典型河谷城市温湿垂直廓线变化特征及模拟 研究

Study on Variation Characteristics and Simulation of Vertical Profiles of Temperature and Humidity in Typical Valley Cities

摘要: 本研究以典型河谷城市西昌为研究对象，利用2021至2025年探空观测数据，系统分析了温度、相对湿度的垂直廓线变化特征。基于WRF模式设置YSU、MYJ和ACM2三种边界层参数化方案，评估其对垂直结构的模拟能力，并基于优选方案分析冬季气象要素的日变化垂直结构特征。结果表明：温度整体随海拔升高逐步降低，相对湿度呈现近地面偏高、中层偏干的垂直分布特征；季节变化方面，夏季近地面气温最高、空气垂直混合较为充分，中层大气较为干燥，春、秋季特征介于冬夏之间；三种方案对温湿廓线模拟均表现良好，MYJ方案在湿度模拟中表现最优，推荐为西昌河谷地区的优选边界层参数化方案。基于MYJ方案的冬季日变化分析表明，夜间至清晨近地面大气层结稳定，大气高湿，午后逆温逐渐消散，垂直扩散条件明显改善。研究结果为河谷城市边界层参数化方案选择以及区域大气污染防控提供科学依据。

Abstract: Taking Xichang, a typical valley city, as the study area, this paper analyzes vertical profiles of temperature and relative humidity based on 2021~2025 radiosonde data. Three boundary layer parameterization schemes (YSU, MYJ and ACM2) were configured within the WRF model to compare their capabilities in reproducing vertical atmospheric structures. Using the optimal scheme, we further analyzed the diurnal vertical variations of winter meteorological elements. The results indicate that temperature declines steadily with altitude, whereas relative humidity features a vertical profile with high values in the near-surface layer and dry conditions in the mid-troposphere. For seasonal differences, summer witnesses the highest near-surface temperature accompanied by intensive vertical atmospheric mixing and a drier mid-troposphere; spring and autumn exhibit transitional features between winter and summer. All three schemes reasonably reproduce temperature and humidity profiles. The MYJ scheme outperforms the others in humidity simulation, so it is proposed as the preferred boundary layer scheme for the Xichang valley. Winter diurnal analysis based on the MYJ scheme suggests stable stratification and high humidity near the surface from night to early morning. Temperature inversions break down in the afternoon, greatly facilitating vertical atmospheric diffusion. Those results offer scientific support for boundary layer scheme selection and regional air pollution control in valley cities.