A rain-type adaptive pyramid Kanade-Lucas-Tomasi (A-PKLT) optical flow method for radar echo extrapolation is proposed. This method introduces a rain-type classification algorithm that can classify radar echoes into six types: convective, stratiform, surrounding convective, isolated convective core, isolated convective fringe, and weak echoes. Then, new schemes are designed to optimize specific parameters of the PKLT optical flow based on the rain type of the echo. At the same time, the gradients of radar reflectivity in the fringe positions corresponding to all types of rain echoes are increased. As a result, corner points that are characteristic points used for PKLT optical flow tracking in the surrounding area will be increased. Therefore, more motion vectors are purposefully obtained in the whole radar echo area. This helps to describe the motion characteristics of the precipitation more precisely. Then, the motion vectors corresponding to each type of rain echo are merged, and a denser motion vector field is generated by an interpolation algorithm on the basis of merged motion vectors. Finally, the dense motion vectors are used to extrapolate rain echoes into 0–60-min nowcasts by a semi-Lagrangian scheme. Compared with other nowcasting methods for four landfalling typhoons in or near Shanghai, the new optical flow method is found to be more accurate than the traditional cross-correlation and optical flow methods, particularly showing a clear improvement in the nowcasting of convective echoes on the spiral rainbands of typhoons.

提出了一种用于雷达回波外推的雨型自适应金字塔Kanade-Lucas-Tomasi (A-PKLT)光流方法。该方法引入了雨型分类算法，可以将雷达回波分为六种类型：对流回波、层状回波、周围对流回波、孤立对流核心、孤立对流条纹和弱回波。然后，设计新方案以根据回波的降雨类型优化 PKLT 光流的特定参数。同时，所有类型的雨回波对应的条纹位置的雷达反射率梯度都增大。结果，将增加作为周围区域中用于 PKLT 光流跟踪的特征点的角点。因此，在整个雷达回波区域有目的地获得更多的运动矢量。这有助于更准确地描述降水的运动特征。然后，将每种类型的雨回波对应的运动矢量进行合并，在合并后的运动矢量的基础上，通过插值算法生成更密集的运动矢量场。最后，密集运动矢量用于通过半拉格朗日方案将雨回波外推为 0-60 分钟的临近预报。与上海及附近4个登陆台风的临近预报方法相比，新的光流方法比传统的互相关和光流方法更准确，特别是螺旋上对流回波的临近预报有明显改善。台风雨带。将每种类型的雨回波对应的运动矢量进行合并，在合并后的运动矢量的基础上，通过插值算法生成更密集的运动矢量场。最后，密集运动矢量用于通过半拉格朗日方案将雨回波外推为 0-60 分钟的临近预报。与上海或附近4个登陆台风的临近预报方法相比，新的光流方法比传统的互相关和光流方法更准确，特别是螺旋上对流回波的临近预报有明显改善台风雨带。将每种类型的雨回波对应的运动矢量进行合并，在合并后的运动矢量的基础上，通过插值算法生成更密集的运动矢量场。最后，密集运动矢量用于通过半拉格朗日方案将雨回波外推为 0-60 分钟的临近预报。与上海及附近4个登陆台风的临近预报方法相比，新的光流方法比传统的互相关和光流方法更准确，特别是螺旋上对流回波的临近预报有明显改善。台风雨带。密集运动矢量用于通过半拉格朗日方案将雨水回波外推到 0-60 分钟的临近预报中。与上海或附近4个登陆台风的临近预报方法相比，新的光流方法比传统的互相关和光流方法更准确，特别是螺旋上对流回波的临近预报有明显改善台风雨带。密集运动矢量用于通过半拉格朗日方案将雨水回波外推到 0-60 分钟的临近预报中。与上海或附近4个登陆台风的临近预报方法相比，新的光流方法比传统的互相关和光流方法更准确，特别是螺旋上对流回波的临近预报有明显改善台风雨带。