通过影响高度多路径质量控制改进热带对流层低层GPS掩星资料同化效果  

Impact multipath quality control improving GPS RO data assimilation in the tropical lower troposphere

作　　者：邹晓蕾[1] 刘辉 ZOU Xiaolei;LIU Hui(Joint Center of Data Assimilation for Research and Application,Nanjing University of Information Science&Technology,Nanjing 210044,China;Earth System Science Interdisciplinary Center(ESSIC),University of Maryland,20740,USA)

机构地区：[1]南京信息工程大学资料同化和应用中心,江苏南京210044 [2]马里兰大学地球系统科学交叉学科中心,马里兰州20740

出　　处：《大气科学学报》2020年第1期116-127,共12页Transactions of Atmospheric Sciences

基　　金：国家重点研发计划资助项目(2018YFC1507004)。

摘　　要：与观测气象、电离层和气候的GPS卫星计划COSMIC-1相比,COSMIC-2有更大功率的GPS接收天线,高2倍的采样率(100 Hz),小3倍的轨道倾角(24°)。因此,COSMIC-2和未来小卫星将为热带地区提供前所未有的大量无线电掩星观测资料。因为热带对流层低层水汽含量高,折射率有局地大梯度,违背大气球对称性假定,造成影响多路径现象,所以热带地区的掩星资料同化具有较大挑战性。本文首先利用之前研究中提出的影响参数多路径质量控制方法,去除热带对流层低层弯角模拟中出现影响参数多路径现象的资料,然后使用有限射线长度二维(2D)路径追踪观测算子和一维(1D)Abel变换观测算子,进行GPS弯角资料同化。结果表明,如果射线路径限制在离近地面点±300~400 km的水平距离以内,有限射线长度2D路径追踪观测算子得到的弯角模拟与2D射线追踪观测算子得到的弯角廓线之差不仅无偏,而且其标准差远比1D Abel的弯角模拟精度高。此外,无论采用1D Abel变换还是有限射线长度2D路径追踪观测算子来模拟弯角,影响参数多路径质量控制方案都能进一步改进GPS掩星弯角资料同化和预报精度。The Constellation Observing System for Meteorology,Ionosphere,and Climate(COSMIC-2) has more powerful GPS receiver antennas,a twice higher sampling rate of 100 Hz,and a three times smaller inclination of 24°than those of COSMIC-1.COSMIC-2 will,therefore,provide an unprecedented ample number of radio occultation(RO) data in the tropics.Assimilation of RO data in the tropics is challenging due to unique features such as large horizontal gradients of refractivity,spherical asymmetry,and impact multipath in the moist tropical lower troposphere.Bending angle data assimilation in the tropical lower troposphere is done in this study using a two-dimensional(2 D) limited-ray-path raytracing operator and a one-dimensional(1 D) Abel transform operator.An impact multipath quality control(QC) developed in our previous study is incorporated to eliminate occurrences of impact multipath in bending angle simulations.The fractional differences in bending angle simulations between the limited-path-length raytracing operators and the original 2 D raytracing operator have zero bias,and their standard deviations are more than three times smaller than those between the 1 D Abel transform operator and the 2 D raytracing operator.The highest accuracy and precision are achieved for the 2 D limited-ray-path ray tracing operator if the ray path is confined within±400 km.Use of the physically based impact multipath QC is shown to improve COSMIC data assimilation and forecast results using either the 1 D Abel transform or the 2 D limited-ray-path observation operators of bending angle in the tropical lower troposphere.

关 键 词：GPS掩星弯角资料同化 有限射线长度2D路径追踪观测算子 影响参数多路径质量控制 

分 类 号：P228.4[天文地球—大地测量学与测量工程] P412[天文地球—测绘科学与技术]