Uncertainly quantification of lidar-derived wake vortex parameters with/without data assimilation

In this study, the uncertainty quantification of wake vortex parameters measured by a Doppler lidar is conducted to assess the errors of the lidar-derived parameters due to the measurement process. We employ three methods to estimate vortex parameters from lidar measurements: a simple method to detect velocity peaks on the measurement plane, and a least-square fitting of a vortex model to lidar velocity. In addition, wake vortex parameters along with a surrounding wind field are estimated based on the four-dimensional variational (4D-Var) method assuming a velocity field obtained by the Rosenhead-Burnham-Hallock vortex model. With the last approach, vortex parameters are obtained considering the factors such as insufficient resolution in the line-of-sight direction and vortex movement during a laser scan. It is confirmed from numerical experiments that the average circulation is significantly underestimated and core radius becomes too large with the simple method. The least-square fitting reduces the deviation of output/input parameter ratios. On the other hand, vortex parameters estimated with the help of the 4D-Var method are further improved by compensating the errors due to the measurement process.