Research on the monitoring of low-level wind shear under typical weak convection by FC-Ⅲ LiDAR

In order to study the characteristics of low-level wind shear under the background of weak convection weather, low-level wind shear events caused by two typical weak convection events in Yinchuan Hedong Airport were studied using a variety of scanning modes of domestic FC-Ⅲ type wind light detection and ranging (LiDAR). The results show that, two weak convection processes were triggered by the forced uplift caused by the passage of the high-altitude trough. Before and after the process, the characteristics of weak thunderstorm high appeared, such as wind speed increase, air temperature decrease and air pressure increase. The diffusion of cold downdraft associated with precipitation can be observed by LiDAR plane position indicator mode. Weak wind area, divergent wind area and convergence line have been formed in the key area of aircraft takeoff and landing, which has an impact on flight. In the process of weak convection, the wind field is characterized by cold advection in the vertical direction. The updraft changes into downdraft before and after precipitation, and the large downdraft speed corresponds to the large ground wind speed. In both cases, the process of descending, touchdown divergence and moving along the runway in the strong wind area were detected by LiDAR range height indicator (RHI) mode. The cold downdraft caused by precipitation presents a "wedge" cut in feature in RHI image. These results are helpful for civil aviation forecasters to identify low-level wind shear in weak convective weather from LiDAR images, and provide effective early warning information for aircraft in takeoff and landing phase.