Algorithms for the classification and characterization of aerosols: utility verification of near-UV satellite observations

Abstract

Aerosol types were characterized and classified using multispectral satellite data. The role of near-UV data in the detection of absorbing aerosols, such as biomass burning aerosols (BBA) or mineral dust particles (DUST), was examined on a global scale. An absorbing aerosol index (AAI) was proposed and defined as the ratio of the satellite-observed radiance (R) at a wavelength of 0.412 μm [R (0.412)] to that at 0.380 μm [R (0.380)] that can also detect nonabsorbing-type aerosols. Initially, the numerical AAI values were estimated for the BBAs and DUST from measurements collected by the Advanced Earth Observing Satellite-2/Global Imager (ADEOS-2/GLI). The Japanese short mission ADEOS-2 carried the GLI instrument with observation channels in the near-UV region. Not only the AAI index but also the short-wavelength infrared measurements were utilized to determine the dust detection index (DDI) defined as the ratio of R (2.210) to R (0.380) in order to discriminate BBAs from DUST. In addition, the AAI and DDI values were evaluated for the detection of clouds. The results allowed the classification criteria for DUST, BBA, other types of aerosols and clouds to be obtained. The Second-Generation Global Imager (SGLI) sensor is onboard the Japanese Global Change Observation Mission-Climate (GCOM-C) (SHIKISAI in Japanese) satellite launched on December 23, 2017. The SGLI has multiple channels (19) including near-UV and polarization sensors in the red and near-IR wavelengths. We also demonstrated the advantages of the SGLI for near-UV and polarization data for aerosol remote sensing. An understanding of aerosol types facilitated subsequent aerosol retrieval. Then, retrieval for classified aerosols was made based on the radiation simulations with multispectral radiance by GLI and polarization measurements by Polarization and Directionality of the Earth's Reflectances (POLDER)-2, respectively, mounted on the ADEOS-2 satellite. The proposed algorithms are expected to be available not only for the analysis of the SGLI data but also for other future missions. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Efficient Detection of Aerosols Above Clouds Utilizing GCOM-C/SGLI Data

“…Nevertheless, we conclude that BBA, and DUST are detected at AAI ≥ 0.83, and AAI ≥ 0.9, respectively. This conclusion coincided with the GLI case treated in the previous work [1]. The values of DDI for BBA were approximately lower than 1.1 at low AOTs and apparently were decreasing with the AOT until AOT=3.…”

“…In this work, the aerosol type classification algorithms proposed in the previous work [1] were applied to a recent Japanese mission GCOM-C/SGLI. The advantages of near-UV data at 0.38µm and 0.41µm wavelength channels collected using the ADEOS-2/GLI launched in 2002 were examined alongside those of GCOM-C/SGLI in 2017.…”

“…The TOMS showed that UV data were effective for the detection of absorbing aerosols such as carbonaceous aerosols or mineral dust [23,36,37]. Our previous works [1,38] were also based on a similar concept in the TOMS-AI (aerosol index). In this study, to follow on from previous works, we named the following index AAI (absorbing aerosol index):…”

“…The shortwave infrared wavelength-channels were used to detect the dust aerosols [40,41]. Therefore, the band with 2.21 µm of GLI was introduced in the previous work [1]. However, in reference to the performance shown in Figure 1, the 1.63 µm band seems to be better than the 2.21 one in the case of SGLI [42].…”

“…This work is an application of our aerosol type classification algorithm mentioned in the previous work [1] to the recent Japanese mission GCOM-C/SGLI measurements. The importance of aerosols is further recognized in reference to global warming and climate change being more serious and imminent.…”