Insights into the Microwave Instruments Onboard the Fengyun 3D Satellite: Data Quality and Assimilation in the Met Office NWP System.

This paper evaluates the microwave instruments onboard the latest Chinese polar-orbiting satellite, Feng-Yun 3D (FY-3D). Comparing three months of observations from the Microwave Temperature Sounder 2 (MWTS-2), the Microwave Humidity Sounder 2 (MWHS-2), and the Microwave Radiation Imager (MWRI) to Met Office short-range forecasts, we characterize the instrumental biases, show how those biases have changed with respect to their predecessors onboard FY-3C, and how they compare to the Advanced Technology Microwave Sounder (ATMS) onboard NOAA-20 and the Global Precipitation Measurement Microwave Imager (GMI). The MWTS-2 global bias is much reduced with respect to its predecessor and compares well to ATMS at equivalent channel frequencies, differing only by 0.36 ± 0.28 K (1σ) on average. A suboptimal averaging of raw digital counts is found to cause an increase in striping noise and an ascending—descending bias. MWHS-2 benefits from a new calibration method improving the 183-GHz humidity channels with respect to its predecessor and biases for these channels are within ± 1.9 K to ATMS. MWRI presents the largest improvements, with reduced global bias and standard deviation with respect to FY-3C; although, spurious, seemingly transient, brightness temperatures have been detected in the observations at 36.5 GHz (vertical polarization). The strong solar-dependent bias that affects the instrument on FY-3C has been reduced to less than 0.2 K on average for FY-3D MWRI. Experiments where radiances from these instruments were assimilated on top of a full global system demonstrated a neutral to positive impact on the forecasts, as well as on the fit to the background of independent instruments. [ABSTRACT FROM AUTHOR]

摘要: 本文旨在对中国最新极轨气象卫星FY-3D搭载的微波遥感仪器进行评估。通过对FY-3D微波温度计II型(MWTS-2)、微波湿度计II型(MWHS-2)和微波成像仪(MWRI)连续三个月观测数据与英国气象局短期预报的比较验证,得到了仪器误差。研究了这些仪器与FY-3C的区别,同时与美国NOAA-20卫星搭载的先进技术微波探测器(ATMS)、美国国家航天局(NASA)全球降水测量卫星(GPM)搭载的微波成像仪(GMI)进行了比较。FY-3D MWTS-2的平均全球偏差值为0.36 ± 0.28 K (1σ),比FY-3C MWTS有较大降低,同时优于ATMS中同等频率的误差。仪器计数值的次优平均值会导致条带噪声的增加以及误差值的上升和下降。同时,利用一种新定标方法,FY-3D MWHS-2在183 GHz通道的性能得到了提高,优于FY-3C MWHS,与ATMS的偏差值在± 1.9 K之间。尽管在36.5 GHz(垂直极化)观测中检测到了短暂虚假的亮温,FY-3D MWRI在全球偏差和标准差上均优于FY-3C MWRI。对于FY-3D MWRI,受太阳影响的误差值较FY-3C降低到了0.2K。 [ABSTRACT FROM AUTHOR]