Validation of Himawari-8/AHI Radiometric Calibration Based on Two Years of In-Orbit Data

Abstract

The new geostationary (GEO) meteorological satellite of the Japan Meteorological Agency (JMA), Himawari-8, entered operation on 7 July 2015. Himawari-8 features the new 16-band Advanced Himawari Imager (AHI), whose spatial resolution and observation frequency are improved over those of its predecessor MTSAT-series satellites. These improvements will bring about unprecedented levels of performance in nowcasting services and short-range weather forecasting systems. In view of the essential nature of navigation and radiometric calibration in fully leveraging the imager's potential, this study reports on the current status of calibration for the AHI. Image navigation is accurate to within 1 km, and band-to-band coregistration has also been validated. Infrared (IR) band calibration is accurate to within 0.2 K with no significant diurnal variation and is being validated using an approach developed under the Global Space-based Inter-Calibration System (GSICS) framework. Validation approaches are currently being tested for the visible and near-IR (NIR) bands. Two such approaches were compared and found to produce largely consistent results.

Pseudo-thermal anomalies in the shortwave infrared bands of the Himawari-8 AHI and their correction for volcano thermal observation

“…1 and 2 originated from stray light. The results of our research show that those effects exert definite influence upon the nighttime images of the 1.6-µm and 2.3-µm bands over very long periods during each yearabout 6 months, as suggested by Okuyama et al (2018). Examples of the stray light that affects the AHI images are shown in Fig.…”

“…The most useful clue for the cause of the anomaly is the timing of its appearance. The fact that the pseudo-thermal anomaly appears in the vernal and autumn equinox periods suggests that it is closely related to earth eclipse (Okuyama et al 2018), that is, when a geostationary satellite, such as Himawari-8, enters the shadow of the earth (Fig. 3a).…”

“…Himawari-8 is a meteorological satellite operating at a geostationary position approximately 35,800 km above the equator at a longitude of 140.7°E. It carries a newly developed sensor, the Advanced Himawari Imager (AHI), that operates in 16 spectral bands from the visible to thermal infrared (Japan Meteorological Agency 2015a; Okuyama et al 2018). This instrument has great advantages for carrying out volcano thermal observations (Kaneko et al 2018).…”

In-Flight Radiometric Calibration of Compact Infrared Camera (CIRC) Instruments Onboard ALOS-2 Satellite and International Space Station

“…The radiometric accuracies of the MTSAT-2 Imager and Himawari-8/AHI have been validated using high spectral resolution sounders such as the Atmospheric Infrared Sounder (AIRS) onboard the Aqua satellite [23] or the Infrared Atmospheric Sounder Interferometer (IASI) onboard the MetOp satellite [24] through the Global Space-based Inter-Calibration System (GSICS) [25]. As for the MTSAT-2 Imager, Hewison et al showed that the IR channels (IR1 at 10.8 µm, and IR2 at 12 µm) had stable biases with the averages of +0.08 K for IR1 and +0.10 K for IR2 for two years from June 2010 [25], while Okuyama et al mentioned that the biases of some IR channels (e.g., IR2) tended to increase to 1.5 K at nighttime around the eclipse season, whereas those seen during the daytime were a tenth of these values [26]. As for Himawari-8/AHI, Okuyama et al showed that the IR bands (bands 7 to 16) were calibrated within 0.2 K with no significant diurnal variation [26].…”

“…As for the MTSAT-2 Imager, Hewison et al showed that the IR channels (IR1 at 10.8 µm, and IR2 at 12 µm) had stable biases with the averages of +0.08 K for IR1 and +0.10 K for IR2 for two years from June 2010 [25], while Okuyama et al mentioned that the biases of some IR channels (e.g., IR2) tended to increase to 1.5 K at nighttime around the eclipse season, whereas those seen during the daytime were a tenth of these values [26]. As for Himawari-8/AHI, Okuyama et al showed that the IR bands (bands 7 to 16) were calibrated within 0.2 K with no significant diurnal variation [26].…”