利用FY-3C折射率对大气边界层高度的反演与分析

Inversion and Analysis of Atmospheric Boundary Layer Height Using FY-3C Radio Occultation Refractive Index Data

  • 摘要: 2013年中国发射了首颗进行全球导航卫星系统(global navigation satellite system,GNSS)掩星观测的气象卫星风云3号C星(Fengyun-3C,FY-3C),且已发布自2014年6月以来的FY-3C掩星大气产品,但目前还未见将其应用于大气边界层的相关研究。首次尝试利用FY-3C折射率产品确定边界层高度并进一步进行空间分布分析。结果表明,在小波协方差变换法基础上, 进行尖锐度约束,能够确定FY-3C掩星低层大气折射率廓线中可能存在的突变,反演边界层高度。所得到的2015―2018年各年边界层高度全球分布在不同纬度及海洋和陆地上的差异基本体现了边界层与地表气候及地形的关系,但FY-3C折射率产品在低层大气的精度和垂直分辨率相对较低。因此,反演成功率总体上较低,反演结果对边界层高度空间分布细节特征的呈现仍有待提升。

     

    Abstract:
      Objectives  The first meteorological satellite for global navigation satellite system (GNSS) radio occultation (RO) observation of China, Fengyun-3C (FY-3C), whose products have been released since June 2014, was launched in 2013. But the references about the application of FY-3C RO data in the study of atmospheric boundary layer height (ABLH) are still not available.
      Methods  Firstly, we derived ABLH values by the wavelet covariance transform (WCT) method, based on FY-3C RO refractive index data. Secondly, the feasibility of the method was verified by representative and statistical comparison with the ABLH inversion results of COSMIC (constellation observing system for meteorology ionosphere and climate) RO refractive index data. Then, we presented the global distribution of FY-3C ABLHs, and made a detailed analysis.
      Results  The heights of steep transitions in the FY-3C RO refractivity index profiles of lower atmosphere, which correspond to the ABLHs, can be derived by using the WCT method with constraints on relative sharpness. The latitudinal differences and land-sea differences in the global distributions of ABLHs basically reflect the relationship between ABLH and climate and topography.
      Conclusions  Because of the low precision and vertical resolution of FY-3C RO products in the lower atmosphere, the success rate for the inversion process is not high on the whole, and the representations on the detailed characteristics of the distribution of ABLH need to be improved.

     

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