Clear Sky Radiance (CSR)
The CSR (Clear Sky Radiance) product derived from Himawari-8/9 AHI (Advanced Himawari Imager) observation provides area-averaged brightness temperatures for cloud-free pixels. The CSR data is calculated for each 16 x 16 infrared pixel box corresponding to approximately 32 x 32 km2 resolution at the sub-satellite point for NWP (Numerical Weather Prediction) global assimilation systems. In addition to ordinary clear pixels determined by the fundamental cloud product (cloud mask), cloudy pixels in which the contribution of cloud top emission to total radiance is negligible are also regarded as clear in the Himawari-8/9 CSR calculation. This increases the number of clear pixels for AHI bands with strong absorption (e.g., water vapor bands). Cloud top height is also determined by the fundamental cloud product. The Himawari CSR product is provided in Binary Universal Form for data Representation (BUFR) via the Global Telecommunication System (GTS). NWP centers can use the Himawari CSR product in their operational assimilation systems.
Meteorological Satellite Center Technical Note No.61
Sample below are CSR at 03 UTC on 1 June 2015.