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Remote sensing of aerosol properties from multi-wavelength and multi-pixel information over the ocean

Remote sensing of aerosol properties from multi-wavelength and multi-pixel information over the ocean

Authors :
C. Shi
M. Hashimoto
T. Nakajima
Source :
Atmospheric Chemistry and Physics, Vol 19, Pp 2461-2475 (2019)
Publication Year :
2019
Publisher :
Copernicus Publications, 2019.

Abstract

In this study, we investigate the feasibility of a multi-pixel scheme in the inversion of aerosol optical properties for multispectral satellite instruments over the ocean. Different from the traditional satellite aerosol retrievals conducted pixel by pixel, we derive the aerosol optical thickness (AOT) of multiple pixels simultaneously by adding a smoothness constraint on the spatial variation of aerosols and oceanic substances, which helps the satellite retrieval, with higher consistency from pixel to pixel. Simulations are performed for two representative oceanic circumstances, open and coastal waters, as well as the land–ocean interface region. We retrieve the AOT for fine, sea spray, and dust aerosols simultaneously using synthetic spectral measurements, which are from the Greenhouse Gases Observing Satellite and Thermal and Near Infrared Sensor for Carbon Observation – Cloud and Aerosol Imager (GOSAT∕TANSO-CAI), with four wavelengths ranging from the ultraviolet to shortwave infrared bands. The forward radiation calculation is performed by a coupled atmosphere–ocean radiative transfer model combined with a three-component bio-optical oceanic module, where the chlorophyll a concentration, sediment, and colored dissolved organic matter are considered. Results show that accuracies of the derived AOT and spectral remote-sensing reflectance are both improved by applying smoothness constraints on the spatial variation of aerosol and oceanic substances in homogeneous or inhomogeneous surface conditions. The multi-pixel scheme can be effective in compensating for the retrieval biases induced by measurement errors and improving the retrieval sensitivity, particularly for the fine aerosols over the coastal water. We then apply the algorithm to derive AOTs using real satellite measurements. Results indicate that the multi-pixel method helps to polish the irregular retrieved results of the satellite imagery and is potentially promising for the aerosol retrieval over highly turbid waters by benefiting from the coincident retrieval of neighboring pixels. A comparison of retrieved AOTs from satellite measurements with those from the Aerosol Robotic Network (AERONET) also indicates that retrievals conducted by the multi-pixel scheme are more consistent with the AERONET observations.

Subjects

Subjects :
Physics
QC1-999
Chemistry
QD1-999

Details

Language :
English
ISSN :
16807316 and 16807324
Volume :
19
Database :
Directory of Open Access Journals
Journal :
Atmospheric Chemistry and Physics
Publication Type :
Academic Journal
Accession number :
edsdoj.80c37570212244168cadd18ec32680c9
Document Type :
article
Full Text :
https://doi.org/10.5194/acp-19-2461-2019