京津冀地区无人机航路气象因子高分辨率模拟分析

京津冀地区低空环境复杂多变,低空飞行安全受到雷暴、风切变、能见度、温度和湿度等气象因子的影响,准确地模拟和预报无人机低空航路上的气象要素是一个难题。基于中尺度天气预报模式(WRF)及其先进的三维变分同化系统(3D-Var),论文以2016年华北“7·20”特大暴雨作为研究案例,对京津冀地区无人机低空航路上的温度场、湿度场和风场进行资料同化与数值模拟,对比地面观测资料和数值模拟结果,分析其结构及特征,以期为京津冀地区无人机航路飞行安全保障提供参考。结果表明：WRF模式能够较好地模拟出该地区近地面温度、湿度和风速的日变化趋势。平原站点(天津和密云)模拟值与观测值的均方根误差(RMSE)和偏差(Bias)较小,风速在山区的模拟值偏大,平原地区的模拟效果优于北部和西部山区。强降水发生时,平原地区和山区的温度相差15 ℃左右,相对湿度达95%以上,边界层高度低于500 m,强烈的温差、较高的湿度和较低的边界层都会影响无人机的飞行安全。900 hPa高空,沿117°E经线在河北省廊坊—衡水一线出现超过10 m·s^-1的风速值,形成强劲的东北风,区域北部(39°N~40.5°N)出现了明显的上升气流,1000 m高度处垂直风速也超过2 m·s^-1。强烈的上升气流极不利于无人机的飞行,会对无人机飞行姿态和飞行高度产生重大影响,造成安全隐患。

High-resolution simulation analysis of meteorological factors of unmanned aerial vehicle air route in the Beijing-Tianjin-Hebei region

The low-altitude air route environment in the Beijing-Tianjin-Hebei region is complex and unstable. The safety of low-altitude flight is mostly affected by meteorological factors such as thunderstorms, wind shear, low visibility, and extreme temperature and humidity. It is difficult to accurately simulate and forecast the meteorological elements on the low-altitude air route of the unmanned aerial vehicle (UAV). Based on the mesoscale Weather Research and Forecasting (WRF) model and its advanced three-dimensional variational assimilation system (3D-Var), we took the "7·20" heavy rainfall of North China in 2016 as a study case. The temperature field, humidity field, and wind field of the UAV low-altitude air route in the Beijing-Tianjin-Hebei region were simulated, and the ground observation data and numerical simulation results were compared and analyzed. The aim was to provide a reference for the flight safety of UAVs in the Beijing-Tianjin-Hebei region. The conclusion is as follows: WRF model can better simulate the daily variation trend of near-surface temperature, humidity, and wind speed in this area. The root mean square error (RMSE) and the bais between the simulated values and the observed values of the plain sites (Tianjin and Miyun) is lower, the wind speed simulations in mountainous areas is higher, and the simulation effect in plain areas is better than that in the northern and western mountainous areas. When heavy rainfall occurs, the temperature difference between the plain areas and the mountainous areas is about 15 ℃, the relative humidity is above 95%, and the boundary layer height is less than 500 m. The strong temperature difference, higher humidity, and lower boundary layer will affect UAV flying performance. At an altitude of 900 hPa along the 117°E longitude line, a wind speed of more than 10 m·s^-1 appeared in Langfang-Hengshui in Hebei Province, forming a strong northeast wind. The northern part of the region (39°N-40.5°N) has a clear updraft. The vertical wind speed at a height of 1000 m also exceeds 2 m·s^-1. The strong updraft is extremely unfavorable to the flight of the UAV, and will have a significant impact on the flight attitude and flying height of the UAV, causing potential safety hazards.