分类型最优法在江苏沿江地区降水估测中的应用与讨论

为提高现有天气雷达产品生成模块中处理系统算法精度、并为其他短时临近预报系统或数值预报模式提供合适的Z-I关系为目的,选择江苏沿江地区作为试验区域,采用分类型最优法建立相应的Z-I关系,并比较分类型最优法与单一Z-I关系对过程雨量和分段雨量的估测能力.结果表明:分类型最优法比单一Z-I关系法明显提高过程雨量估测的精度,梅汛期降水估测精度提高近2.5倍,夏季台风降水估测由低估72％降低至低估45％.对不同雨量段进行估测比较后发现,分类型最优法对强降水雨量段改善较为明显,对雨强＞ 10 mm/h的梅汛期对流云降水和台风降水所有雨量段的雨量估测改善明显.最后在气候统计的基础上,通过改进雷达估测降水产品色标数值等级,以达到优化雷达估测降水产品图像的显示能力.

The application and discussion of classified optimization method on estimating precipitation in the region around Yangtze River in Jiangsu province

In order to improve the precision of precipitation processing system algorithm in weather radar products generators, as well as provide a suitable Z-I relationship for other nowcasting systems or numerical prediction models,the classified optimization method is used to establish Z-I relationship in the region around Yangtze River in Jiangsu province chosen as a test region under the premise of improving the estimation of precipitation accuracy. A comparison of the precipitation capacity estimation between the classified optimization method and the single Z-I relationship is made in the rain course and the segmental rain amount. The results show that the precipitation capacity estimation of the rain course is significantly improved by the classified optimization method compared with the single Z-I relationship. Estimation of Meiyu rainfall increases nearly 2.5 times. Underestimation of the summer typhoon rainfall decreases from 72% to 45%. By comparison in estimating the segmental rain amount, it is found that there is a distinct improvement of heavy precipitation by the classified optimization method in the Meiyu rainfall, rainfall whose amount is greater than 10mm/h and typhoon rainfall. Finally, on the basis of climate statistics, the improvement of radar quantitative precipitation product color value level is made to optimize the estimation of precipitation product image display capability.