Fig.  shows the radar echo energy of the four tilted beams with different tilted angles observed by the Wuhan MST radar using the low mode (unit: dB), which is the average value of three observation cases (LT: 2011-03-17, 08:30-10:00; 2011-03-15, 18:00-19:30; 2011-03-15, 19:30-21:00).