Radiometric Inter-Calibration between Himawari-8 AHI and S-NPP VIIRS for the Solar Reflective Bands

Fangfang Yu,Xiangqian Wu

doi:10.3390/rs8030165

Abstract

The Advanced Himawari Imager (AHI) on-board Himawari-8, which was launched on 7 October 2014, is the first geostationary instrument housed with a solar diffuser to provide accurate onboard calibrated data for the visible and near-infrared (VNIR) bands. In this study, the Ray-matching and collocated Deep Convective Cloud (DCC) methods, both of which are based on incidently collocated homogeneous pairs between AHI and Suomi NPP (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS), are used to evaluate the calibration difference between these two instruments. While the Ray-matching method is used to examine the reflectance difference over the all-sky collocations with similar viewing and illumination geometries, the near lambertian collocated DCC pxiels are used to examine the difference for the median or high reflectance scenes. Strong linear relationships between AHI and VIIRS can be found at all the paired AHI and VIIRS bands. Results of both methods indicate that AHI radiometric calibration accuracy agrees well with VIIRS data within 5% for B1-4 and B6 at mid and high reflectance scenes, while AHI B5 is generally brighter than VIIRS by ~6%–8%. No apparent East-West viewing angle dependent calibration difference can be found at all the VNIR bands. Compared to the Ray-matching method, the collocated DCC method provides less uncertainty of inter-calibration results at near-infrared (NIR) bands. As AHI has similar optics and calibration designs to the GOES-R Advanced Baseline Imager (ABI), which is currently scheduled to launch in fall 2016, the on-orbit AHI data provides a unique opportunity to develop, test and examine the cal/val tools developed for ABI.

Highlights

IntroductionAs the first in a series of next-generation geostationary (GEO) weather imagers, the Advanced
As the first in a series of next-generation geostationary (GEO) weather imagers, the AdvancedHimawari Imager (AHI) was successfully launched on-board of Himawari-8 by the Japan MeteorologicalAgency (JMA) on 7 October 2014
To avoid directional reflectance from the sun-glint area caused by the specular reflection, only collocations beyond the sun-glint angle of 25 ̋ (η > 25), which is selected to balance the requirements of sufficient collocation for analysis and, to reduce the sun-glint impact, are used for this analysis

Summary

Introduction

As the first in a series of next-generation geostationary (GEO) weather imagers, the Advanced. It has 16 multispectral bands, including six visible and near infrared (VNIR) and 10 IR bands. The first AHI images of the Earth captured on 18 December 2014 demonstrate a significant increase in high spatial and spectral resolutions, compared to its predecessor MTSAT-series satellite images, which only have one visible and four infrared (IR) bands. A solar diffuser is equipped on a geostationary weather instrument to provide bright reference for the on-orbit radiometric calibration of VNIR bands to reduce the calibration uncertainty. A new design, including double scan mirrors and controlled calibration target temperature, is used to improve the radiometric calibration accuracy of the IR bands. The instrument produces full-disk imagery every 10 min and Remote Sens. 2016, 8, 165; doi:10.3390/rs8030165 www.mdpi.com/journal/remotesensing

Objectives

Results

Conclusion