风云三号降水卫星多角度偏振成像仪的观测特点和应用潜力

准确测量大气中云和气溶胶的辐射特性对数值天气预报和气候变化具有重要意义。搭载在风云三号降水卫星上的偏振载荷是国内首个具有短波红外通道的多角度偏振成像仪（Polarization and Multi Angle Imager, PMAI），计划于2023年年初发射，为气溶胶〖CD*2〗云〖CD*2〗降水观测链条提供重要支撑。该仪器运行在非太阳同步的倾斜轨道，可提供3 km（星下点）空间分辨率和700 km幅宽的图像。PMAI的观测通道包括1030 nm、1370 nm、1640 nm的偏振通道和相应的非偏振通道，可提供14个角度的观测信息。PMAI将利用自然目标的在轨替代定标和同平台仪器的交叉定标，实现5%的辐射测量精度。观测和仿真数据表明PMAI拥有描述云和气溶胶特性的独特优势。全新的短波红外通道的多角度偏振测量可以优化云相态识别和云微物理参数反演、气溶胶的地气解耦以及地表方向反射特征的表述。处于非太阳同步轨道的PMAI具有独特观测几何，可以获得大气粒子辐射更宽的散射角分布信息。此外，PMAI可联合同平台中分辨率光谱成像仪的可见近红外和热红外通道的观测信息，进行云和气溶胶的协同反演。〖JP〗

Observational Characteristics and Application Potential of Multi-Angle Polarization Imager onboard Fengyun-3 Precipitation Satellite

Accurate measurement of the radiative properties of clouds and aerosols is of great significance to global climate change and numerical weather prediction. The polarization payload mounted on the Fengyun 3 precipitation satellite is the first domestic multi angle polarization imager (PMAI) with short wave infrared channels. It is planned to be launched at the beginning of 2023, providing important support for the aerosol cloud precipitation observation chain. The instrument operates in a non sun synchronized inclined orbit and provides images with a spatial resolution of 3 km (sub satellite) and a width of 700 km. The observation channels of PMAI include 1030 nm, 1370 nm, and 1640 nm polarization channels and corresponding non polarization channels, which can provide observation information from 14 angles. PMAI will utilize on orbit vicarious calibration of natural targets and cross calibration of instruments on the same platform to achieve 5% radiometric accuracy. PMAI has the unique advantage of characterizing clouds and aerosols. The multi angle polarization measurement of the new short wave infrared channel can optimize cloud phase state identification and cloud micro physical parameter inversion, as well as ground air decoupling of aerosols, and at the same time, characterize surface directional reflection characteristics. The unique observation geometry of non sun synchronous orbits can make full use of the distribution characteristics of earth atmosphere radiation with scattering angles for parameter inversion. In addition, PMAI can optimize cloud and aerosol retrieval in conjunction with the observational information of the visible, near infrared and thermal infrared channels of the mid resolution spectral imager on the same platform.