Characterization of Himawari-8/AHI to Himawari-9/AHI infrared observations continuity

ABSTRACT

As the ‘twin imagers’, Himawari-8/AHI and Himawari-9/AHI are both the new generation imagers operated by the Japan Meteorological Agency (JMA). After more than 7 years of operation, Himawari-8/AHI turned into stand-by status and Himawari-9/AHI began operation as the successor. To continuous users of both imagers, it is essential to characterize continuity of Himawari-8/AHI to Himawari-9/AHI observations, which can provide beneficial information to quantitative retrieval and satellite assimilation algorithm developer. In this research, cross-comparison are performed to Himawari-8/AHI and Himawari-9/AHI infrared (IR) observations, and ‘observation minus background (O - B)’ characters of two imagers under clear-sky condition over ocean are also compared. The results are as follows: 1) Himawari-8/AHI and Himawari-9/AHI IR observations are in good consistency with largest absolute bias less than 1.437 K and RMSE below 1.663 K. Biases and RMSEs for Himawari-8/AHI and Himawari-9/AHI channel 7 show obvious diurnal variation character and RMSEs for all channels have evident temporal cycle variation characteristics, with cycle time of about 10 days; 2) IR observations of Himawari-8/AHI are more closed to RTTOV simulations under clear-sky condition than those of Himawari-9/AHI, especially for channels 7, 9 and 16. Dependence of O – B biases and RMSEs for two imagers IR channels on satellite scan angles are almost identical.

KEYWORDS:

• Himawari-8/AHI
• Himawari-9/AHI
• infrared observations continuity

Acknowledgements

The authors would like to thank the JAXA for providing Himawari-8/AHI and Himawari-9/AHI Level 1 Products (https://ftp.ptree.jaxa.jp, accessed on 15 March 2023), NESDIS for providing Himawari-8 Cloud Mask Product (https://noaa-himawari8.s3.amazonaws.com/, accessed on 18 March 2023), the ECMWF for providing ERA5 reanalysis (https://cds.climate.copernicus.eu, accessed on 25 March 2023) and RTTOV source code (https://nwp-saf.eumetsat.int/, accessed on 28 March 2023), and the NOAA for providing MODIS land cover product (https://www.earthdata.nasa.gov/, accessed on 28 March 2023).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 92037000), the Balance Funding Project of National Meteorological Information Centre (Grant No. NMICJY202306) and the Fengyun Application Pioneering Project (Grant No. FY-APP-2021.0207, FY-APP-2022.0608).