現業レーダデータを用いた土砂災害事例における線状降水帯の抽出

抄録

It has been recognized that a linear-shaped mesoscale convective system (LsMCS) causes the localized, torrential, and stationary rainfall. In this paper, the characteristics of LsMCS during sediment disaster events are investigated using radar data which has 5 minutes time interval and 1 km horizontal resolution. To extract the LsMCS from radar data, a contiguous regions of convective cell group is identified with more than 20 mm/h of rainfall intensity and more than 300 k㎡ of the area. The shape of the convective cell group is approximated as an ellipse and the motion vector is calculated from the change of position within the consecutive radar data using the correlation coefficient method. The characteristics of the shape, motion and rotation were analyzed using radar data in sediment disasters caused by LsMCS. As the result, it was found that the criteria for detecting LsMCS are as follows. (1) The aspect ratio (major axis/minor axis) of ellipse is more than about 2.0. (2) The motion vector of the ellipse is rotated in the counterclockwise direction from the long axis of the ellipse and the angle of rotation is less than about 22.5 degree. (3) The weighted center of convective cell group is shifted to the windward side as compared to the center of ellipse.