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Aerosol Layer Height over Water via Oxygen A-Band Observations from Space: A...

Davis, A. B., and O. V. Kalashnikova (2019), Aerosol Layer Height over Water via Oxygen A-Band Observations from Space: A Tutorial, In: Kokhanovsky A. (eds) Springer Series in Light Scattering. Springer Series in Light Scattering. Springer, 3, 133-166, doi:10.1007/978-3-030-03445-0_4.

In this tutorial, we illustrate the development of a modeling framework for a currently important remote sensing challenge in aerosol characterization, specifically, aerosol profiling using a passive approach rather than a lidar for optically thin layers.  We begin with a simplified physics-based model for the observed quantities, namely, differential optical absorption spectroscopy (DOAS) ratios that measure the amount of absorption by di-oxygen molecules along the multiple paths that sunlight can take between the extra-atmospheric source and back to a space-based detector via scattering.  Key for absorption by a major gas like O2 is path length, and we explore two ways of modulating it: moderate resolution spectroscopy (hence one DOAS ratio per sampled wavelength), and multi-angle observations using only one ``in-band'' channel and a ``reference'' counterpart (hence a single DOAS ratio per sampled view angle).  The radiative transfer physics is used to feed an optimal estimation apparatus based on mathematical statistics that is used to formally quantity the aerosol profile information content of the proposed observations.  This formalism factors in the potential for redundancy in the the measurements as well as instrument noise, uncertainty in required aerosol properties, and prior knowledge about the parameterized aerosol profile.  We conclude that for the instrument configurations under consideration, which are inspired by the future NASA Plankton, Aerosol, Cloud, and ocean Ecosystem (PACE) mission, one can retrieve reliably only the height of the aerosol layer and not its thickness for low aerosol optical depth.

PDF of Publication: 
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Research Program: 
Radiation Science Program (RSP)
Funding Sources: 
ROSES - PACE Science Team