Two-Dimensional Identification of Low-Level Wind Shear at a Complex-Terrain Airport Using Doppler Wind Lidar Observations

Low-level wind shear (LLWS) poses a significant hazard to aircraft operating at airports in complex terrain, where wind fields may vary rapidly across the airport vicinity. This study examines the spatial evolution of LLWS-related wind structures at Xining Caojiapu International Airport (ZLXN) using 3°-elevation Doppler wind lidar (DWL) plan position indicator (PPI) observations and a combined shear identification algorithm (CSIA). The CSIA combines range- and tangential-direction gradients of radial velocity to identify enhanced-gradient regions. A convective event on 29 May 2021 exhibited a rapidly developing divergent outflow, whereas a cold-front-induced event on 1 November 2021 featured a propagating shear boundary associated with cold-air intrusion. In both cases, the identified regions were consistent with radial velocity discontinuities and the approximate locations and times of aircraft-reported LLWS encounters. Of 66 pilot reports collected during 2019–2023, 61 were retained for verification, of which 49 were detected, yielding a report-based probability of detection PODPIREP of 80.3% (95% cluster-bootstrap confidence interval: 69.2–89.8%). The observed PODPIREP values were 93.9%, 83.3%, 66.7%, and 28.6% for convective-related, cold-front-induced, downward-momentum-transfer-related, and other events, respectively. These results support PPI-based identification of LLWS-related radial velocity structures, but do not establish overall operational alerting performance.