sufficiently to see the returns. CBs show the greatest returns at the freezing level. CB tops may show little, if any, return...but turbulence can be severe.
As Dreamland mentioned, the auto RADARs (multiscan) today do a great job of knowing where to have the tilt.
PantLoad