QuikSCAT风矢量快速反演的后向散射系数预处理算法

A quick-look wind-vector retrieval algorithm for QuikSCAT

根据QuikSCAT的工作特点,提出了一种通过对QuikSCAT风矢量单元后向散射系数进行预处理,从而提高反演效率的快速算法。预处理算法将每个风矢量单元对应的后向散射系数按测量几何关系分为外波束前视、内波束前视、内波束后视、外波束后视观测4组,取每组后向散射系数平均值作为对应组的测量结果,再将作分组平均处理后的后向散射系数代入反演流程中,使得求目标函数值步骤中搜索查找表的次数减少到4次。与JPL业务化运行所选用的算法相比较,快速算法仅以损失少量风向信息为代价,将风矢量反演所需计算量减少到原来的1/3,极大地提高了运算效率,缩短了风矢量反演所需的时间,可为应对突发灾难性天气等特殊情况争时间。

A quick-look wind-vector retrieval algorithm for the QuikSCAT is proposed, which combines the back scattering coefficients into four groups： fore-look and back-look of the inner beam, and fore-look and back-look of the outer beam. By taking the average of the measurements binned into each group to represent the back scattering coefficient for each measurement geometry, the operation times of checking the look-up table, which aims to get the MLE （Maximum-Likelihood Estimator） value of the wind vector, is reduced from about ten to four for each guess of wind speed and direction, greatly improving the computing efficiency. Compared with the Jet Propulsion Laboratory （JPL） operational wind-vector retrieval process, the computing time of our quick-look method is only 1/3 of the JPL＇s despite of its disadvantage of partial loss of wind direction information. Therefore the quick-look method is potentially useful for a rapid response to paroxysmal disaster weather.