多普勒雷达PPI资料在数值模式MM5中的应用

Application of Doppler Radar PPI Datato the Numerical Model MM5

利用多普勒天气雷达观测的回波强度资料,估测大气的湿度值。假定回波强度大于4 0dBz的区域,相对湿度为1 0 0 % ,小于2 0dBz的区域相对湿度为90 % ,2 0～4 0dBz区域的相对湿度按线性变化求取。对应各点的温度值由MM5控制试验得出。然后通过迭代处理,求出对应各点的露点温度,通过以上步骤把雷达观测的回波强度值转换为模式中直接使用的物理变量,用于模式计算。为了验证该方法的可行性,进行了模拟试验,个例选用2 0 0 1年7月1 3日安徽全椒暴雨过程。背景场采用T2 1 3资料,加上常规探空,地面资料,通过分析形成控制试验的初始场。将安徽合肥新一代天气雷达观测的回波强度按上述方法加入到MM5中,形成敏感试验的初始场。水平网格为1 0 3×1 0 3,格距为1 0km ,垂直分33层,中心位置为31 0 0°N、1 1 7 6 6°E。试验结果表明,加入雷达资料后降水中心位置预报有明显改进。说明上述方法是可行的。

The atmospheric humidity are estimated with Doppler radar echo intensity. The relative humidity values are equaled to 100% in the areas of the echo intensity greater than 40dBz and relative humidity values are equaled to 90% in the areas of the echo intensity less than 20dBz, the relative humidity values are kept to linear correlation with the echo intensity in the areas of 20dBz-40dBz. The corresponding temperature values are gained by the control experimentation. Then the correspond dew point temperature values are calculated with iteration method from the humidity and temperature. Through these processes, radar echo intensity values are transformed to the variable values of the numerical model MM5 and are use in the MM5. The simulation experimentations are made to validate the method, the example is a heavy rainfall event in Quanjiao area, Anhui Province on the 13 July 2001.The background fields use the T213 data. The initial fields of control experimentation are evolved by the analysis from routine sounding and surface data. The echo intensity data of Hefei Doppler radar observations come into being the initial fields of MM5 sensitive experimentation. In this test the horizontal grids are 103×103,the distance is 10km, There are 33 levels at Perpendicularity, the central position is located at the point (31.00°N,117.66°E). The result shows that predicating precipitation areas are improved obviously and indicates that this method is feasible.