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Aerosol scattering effects on water vapor retrievals over the Los Angeles Basin

Zeng, Zhao-Cheng and Zhang, Qiong and Natraj, Vijay and Margolis, Jack S. and Shia, Run-Lie and Newman, Sally and Fu, Dejian and Pongetti, Thomas J. and Wong, Kam W. and Sander, Stanley P. and Wennberg, Paul O. and Yung, Yuk L. (2017) Aerosol scattering effects on water vapor retrievals over the Los Angeles Basin. Atmospheric Chemistry and Physics, 17 (4). pp. 2495-2508. ISSN 1680-7324. doi:10.5194/acp-17-2495-2017.

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In this study, we propose a novel approach to describe the scattering effects of atmospheric aerosols in a complex urban environment using water vapor (H_2O) slant column measurements in the near infrared. This approach is demonstrated using measurements from the California Laboratory for Atmospheric Remote Sensing Fourier Transform Spectrometer on the top of Mt. Wilson, California, and a two-stream-exact single scattering (2S-ESS) radiative transfer (RT) model. From the spectral measurements, we retrieve H_2O slant column density (SCD) using 15 different absorption bands between 4000 and 8000 cm^(−1). Due to the wavelength dependence of aerosol scattering, large variations in H_2O SCD retrievals are observed as a function of wavelength. Moreover, the variations are found to be correlated with aerosol optical depths (AODs) measured at the AERONET-Caltech station. Simulation results from the RT model reproduce this correlation and show that the aerosol scattering effect is the primary contributor to the variations in the wavelength dependence of the H_2O SCD retrievals. A significant linear correlation is also found between variations in H_2O SCD retrievals from different bands and corresponding AOD data; this correlation is associated with the asymmetry parameter, which is a first-order measure of the aerosol scattering phase function. The evidence from both measurements and simulations suggests that wavelength-dependent aerosol scattering effects can be derived using H_2O retrievals from multiple bands. This understanding of aerosol scattering effects on H_2O retrievals suggests a promising way to quantify the effect of aerosol scattering on greenhouse gas retrievals and could potentially contribute towards reducing biases in greenhouse gas retrievals from space.

Item Type:Article
Related URLs:
URLURL TypeDescription
Zeng, Zhao-Cheng0000-0002-0008-6508
Zhang, Qiong0000-0002-8762-0557
Natraj, Vijay0000-0003-3154-9429
Shia, Run-Lie0000-0003-1911-3120
Newman, Sally0000-0003-0710-995X
Pongetti, Thomas J.0000-0001-9465-0853
Sander, Stanley P.0000-0003-1424-3620
Wennberg, Paul O.0000-0002-6126-3854
Yung, Yuk L.0000-0002-4263-2562
Additional Information:© Author(s) 2017. This work is distributed under the Creative Commons Attribution 3.0 License. Received: 08 Jun 2016 – Discussion started: 20 Jun 2016. Revised: 27 Jan 2017 – Accepted: 27 Jan 2017 – Published: 17 Feb 2017. We thank M. Gunson and A. Eldering for stimulating discussions and support, and M. Gerstell for proofreading the manuscript. Part of the research in this study was performed at the Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech), under a contract with the National Aeronautics and Space Administration (NASA). Support from the Caltech KISS Megacity project, the NIST GHG and Climate Science Program and NASA’s Carbon Cycle Science Program through the JPL is gratefully acknowledged. Zhao-Cheng Zeng was supported by a postgraduate studentship for overseas academic exchange from the Chinese University of Hong Kong. We thank Jochen Stutz and his staff for their effort in establishing and maintaining the AERONET Caltech site. We also thank the anonymous reviewers whose comments helped improve the paper significantly. Data availability: The AERONET data for this paper can be downloaded online (; CLARS-FTS data are available from the authors upon request. The Supplement related to this article is available online at doi:10.5194/acp-17-2495-2017-supplement. The copyright of individual parts of the supplement might differ from the CC-BY 3.0 licence. The authors declare that they have no conflict of interest.
Group:Keck Institute for Space Studies, Astronomy Department, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
Keck Institute for Space Studies (KISS)UNSPECIFIED
National Institute of Standards and Technology (NIST)UNSPECIFIED
Chinese University of Hong KongUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20170330-153453156
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Official Citation:Zeng, Z.-C., Zhang, Q., Natraj, V., Margolis, J. S., Shia, R.-L., Newman, S., Fu, D., Pongetti, T. J., Wong, K. W., Sander, S. P., Wennberg, P. O., and Yung, Y. L.: Aerosol scattering effects on water vapor retrievals over the Los Angeles Basin, Atmos. Chem. Phys., 17, 2495-2508, doi:10.5194/acp-17-2495-2017, 2017.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75555
Deposited By: George Porter
Deposited On:30 Mar 2017 23:16
Last Modified:02 Jun 2023 01:37

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