ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Echo Characteristics of Doppler Velocity in a Torrential Event
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Abstract:
Doppler radar, when used in detecting largescale intense precipitation, has it s echo features differing from the warm or cold advection alone (as an S or an tiS shape) and also differing from the largescale convergence or divergenc e (as a bowlike shape). The features of Doppler velocity resulting from the combination of warm or cold advection with c onvergence or divergence are called the complex windfield. Based on the Doppler weather radar data in Tanggu, AWS data and EVAD technique, analysis of Doppler weather radar data from an extensive, persistent strong rain fall event over the Hai river basin on August 16, 2005 was conducted and gave th e following results: (1) In the presence of a lowlevel complex windfield rel ated to the combination of warm advection and convergence, it can be seen from t he Doppler velocity products that, starting from the radar center, the clockwise curvature of a zerospeed line on one side toward the positive velocity zone i s more remarkable than the counterpart on the other side towards the negative ve locity zone, implying that when the negative speed zone is bigger compared to th e maximum positive area, rainfall is reinforced or maintained; (2) In the presen ce of a lowlevel complex windfield resulting from warm advection combined wit h divergence, the precipitation would be weakened or ceased. Therefore, the stud y on the convergence and divergence in the radar velocity field gives a good ind icator of nowcasting for the formation, development, maintenance and decay phases of a largescale rainfall event.
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