Extensive Validation of FENGYUN-4A AGRI Layer Water Vapor Products

China is developing a new generation of geostationary meteorological satellites called Fengyun-4 (FY-4), which is planned for launch beginning in 2016. Following upon the current FY-2 satellite series, FY-4 will carry four new instruments: the Advanced Geosynchronous Radiation Imager (AGRI), the Geosynchronous Interferometric Infrared Sounder (GIIRS), the Lightning Mapping Imager (LMI), and the Space Environment Package (SEP). The first satellite FY-4A of the FY-4 series launched on 11 December 2016 is experimental, and the following four or more satellites will be operational.

The main objectives of the FY-4 series are to monitor rapidly changing weather systems and to improve warning and forecasting capabilities. FY-2 satellites carry the Visible and Infrared Spin Scan Radiometer (VISSR) capable of imagery in five spectral bands. Derived products include atmospheric motion vectors (AMVs), sea surface temperatures (SSTs), total precipitable water vapor (TPW), quantitative precipitation estimations (QPEs), fire locations and intensity, surface albedo, and several others. FY-4A AGRI has 14 spectral bands (increased from the five bands of FY-2) that are quantized with 12 bits per pixel (up from 10 bits for FY-2) and sampled at 1 km at nadir in the visible (VIS), 2 km in the near infrared (NIR), and 4 km in the remaining IR spectral bands (compared with 1.25 km for VIS, no NIR, and 5 km for IR of FY-2). FY-4 will improve most products of FY-2 and introduce many new products [such as atmospheric temperature and moisture profiles, atmospheric instability indices, layer precipitable water vapor (LPW), rapid developing clouds, and others]. Products from FY4 series are expected to provide enhanced applications and services. FY-4A AGRI has more than one water vapor bands (compare to FY-2) so that not only two-dimensional but three-dimensional water vapor structure will be detected.

In this research, an extensive validation of FY-4A AGRI layer water vapor products were carried out based on NCEP, ERA, Sounding data, T639, TERRA/AQUA MODIS and Himawari-8 AHI data. In which NCEP, ERA, TERRA/AQUA MODIS, Himawari-8 AHI data were used to validate the total layer water vapor products and NCEP, ERA, Sounding data, T639, Himawari-8 AHI data were used to validate the low, middle and high layer water vapor products. The results show that FY-4A AGRI layer water vapor products were with good consistency to all different kinds of products but TERRA/AQUA MODIS. FY-4 will contribute to more accurate understanding and forecasting of China’s weather, climate, environment, and natural disasters. This new generation of Chinese geostationary weather satellites is being developed in parallel with the new generation of geostationary meteorological satellite systems from the international community of satellite providers and is intended to be an important contribution to the global observing system.