Fengyun Radiation Services for Solar Energy Meteorology:Status and Perspective

Satellite remote sensing is essential for solar energy meteorology. The 14-channel Advanced Geostationary Radiation Imager of the Fengyun-4 series of satellites performs a full-disc scan over greater China every 15 min, providing highgranularity information that allows the retrieval of cloud properties, aerosol optical depth, and precipitable water vapor content, which can facilitate the acquisition of surface solar irradiance components through physical methods. Machinelearning methods have also shown potential in providing accurate end-to-end surface solar radiation retrievals. Albeit the physical principles of irradiance retrieval and machine-learning algorithms are fairly well known, the public service concerning disseminating the irradiance product to the energy and power industry still lacks robustness and consistency. In this perspective article, the status quo of Fengyun-4 irradiance products is first reviewed. Then, from the perspective of solar resource assessment and forecasting, three fundamental characteristics of the kind of irradiance products that are most serviceable to the solar energy sector are identified, namely, coverage, timeliness, and accessibility. Finally, an outlook on the new-generation Fengyun radiation service is put forward, and the prospective scientific and practical challenges are elaborated.