青藏高原地区COSMIC-2大气边界层高度探测性能研究

Evaluation of Data Quality and Reliability of COSMIC-2 in Atmospheric Boundary Layer Detection over the Tibetan Plateau

  • 摘要: 青藏高原复杂的地形和多样的下垫面条件对大气边界层的探测提出了巨大挑战。COSMIC-2作为新一代掩星探测卫星,具有高精度和全球覆盖的探测能力,在青藏高原大气边界层结构研究领域具有很强的应用潜力,然而,其在该地区的探测性能仍需深入评估。本研究基于2019年10月和2022年6月的第二次青藏高原科学考察“地-气相互作用与气候效应”立体综合加强期观测试验数据和ERA5再分析数据,系统评估了COSMIC-2掩星观测的大气廓线数据和边界层高度估算的精度。结果表明:COSMIC-2的气温和大气折射率数据与观测数据一致性较高,平均偏差分别为−0.02 ℃和0.34,能够准确反映1~6 km对流层中低层的垂直分布;基于折射率梯度法计算的边界层高度平均偏差为−0.16 km,优于其他估算方法且能较好捕捉边界层高度的日变化趋势,各站点日平均高度的相关系数在0.61~0.87,平均偏差小于0.3 km;然而,COSMIC-2在东部的季节变化中未能准确反映水汽对边界层的影响,尤其在夏季表现出明显的正偏差(约1.1 km)。总体而言,COSMIC-2数据适用于青藏高原中高对流层结构和边界层高度变化的监测,但在低层稳定边界层的探测中存在不足。

     

    Abstract: The complex terrain and various underlying surface conditions of the Tibetan Plateau present significantly challenges for accurate detection of the atmospheric boundary layer. COSMIC-2, a GNSS-RO satellite, offers high-precision and global observation capabilities, making it a promising tool for atmospheric boundary layer research over the Tibetan Plateau. However, its performance in this region has not yet been comprehensively evaluated. This study utilized observational data from the intensive observation period of the “Land-Atmosphere Interaction and Climate Effects” campaign during the Second Tibetan Plateau Scientific Expedition and Research in October 2019 and June 2022, as well as ERA5 reanalysis data, to systematically assess the accuracy of COSMIC-2 atmospheric profile data and boundary layer height estimates. The results demonstrate that COSMIC-2 temperature and atmospheric refractivity data show high consistency with observational data, with mean biases of −0.02 ℃ and 0.34, respectively, effectively capturing the vertical distribution of the lower to mid-troposphere (1~6 km). Boundary layer height estimates derived from the refractivity gradient method exhibited a mean bias of −0.16 km, performing other estimation methods. Moreover, COSMIC-2 effectively captured the diurnal variations of boundary layer height, with correlations of 0.61–0.87 between COSMIC-2 and ground-based observations, and a mean bias of less than 0.3 km across different observation sites. However, in the eastern Tibetan Plateau, COSMIC-2 data did not adequately reflect the influence of water vapor on seasonal boundary layer variations, particularly during summer, where a significant positive bias of approximately 1.1 km was observed. Overall, COSMIC-2 data are well-suited for monitoring mid-to-upper tropospheric structures and boundary layer height variations over the Tibetan Plateau but exhibit limitations in detecting stable lower boundary layers. These findings provide valuable insights into the application of COSMIC-2 data for atmospheric boundary layer studies over complex terrain and contribute to advancing the understanding of boundary layer processes in the Tibetan Plateau region.

     

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