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FC-型激光雷达对典型弱对流下低空风切变的监测研究

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

  • 摘要: 为了研究弱对流天气背景下的低空风切变特征,利用国产FC-Ⅲ型测风激光雷达多种扫描模式资料,对银川河东机场两次典型弱对流引发的低空风切变事件进行了研究。结果表明,两次弱对流过程是由高空槽过境引起的强迫抬升运动触发,过程影响前后均出现了风速增大、气温降低和气压升高的弱雷暴高压特征;激光雷达平面位置扫描模式可观测到降水所伴随的冷性下沉气流的扩散,在飞机起降关键区域形成了弱风区、辐散风区和辐合线,对飞行产生了影响;弱对流过程中风场在垂直方向上出现冷平流特征,降水前后上升气流转变为下沉气流,大的下沉速度对应大的地面风速;两次案例中激光雷达距离高度扫描(RHI)模式均探测到强风区的下降、触地辐散并沿跑道方向推移的过程,降水引起的冷性下沉气流在RHI图像中呈现“楔形”切入的特征。这些结果有助于民航预报员从激光雷达图像中识别弱对流天气下的低空风切变,为起降阶段的航空器提供有效的预警信息。

     

    Abstract: 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.

     

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