长江流域多普勒雷达回波强度资料对比分析

Quality Analysis of Echo Intensities from the Doppler Weather Radars in the Changjiang River Valley

利用 2 0 0 2年夏季长江中下游外场试验中几对双多普勒天气雷达资料 ,对比分析了同一时间、同一位置的S波段与C波段雷达的CAPPI和部分PPI回波强度资料。分析结果显示 ,宜昌和荆州雷达回波强度统计分布一致性较好 ,合肥、马鞍山、无为三部多普勒雷达回波强度统计分布一致性相对较差。回波强度资料的散点图表明 ,不同雷达回波强度资料之间的相关性较低。另外进一步证实C波段雷达在大范围降水区域需要进行降水的衰减订正。

The radar data, collected from the field experiment of the national fundamental program entitled ‘Mechanism and predict theory of disastrous weather over China', in the middle and lower reaches of the Changjiang River in the summer of 2002, are analyzed by the inter-comparison of the PPI and CAPPI echo intensities nearly simultaneously detected by the different radars but covering the same region. Four cases for such inter-comparisons are given out. The first two cases were observed at 05:00 BJT on June 21st, and at 03:00 BJT on June 24, 2002 respectively, using the S-band radar in Hefei, and C-band radars in Maanshan and Wuwei, Anhui Province, the lower reach of the Changjiang River. The last two cases were observed at 00:00 BJT on June 24, and 05:00 BJT on July 23, 2002 respectively using the S-band radar in Yichang, and C-band radar in Jingzhou, the middle reach of the Changjiang River. Statistical distribution of the echo intensities in each inter-comparison has a good agreement between the radars in Yichang and Jingzhou, however, pronounced difference among the three radars deployed in the lower reach. This may indicate that problems may exist in their initial calibrations. The low correlation is evident from the scattergrams of echo intensities among different radar observations. It is concluded that the location scheme of these radar data needs to be improved. In addition, the research confirms that the precipitation attenuation correction is need for the precipitation intensity measurement if by C-band radar is used.