Analysis on Radar Characteristics in a Convective Rain Process

The characteristics of the radar echo in a heavy rain process in Beichuan, Sichuan during September 22-23 is analyzed by using new generation Doppler radar data and rainfall data from auto-station as well as reflectivity factor, liquid state content and scanned rainfall.The result shows that 1) heavy convective rainstorm cell in Sichuan Basin is of such characteristics as inclining-forward, low centroid and overhanging, in addition, it moves slowly.2) The low-elevation reflectivity factor corresponds well to rainfall, in other words, the stronger the echo in elevation from 2.4 to 6.0 degree, the heavier the rainfall.If the echo at elevation 2.4 degree is bigger than 50dbz, the rainfall intensity will be more than 1mm/s.3) the heavy convective rainstorm cell in Sichuan Basin lowers its centroid while it fades away.When the intensity of echo at elevation 6.0 degree decreases sharply, the rain reduces correspondingly.4) The jumping increase of the echo intensity is another feature of heavy convective rainstorm in Sichuan Basin.When the increase rate of the echo intensity at low elevation is over 14dbz/body-scan with the increase rate of liquid water in air column more than 10kg/m², the heavy rain is most likely to take place in 20-30 minute, which is an practicable pre-warning index in short time rainstorm prediction.