Direct assimilation of Chinese FY-3C Microwave Temperature Sounder-2radiances in the global GRAPES system
Direct assimilation of Chinese FY-3C Microwave Temperature Sounder-2radiances in the global GRAPES system
复制标题
DOI：
10.5194/amt-9-3095-2016
复制
发表时间：
2016-07
影响因子：
3.8
通讯作者：
Juan Li;Guiqing Liu
中科院分区：
文献类型：
--
作者：
Juan Li;Guiqing Liu
抽象的。风云三号C卫星是我国一颗携带新一代微波探测仪器的极轨业务卫星。本文介绍了中国气象局全球和区域同化预报系统（GRAPES）对FY-3C微波温度探测仪-2（MWTS-2）辐射资料的同化。提出了一种同化MWTS-2辐射的质量控制方法。同化前的广泛监测表明，MWTS-2观测表现出明显的条纹图案。结合主成分分析（PCA）和集成经验模式分解（EEMD）的技术被施加到观测，以消除条带噪声。通过应用可见光和红外辐射计（VIRR）云分数阈值76%来识别多云视场（FOV）。其他质量控制步骤按以下顺序进行：（i）删除沿海FOV，（ii）不使用8个最外FOV，（iii）不使用海冰和陆地上的通道5数据，（iv）如果地形高度高于500 m，则不使用通道6观测值，以及（v）删除观测值和模型模拟之间差异较大的离群值。通道5-8的拟定QC分别删除了约83%、75%、40%和40%的观察结果。经过QC后，全局偏差和标准差显着降低。MWTS-2辐射的同化显示出积极的影响时，控制实验只同化常规观测。实验还表明，当从观测值中去除条带噪声时，分析和预测误差略有减小。提取条带噪声的质量控制方案有助于提高分析和预报的准确性。当常规数据和其他卫星数据都被同化时，MWTS-2的影响是中性的。
Abstract. FengYun-3C (FY-3C) is an operational polar-orbiting satellite carrying the new-generation microwave sounding instruments in China. This paper describes the assimilation of the FY-3C Microwave Temperature Sounder-2 (MWTS-2) radiances in the Global and Regional Assimilation and PrEdiction System (GRAPES) of China Meteorological Administration. A quality control (QC) procedure for the assimilation of MWTS-2 radiance is proposed. Extensive monitoring before assimilation shows that MWTS-2 observations exhibit a clear striping pattern. A technique combining principal component analysis (PCA) and ensemble empirical mode decomposition (EEMD) is applied to the observations to remove the striping noise. Cloudy field-of-views (FOVs) are identified by applying the Visible and InfrarRed Radiometer (VIRR) cloud fraction threshold of 76 %. Other QC steps are conducted in the follow order: (i) coastal FOVs are removed, (ii) eight outmost FOVs are not used, (iii) channel 5 data over sea ice and land are not used, (iv) channel 6 observations are not used if the terrain altitudes are higher than 500 m, and (v) outliers with large differences between observations and model simulations are removed. Approximately 83, 75, 40, and 40 % of the observations are removed by the proposed QC for channels 5–8, respectively. After QC, the global biases and standard deviations are reduced significantly. The assimilation of the MWTS-2 radiances shows a positive impact when the control experiment assimilates only conventional observations. The experiments also show that the analysis and forecast errors are slightly reduced when the striping noise is removed from the observations. The quality control scheme of extracting the striping noise may contribute to the analysis and forecast accuracy. The impact of MWTS-2 is neutral when the conventional data and other satellite data are all assimilated.