【作者】 徐贤胜； 郭鹏；

【Author】 Xu Xian-Sheng~1,Guo Peng~2 1.Shanghai Institute of Applied Mathematics and Mechanics,Shanghai University,Shanghai,China 2.Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai,China

【机构】 上海大学上海市应用数学和力学研究所； 中国科学院上海天文台；

【摘要】 在大气多路径和噪声的条件下,滑动频谱方法无法获得较好的反演结果。本文提出一种改进的滑动频谱方法,即利用信号的振幅和谱能量信息对滑动频谱方法进行修正,削弱了信号中噪声的影响。通过信号的模拟和反演发现:高斯白噪声会造成滑动频谱方法获得的弯曲角与真值之间的偏离,而改进的滑动频谱方法不易受到噪声的影响,与真值较为接近。分别用滑动频谱方法和改进的滑动频谱方法对2007年第71天至73天共约4500个COSMIC掩星进行反演,将其折射率计算结果和atmPrf资料(通过全谱反演方法获得)一起,与ECMWF分析场资料进行统计比较。结果表明:滑动频谱方法在3 km～10 km和3 km以下分别存在着系统的正偏差和负偏差,改进的滑动频谱方法删除了信号中的部分噪声,减少了系统偏差;将改进的滑动频谱方法与全谱反演方法进行比较,发现两者具有相当的反演精度。更多还原

【Abstract】 Basic limitations of the sliding spectral(SS) method are the restriction of the resolution of bending angle profiles due to multipath effects and the noise in the moist lower troposphere.Above results are validated by simulations of atmospheric propagation using multiple phase screens technique under multipath conditions.A modified sliding spectral(MSS) method is developed to reduce these limitations in this paper.We demonstrate that MSS method can identify and decrease reasonably noise which may introduce retrieval errors in classical SS method,as well as further improve the resolution in the moist tropospheric regions.About 4500 COSMIC atmPhs profiles from DOY 71 to 73 in 2007 are analyzed using the SS method and MSS method,respectively.Statistical comparisons of the retrieval refractivity profiles show that the SS method contains systemic positive biases from 3 km to 10 km and systemic negative biases below 3 km.The MSS method has decreased the maximum positive bias from 0.37%to 0.23%at 7.6 km in the northern hemisphere,from 1.3%to 0.26%at 3.2 km in the tropics,from 0.66%to 0.16%at 3.1 km in the southern hemisphere in comparison with the SS method.Biases of the MSS method are close to that of COSMIC atmPrf profiles,which are inverted by full spectrum inversion(FSI) method,at all latitudes except in the tropical troposphere.更多还原