Improvement of vertical velocity measurements, part 3.4B

Vertical velocities are assumed to be measurable with vertically pointing antenna beams. An exact horizontal levelling and good phase calibration of the radar antenna system can yield real main-beam directions which do not significantly differ from calculated patterns. It is, thus, anticipated that antenna beams can be pointed exactly vertically. Because of area size and near-field limitations, VHF radar antennas have typically beam widths of more than several degrees. It is known that most of the reflectivity structures detected by vertically beaming VHF radars in the troposphere, stratosphere and lower mesosphere are aspect-sensitive. It cannot a priori be assumed that these structures are exactly horizontal. A few examples are investigated to support this statement.